1997 FIAT PUNTO Heating
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3*2 Cooling, heating and ventilation systems
Testing 7 A rough test of the thermostat may be made by suspending it with a piece of siring in a container full of water. Heat tho water to bring it to the boii and observe the movement of the vaive shaft through the inlet port (see illustrations). 6 The thermostat valve must be fully open, by the time the water boils. If not, renew the complete IhermOstat/housIng assembly. 9 If a thermometer is available, the precise opening temperature of the thermostat may be determined; compare with the figures given in the Specifications. The opening temperature Is also marked on the thermostat housing. 10 Note that a thermostat which falls to close completely as ihe water cools must also be renewed.
Refitting 11 Ensure that the cylinder head and thermostat housing mating surfaces are
completely clean and free from ail traces of Ihe old gasket material. 12 Lay a new gasket In position on the cylinder head, then fit the thermostat housing and Insert retaining bolts, tightening them securely.
Caution: Do not over-tlghten tho retaining bolts, as tho alloy casting could easily be damaged 13 Where applicable, transfer the cooling fan switch and coolant temperature sensor to the new housing. 14 Refit the coolant hose(s) to the ports on the thermostat housing and lighten the clips securely. 15 Where applicable, refit the harness/hose support bracket to the thermostat housing and tighten the bolts securely. Also refit the air cleaner and Inlet ducts as described in Chapter 4B 15 Refill the cooling system as described in Chapter 1A or 1B.
5 Electric cooling fan(s) -testing, removal and refitting ^
Testing 1 Detailed fault diagnosis should be camw out by a Rat dealer using dedicated tesl equipment, but basic diagnosis can be car&c out as follows. 2 If the fan does not appear to work, run if* engine until normal operating temperature s reached, Ihen allow It to idle. The fan shouldcti In within a few minutes (before lite temperalure gauge needle enters the red section), il nol. switch off the engine and disconnect tfie cooling fan motor wiring connector. 3 The motor can be tested by disconnecting it from the wiring loom, and connecting a 12? volt supply directly to It. The motor should operate - if not. the motor, or the motor wiring. Is faulty.
frotf heater from cylinder head mdotor
4.7b Thermostat operation in the fully closed position (diesel engine)
from neoier Irom cylinder head radiator
4.7c Thermostat operation in the fully open position (diesel engine)
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4 If the motor operates when tested as described, (he fault must lie In the engine wring harness or the temperature sensor. The temperature sensor/switch can be tested as described in Section 6. Any further fault Diagnosis should be referred to a suitably-equipped Fiat dealer - do not attempt to test
Ihe
electronic control unit.
Removal 5 Disconnect the battery negative terminal (refer to D/scon oecf/ng the battery in the Reference Section of this manual). 6 On diesel engine models, unbolt the relay bracket from the side of the battery tray to improve access. On 1242 cc {16-valve) petrol engine models, remove the air cleaner and
inset
ducts as described in Chapter 4B. 1 Disconnect the motor wiring connectorfs). 8 Unbolt the shroud from the rear of the ratiator. then lift out the cooling fan assembly. Refitting 9 Refitting is a reversal of removal
6 Cooling fan switch -testing, removal and refitting ^
Testing 1 The switch is threaded into the lower left
nand
comer of the radiator. 2 The switch can be tested by removing it,
and
checking that the switching action occurs
at
the correct temperature {heat the sensor in a container of water, and monitor the temperature with a thermometer). 3 There should be no continuity between the switch terminals, until Ihe specified cooling fan cut-In temperature Is reached, when continuity (and zero resistance) should exist between the terminals.
Removal 4 Disconnect the battery negative terminal refer to Disconnecting the battery in the Reference Section of this manual). 5 Allow the engine to cool completely, then drain the cooling system as described in Chapter 1Aor 1B. 6 Disconnect the wiring plug from the sensor.
bolts...
7 Carefully unscrew the sensor and. whore applicable, recover the sealing ring. Refitting 8 If the sensor was originally fitted using sealing compound, clean the sensor threads thoroughly, and coat them with fresh sealing compound. 9 If the sensor was originally fitted using a sealing ring, use a new sealing ring on refitting. 10 Refitting is a reversal of removal, but refill the cooling system as described in Chapter 1A or 18. 11 On completion, start the engine and run it until it reaches normal operating temperature. Continue to run the engine until the cooling fan cuts in and out correctly.
7 Coolant pump • & removal, inspection 5 and refitting
Removal
Petrol engine models 1 Disconnect the battery negative terminal (refer to Disconnecting the battery in the Reference Section of this manual). 2 Drain the cooling system and remove the auxiliary drivebett(s) as described In Chapter 1 A. 3 Remove the timing belt as described In Chapter 2A or 28. 4 Unscrew the securing bolts/nuts, and withdraw the coolant pump (see illustrations).
7.9b ... and lift off the pulley (diesel engine)
(petrol engine) If the pump Is stuck, tap it gently using a soft-faced mallet - do not lever between the pump and cylinder block mating faces.
Diesel engine models 5 Disconnect the battery negative terminal (refer to D/s connecting the battery in the Reference Section of this manual). 6 Drain the cooling system as described in Chapter 1B. 7 Remove the auxiliary drivebelt(s) as descnbed In Chapter 1B. 6 On models fitted with power steenng, refer to Chapter 10 and remove the power steering pump from its mountings; this can be achieved without disconnecting the power steering fluid hoses from the pump. Tie the pump away from the work area, taking care to avoid kinking the fluid hoses. 9 Unscrew the securing bolts, and remove the coolant pump pulley. It will be necessary to counterhold the pulley In order to unscrew the bolts, and this is most easily achieved by wrapping an old drivebelt tightly around the pulley to act in a similar manner to a strap 3 wrench. Alternatively, a stout screwdriver can be braced between two of the pulley bolts while the third is slackened (see illustrations). 10 Disconnect ihe bypass hoses from the coolant pump outlet stubs. 11 Unscrew the securing bolts, and withdraw the coolant pump assembly. Note that the pump must be detached from the transfer pipe than runs behind the cylinder block to the thermostat housing (see illustration). The pipe is a push fit in the port on the rear of the coolant pump
7.11 Removing the coolant pump assembly (diesel engine)
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3*2 Cooling, heating and ventilation systems
12 If tho pump is stuck, tap It gently using a soft-faced mallet • do not lever between the pump and cylinder block mating faces.
Inspection 13 Check the pump body and impeller for signs of excessive corrosion. Turn the impeller, and check for stiffness due to corrosion, or roughness due to excessive end play. 14 Check the clearance between the pump Impeller and the casing using a feeler blade (see Illustration). If the clearance is different to that given In the Specifications, the pump must be renewed. No spare components are available; the pump can only be renewed as a complete assembly. 15 On diesel engine models, remove the O-rlng at the end ol the transfer pipe, which runs behind Ihe cylinder block and fits Into the rear of the coolant pump. A new O-rlng should be fitted as a matter of course.
Refitting
Petrol engine models 16 Commence refitting by thoroughly cleaning all traces of sealant from the mating faces of the pump and cylinder block/pump housing. 17 Apply a continuous bead of sealant {liquid gasket) to the cylinder block mating face of the pump, taking care not to apply excessive sealant, which may enter the pump itself (see Illustration). 18 Place the pump In position In Its housing, then refit and lighten the bolts/nuts to the specified torque. 19 Refit the liming belt as described In Chapter 2A or 28. 20 Refit the auxiliary drivebeltfs) and refill the cooling system as described in Chapter
t
A. 21 Reconnect Ihe battery negative terminal. Diesel engine models 22 Commence refitting by thoroughly cleaning all traces of old gasket from the mating faces of the pump housing and cylinder block. 23 Place a new gasket in position on (he cylinder block, locate the pump in position, then refit and tighten the bolts (see
7.17 On petrol engine models, apply a continuous bead of sealant (liquid gasket) to the pump mating face
pump Impeller and the casing using a feeler blode (diesel engine) illustration). Ensure that the end of the coolant transfer pipe seats firmly In tho port at the rear of the coolant pump, without displacing the O-ring seal. 24 Refit Ihe pump pulley, then refit the securing bolts and tighten to the specified torque. Counterhofd the pulley using the same method employed during removal. 25 Where applicable, refit the power steering pump with reference to Chapter 10. 26 Refit and tension the auxiliary drivebelt(s) as described in Chapter 18. 27 Refill (he cooling system as desenbed in Chapter 1B. 28 Reconnect the battery negative terminal.
8 Heater/ventilation components - § removal and refitting
Complete heater assembly
A
Warning: On mode's fitted with air conditioning, do not attempt to remove the cooling unit, which Is located between the heater blower motor casing and the main heater assembly. Romovat of the cooling unit entails disconnection of refrigerant lines - refer to Section 10 for precautions to be observed.
rfJS
8.3 Slacken the clips (arrowed) and detach the heater unit coolant hoses from the ports at the bulkhead
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3*2 Cooling, heating and ventilation systems
Heater matrix Removal 10 Remove the complete heater assembly as described previously in this Section. 11 Slacken and remove the securing screws, then withdraw the heater matrix from the tester assembly casing. Refitting 12 Refitting is a reversal of removal; refit Ihe neater assembly as described previously in
this
Section.
Heater blower motor
Removal 13 Disconnect the battery negative terminal {refer to Disconnecting the battery in the Reference Section of this manual). 14 Unplug the wiring from the blower motor
al the
connector. 15 Working in the passenger front footwell, under the glovebox. remove the securing grows and lower the blower motor and rotor assembly from Its casing (see illustration). Refitting
16 Refitting is a reversal of removal.
Heater blower motor resistor
Removal 17 The resistor is located at the bottom of the heater casing, behind the blower motor. 18 Disconnect the battery negative terminal (refer to O/sconnecf/ng the battery in the Reference Section of this manual). 19 For improved access, remove the blower motor as described in the previous sub-Section. 20 Disconnect the wiring plug from the resistor. 21 Working under the glovebox. remove the two securing screws, and withdraw the resistor from the blower unit case (see lustrations).
8.15 Removo the securing screws and lower the blower motor and rotor assembly from its casing Refitting 22 Refining Is a reversal of removal.
Heater control panel
Removal 23 Pull the ventilation fan speed control knob from the panel. 24 Unscrew and remove the three screws securing the panel cover. Two screws are under the lower edge of the panel, whilst Ihe remaining screw is located in the ventilation fan speed control knob recess. Remove the panel. 25 Unscrew and remove the four screws securing the control panel to the facia. The screws are located in each comer of the panel. 26 Remove the facia as described in Chap-ter 11. 27 Make a careful note of the cable and electrical connections. Unscrew the cable clamps and unclip the inner cables from the controls. Unplug the ventilation fan speed control. 28 Unclip and remove the control panel from the heater distributor box assembly. Refitting 29 Refitting is a reversal of removal.
9 Air conditioning system -general Information and precautions
General information An air conditioning system is available on certain models. It enables the temperature of Incoming air to be lowered, and also dehumidifies the air, which allows rapid demisting and increased comfort. The cooling side of the system works In the same way as a domestic refrigerator. Refrigerant gas is drawn into a belt-driven compressor where the increase In pressure causes the refrigerant gas to turn to liquid. It then passes through a condenser mounted on the front of the radiator, where it is cooled. Tho liquid then passes through an expansion vaive to an evaporator, where it changes from liquid under high pressure to gas under low pressure. This change is accompanied by a drop in temperature, which cools the evaporator and hence the air passing over it. The refrigerant returns to the compressor, and the cycle begins again. The air bfown through the evaporator passes to the air distribution unit where it is mixed, if required, with hot air blown through the heater matrix to achieve the desired temperature in the passenger compartment. The heating side of ihe system works in the same way as on models without air conditioning (see Section 8). The system Is electronically-controlled. Any problems with the system should be referred to a Fiat dealer.
Precautions With an air conditioning system. It is necessary to observe special precautions whenever dealing with any part of the system, or its associated components. If for any reason the system must be disconnected, it Is
8.21a Remove the two securing screws (arrowed)... ,21b ... and withdraw the resistor from the blower unit case
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3*2 Cooling, heating and ventilation systems
essential that you entrust this task to your Flat dealer or a refrlgeralion engineer.
A
Warning: The refrigeration circuit contains a liquid refrigerant and
H
Is dangerous to disconnect any part of the system without specialist knowledge and equipment. The refrigerant is potentially dangerous, and should only be handled by qualified persons. If it is splashed onto tha skin, It can cause severe frostbite, tt Is not Itself poisonous, but In the presence of a naked flame (Including a cigarette), it forms a
poisonous gas. Uncontrolled discharging of the refrigerant is dangerous and potentially damaging to the environment.
10 Air conditioning components ^S - removal and refitting J
Note: Do not operate the air conditioning system If it is known to be short of refrigerant, as this may damage the compressor. 1 The only operation which can be carried
out easily without discharging the refrigerant is renewal of the auxiliary (compressor) drivebelt - this procedure Is described in Chapter 1A or 1B. All other operations must be referred to a Fiat dealer or an air conditioning specialist. 2 If necessary for access to other com-ponents, the compressor can be unbolted and moved aside, without disconnecting its flexible hoses, after removing the drivebelt.
A
Warning: Do not attempt to open the refrigerant circuit. Refer to
the
precautions given in Section 9.
expert22 a/ia http://rutracker.org
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4D«1
Chapter 4 Part D:
Exhaust and emission control systems
Contents
Catalytic converter - general Information and precautions 7 Crankcase emission system • general information 3 Evaporative loss emission control system • information and component renewal 2
Degrees of difficulty
Exhaust manifold - removal and refitting 5 Exhaust system - general information and component renewal .... 6 General information 1 Lambda oxygen sensor - removal and refitting 4
Easy, suitable
tor novice with fittie ^
1 experience
Fairly easy, suitable for beginner with ^ some experience ^
Fairiy dfficult, lb suitable for competent ^ DIY mechanic ^
Difficult, suitable for experienced DIY ^ mechanic
Very difficult, ^ suitable far expert DIY or professional
Specifications
Torque wrench settings Exhaust down pipe to manifold Exhaust manifold Exhaust system mounting Exhaust to catalytic converter: M8 M10x1.25
Nm Ibfft 24 18 24 18 27 20
24 18 40 30 53 39
1 General information
Emission control systems All petrol engine models use unleaded petrol and are controlled by engine management systems that are 'tuned' to give the best compromise between driveability. luel consumption and exhaust emission production. In addition, a number of systems are fitted that help to minimise other harmful emissions: a crankcase emission-control system (petrol models only) that reduces the release of pollutants from the crankcase, an evaporative loss emission control system (petrol models only) to reduce the release of hydrocarbons from the fuel tank, a catalytic converter (petrol and diesel models) to reduce exhaust gas pollutants, and an Exhaust Gas Recirculation (EGR) system (turbo diesel models only) to reduce exhaust emissions. Crankcase emission control To reduce the emission of unburned hydrocarbons from the crankcase Into the atmosphere, the engine is sealed and the blow-by gases and oil vapour are drawn from inside the crankcase, through a flame trap.
into the inlet tract to be burned by the engine during normal combustion. Under conditions of high manifold depression (idling, deceleration) the gases will by sucked positively out of the crankcase. Under conditions of low manifold depression (acceleration, full-throttle running) ihe gases are forced out of the crankcase by the (relatively) higher crankcase pressure: if the engine is worn, the raised crankcase pressure (due to increased blow-by) will cause some of the flow to return under all manifold conditions. Exhaust emission control -petrol models To minimise the amount of pollutants which escape Into the atmosphere, a catalytic converter is fitted In the exhaust system. The fuel system is of the closed-loop type, in which a Lambda (or oxygen) sensor In the exhaust system provides the engine management system ECU with constant feedback, enabling the ECU to adjust the air/fuel mixture to optimise combustion. The Lambda sensor has a heating element built-in that Is controlled by the ECU through the Lambda sensor relay to quickly bring the sensor's tip to Its optimum operating temperature. The sensor's tip Is sensitive to oxygen and relays a voltage signal to the ECU
that varies according on the amount of oxygen In the exhaust gas. If the inlet air/fuel mixture is too rich, the exhaust gases are low in oxygen so the sensor sends a low-voltage signal, the voltage rising as the mixture weakens and the amount of oxygen rises In the exhaust gases. Peak conversion efficiency of all major pollutants occurs if the inlet air/fuel mixture Is maintained at the chemlcally-con*ect ratio for the complete combustion of petrol of 14.7 parts (by weight) of air to
1
part of fuel (the stoichiometric ratio). The sensor output voltage alters in a large step at this point, the ECU using the signal change as a reference point and correcting the Inlet air/fuel mixture accordingly by altering the fuel Injector pulse width. Exhaust emission control -diesel models An oxidation catalyst is fitted in the exhaust system of all diesel engine models. This has the effect of removing a large proportion of the gaseous hydrocarbons, carbon monoxide and particulates present in the exhaust gas. An Exhaust Gas Recirculation (EGR) system Is fitted to all turbo diesel engine models. This reduces the level of nitrogen oxides produced during combustion by Introducing a proportion of the exhaust gas back into the inlet manifold, under certain engine operating
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5A«2 Starting and charging systems
1 General information and precautions
General information The engine electrical system consists mainly of the charging and starting systems. Because of their engine-related functions, these components are covered separately from the body electrical devices such as the Ilght3, Instalments, etc (which are covered In Chapter 12). On petrol engine models refer to Part B for information on the ignition system, and on diesel models refer to Part C for information on the preheating system. The electncal system Is of 12-volt negative earth type. The battery fitted as original equipment is of maintenance* free (sealed for life} type and Is charged by the alternator, which is belt-driven from the crankshaft pulley. If a non-original battery is fitted It may be of standard or low maintenance type. The starter motor is of the pre-engaged type Incorporating an integral solenoid. On starting, the solenoid moves the drive pinion into engagement with the flywheel ring gear before the starter motor is energised. Once the engine has started, a one-way clutch prevents the motor armature being driven by the engine until the pinion disengages from the flywheel.
Precautions Further details of the various systems are given In the relevant Sections of this Chapter. While some repair procedures are given, the usual course of action is to renew the component concerned. The owner whose interest extends beyond mere component renewal should obtain a copy of the Automobile Electrical & Electronic Systems Manual, available from the publishers of this manual It Is necessary to take extra care when working on the electrical system to avoid damage to semiconductor devices (diodes and transistors), and to avoid the risk of personal injury. In addition to the precautions given in Safety first! at the beginning of this manual, observe the following when working on the system: Always remove rings, watches, etc before working on the electrical system. Even with the battery disconnected, capacitlve discharge could occur If a component's live terminal is earthed through a metal object. This could cause a shock or nasty bum. Do not reverse the battery connections. Components such as the alternator, electronic control units, or any other components having semi-conductor circuitry could be irreparably damaged. If the engine is being started using jump leads and a slave battery, connect the batteries positive-to-posibve and negative-to-
negative (see Jump starting). This also applies when connecting a battery charger but In this case both of the battery terminals should first be disconnected. Never disconnect the battery terminals, the alternator, any electrical wiring or any test Instalments when the engine Is running. Do not allow the engine to turn the alter-nator when the alternator Is not connected. Never test for alternator output by flashing the output lead to earth. Never use an ohmmeter ot the type Incorporating a hand-cranked generator for circuit or continuity testing. Always ensure that the battery negative lead is disconnected when working on the electrical system. Before using electric-arc welding equipment on the car, disconnect the battery, alternator and components such as the fuel Injection/ignition electronic control unit to protect them from the risk of damage. Several systems fitted to the vehicle require battery power to be available at all times, either to ensure their continued operation (such as the clock) or to maintain control unit memories or security codos which would be wiped if the battery were to be disconnected. To ensure that there are no unforeseen consequences of this action. Refer to Disconnecting the battery In the Reference Section of this manual for further Information.
2 Battery- % testing and charging
Standard and tow maintenance battery - testing 1 If the vehicle covers a small annual mileage, it is worthwhile checking the specific gravity of the electrolyte every three months to determine the state of charge of the battery. Use a hydrometer to make the check and compare the results with the following table, Note that the specific gravity readings assume an electrolyte temperature of 15*C (60'F); for every 10*C (18°f) below 158C (60aF) subtract 0.007, For every 108C (16'F) above 15"C (60'F) add 0.007. Ambient temperature Above 26"C Below 25DC Charged 1,210 to 1£30 1,270 to 1.290 70% charged 1.170to1.l90 1.230to1.250 Discharged 1.050toJ.070 1.110 to 1.130 2 If the battery condition is suspect, first check the specific gravity of electrolyte In each cell. A variation of 0.040 or more between any cells indicates loss of electrolyte or deterioration of the internal plates. 3 If the specific gravity variation is 0.040 or more, the battery should be renewed. If the cell variation Is satisfactory but the battery is discharged, it should be charged as described later in this Section.
Maintenance-free battery -testing 4 In cases where a sealed tor life maintenance-free battery is fitted, topplng-up and testing of the electrolyte in each cell Is not possible. The condition of the battery can therefore only be tested using a battery condition Indicator or a voltmeter. 5 Certain models may be fitted with a maintenance-free battery with a built-in charge condition Indicator. The indicator Is located in the top of the battery casing, and indicates the condition of the battery from its colour. If the Indicator shows green, then the battery is In a good state of charge. If the Indicator turns darker, eventually to black, then the battery requires charging, as described later in this Section. If Ihe indicator shows clear/yellow, then the electrolyte level in Ihe battery is too low to allow further use, and tho battery should be renewed. Do not attempt to charge, load or Jump start a battery when the indicator shows dear/yellow. 6 If testing the battery using a voltmeter, connect the voltmeter across the battery and compare the result with those given In the Specifications under 'charge condition'. The test is only accurate if the battery has not been subjected to any kind of charge for the previous six hours. If this is not the esse, switch on the headlights for 30 seconds, then wait four to five minutes baforo testing the battery after switching off the headlights. All other electrical circuits must be switched off, so check that the doors and tailgate are fully shut when making the test, 7 It the voltage reading Is less than 12.2 voHs, then the battery Is discharged, whilst a reading of 12.2 to 12.4 volts indicates 8 partially discharged condition. 6 If the battery Is to be charged, remove It from the vehicle (Section 3) and charge it as described later In this Section.
Standard and low maintenance battery - charging Note: The following is Intended as a guide only. Always refer to the manufacturer's recommendations (often printed on a label attached to the battery) before charging a battery. 9 Charge the battery at a rate of 3.5 to 4 amps and continue to charge the battery at this rate until no further rise In specific gravity Is noted over a four hour period. 10 Alternatively, a trickle charger charging at the rate of 1.5 amps can safely be used overnight. 11 Specially rapid boost charges which are claimed to restore the power of the battery in t to 2 hours are not recommended, as they can cause serious damage to the battery plates through overheating, 12 While charging the battery, note that the temperature of the electrolyte should never exceed 37.8*C(100°F),
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501
Chapter 5 PartC:
Preheating system - diesel models
Contents
Glow plugs - removal, inspection and refitting 2 Preheating system - description and testing 1 Preheating system control unit - removal and refitting 3
Degrees of difficulty
Ea3y, suitable
for &
novice with little
|| experience ^
Fairty easy,
suitable for beginner with
some experience
jQ
Fairty diffctit, ^
suitable
for competent
DIY
mechanic
Difficult, suitable for
experienced DIY JR mechanic ^
Very difficult, ^ suitable fbrexpertDfY JR or professional ^
Specifications
Torque wrench setting Nm ibf ft Heater glow plugs 15 11
1 Preheating system -description and testing
Description 1 Each swirl chamber has a heater plug (commonly called a glow plug) screwed into it. The plugs are electrically-operated before and during start-up when the engine is cold. 2 Electrical feed to the glow plugs Is controlled by a relay/timer unit. The coolant temperature determines the period of heating that takes place. 3 A warning light in the instnjment panel tells the driver that preheating is taking place. When the light goes out, the engine is ready to be started. The voltags supply to the glow plugs continues for several seconds after the light goes out, If no attempt is made to start, the timer then cuts off the supply, In order to avoid draining the battery and overheating the glow plugs.
Testing 4 If the system malfunctions, testing is ultimately by substitution of known good units, but some preliminary checks may be made as follows. 5 Connect a voltmeter or 12-volt test lamp between the glow plug supply cable and earth (engine or vehicle metal). Make sure that the live connection is kept clear of the engine and bodywork. 6 Have an assistant switch on the ignition, and check that vottage is applied to the glow plugs. Note the time for which the warning light Is lit. and the total time for which voltage Is applied before the system cuts out. Switch off the ignition. 7 At an under-bonnet temperature of 20°C. typical times noted should be 5 or 6 seconds for warning light operation, followed by a further 10 seconds supply after the light goes out. Warning light time will increase with lower temperatures and decrease with higher temp-eratures.
8 If there Is no supply at all, the relay or associated winng is at fault. 9 To locate a defective glow plug, disconnect the main supply cable and the interconnecting strap from the top of the glow plugs. Be careful not to drop the nuts and washers. 10 Use a continuity tester, or a 12-voH test lamp connected to the battery positive terminal, to check for continuity between each glow plug terminal and earth. The resistance of a glow plug in good condition is very low (less than 1 ohm), so if the test lamp does not light or the continuity tester shows a high resistance, the glow plug is certainly defective. 11 If an ammeter is available, the current draw of each glow plug can be checked. After an initial surge of 15 to 20 amps, each plug should draw approximately 12 amps. Any plug which draws much more or less than this is probably defective. 12 As a final check, the glow plugs can be removed and Inspected as described in the following Section.