SERVO-FRONT
DESCRIPTION
The kickdown servo consists of a two-land piston (3)
with an inner piston (2), a piston rod (7) and guide,
and a return spring (4). The dual-land piston uses seal
rings on its outer diameters and an O-ring for the
inner piston.
OPERATION
The application of the piston is accomplished by applying pressure between the two lands of the piston. The pres-
sure acts against the larger lower land to push the piston downward, allowing the piston rod to extend though its
guide against the apply lever. Release of the servo at the 2-3 upshift is accomplished by a combination of spring
and line pressure, acting on the bottom of the larger land of the piston. Thesmallpistonisusedtocushionthe
application of the band by bleeding oil through a small orifice in the larger piston, diesel engine only. The release
timing of the kickdown servo is very important to obtain a smooth but firm shift. The release has to be very quick,
just as the front clutch application is taking place. Otherwise, engine runaway or a shift hesitation will occur. To
accomplish this, the band retains itsholding capacity until the front clutch is applied, giving a small amount of over-
lap between them.
Improper heater hose routing.
Plugged heater hoses or supply and return ports at the cooling system connections.
Plugged heater core.
If proper coolant flow through the cooling system is verified, and heater outlet air temperature is low, a mechanical
problem may exist.
MECHANICAL PROBLEMS
Possible locations or causes of insufficient heat due to mechanical problems are as follows:
Obstructed cowl air intake.
Obstructed heater system outlets.
Blend-air door(s) or actuator(s) not functioning properly.
Faulty blower motor system
Faulty A/C-heater control
TEMPERATURE CONTROL
If the heater outlet air temperature cannot be adjusted with the temperature control on the A/C-heater control, the
following could require service:
Faulty A/C-heater control.
Faulty blend door actuator(s).
Faulty, obstructed or improperly installed blend-air door.
Faulty related wiring harness or connectors.
Improper engine coolant temperature.
SPECIFICATIONS
A/C SYSTEM
Item Description Notes
A/C Compressor Denso 10S17 (3.7L/4.7L/5.7L/8.3L
engines)ND-8 PAG oil
Visteon HS-18 (5.9L engine) VC-46 PAG oil
Freeze–up Control Evaporator Temperature Sensor A/C evaporator mounted
High psi Control A/C pressure transducer A/C discharge line mounted
Refrigerant Charge Capacity Refer to the A/C Underhood
Specification Label located in the
engine compartment.R134a refrigerant
A/C Clutch Field Coil Draw 3.2 - 3.3 amps @ 12V ± 0.5V @
21° C (70° F)3.7L/4.7L/5.7L/8.3L engines
3.1 - 4 amps @ 12V ± 0.5V @ 21°
C(70°F)5.9L engine
A/C Clutch Air Gap 0.35 - 0.60 mm (0.014 - 0.024 in.) 3.7L/4.7L/5.7L/8.3L engines
0.35 - 0.75 mm (0.014 - 0.030 in.) 5.9L engine
TORQUE
OIL-A/C REFRIGERANT
DESCRIPTION
The refrigerant oil used in R-134a refrigerant systems is a synthetic-based, polyalkylene glycol (PAG), wax-free
lubricant. Mineral-based R-12 refrigerant oils are not compatible with PAG oils, and should never be introduced to
an R-134a refrigerant system.
There are different PAG oils available, and each contains a different additive package. Useonlyrefrigerant oil of the
same type as recommended to service the refrigerant system (always refer to the specification tagincluded with
the replacement A/C compressor or the A/C Underhood Specification Label located in the engine compartment).
The Denso 10S17 A/C compressor used in this vehicle when equipped with the 3.7L, 4.7L, 5.7L or 8.3L engine is
designed to use ND-8 PAG refrigerant oil. Use only this type of refrigerantoil when servicing the A/C compressor for
these engines.
The Visteon HS-18 A/C compressor used in this vehicle when equipped with 5.9L diesel engine is designed to use
VC-46 PAG refrigerant oil. Use only this type of refrigerant oil when servicing this A/C compressor.
OPERATION
After performing any refrigerant recovery or recycling operation, always replenish the refrigerant system with the
same amount of the recommended refrigerant oil as was removed. Too little refrigerant oil can cause A/C compres-
sor damage, and too much can reduce A/C system performance.
PAG refrigerant oil is more hygroscopic than mineral oil, and will absorb any moisture it comes into contact with,
even moisture in the air. The PAG oil container should always be kept tightly capped until it is ready to be used.
After use, recap the oil container immediately to prevent moisture contamination.
STANDARD PROCEDURE
REFRIGERANT OIL LEVEL
When an A/C system is assembled at the factory, all components except the A/C compressor are refrigerant oil free.
After the refrigerant system has been charged and operated, the refrigerant oil in the A/C compressor is dispersed
throughout the refrigerant system. The accumulator, A/C evaporator, A/Ccondenser and the A/C compressor will
each retain a significant amount of the needed refrigerant oil.
It is important to have the correct amount of refrigerant oil in the A/C system. This ensures proper lubrication of the
A/C compressor. Too little oil will result in damage to the A/C compressor,while too much oil will reduce the cooling
capacity of the A/C system and consequently result in higher discharge airtemperatures.
CAUTION: The refrigerant oil in the R-134a A/C system is unique depending on the A/C compressor used.
Use only PAG oils that are designed to work with R-134a refrigerant and the A/C compressor in the vehicle.
Always refer to the A/C Underhood Specification Label for the correct oil designation. The oil container
should be kept tightly capped until it is ready for use and then tightly capped after use to prevent contam-
ination from dirt and moisture. Refrigerant oil will quickly absorb any moisture it comes in contact with,
therefore, special effort must be used to keep all R-134a system components moisture-free. Moisture in the
refrigerant oil is very difficult toremove and will cause a reliability problem with the A/C compressor.
NOTE: Most reclaim/recycling equipment will measure the lubricant beingremoved during recovery. This
amount of lubricant should be added back into the system. Refer to the reclaim/recycling equipment man-
ufacturers instructions.
It will not be necessary to check the oil level in the A/C compressor or to addoil, unless there has been an oil loss.
An oil loss may occur due to a rupture or leak from a refrigerant line, a connector fitting, a component, or a com-
ponent seal. If a leak occurs, add 30 milliliters (1 fluid ounce) of refrigerant oil to the refrigerant system after the
repair has been made. Refrigerant oil loss will be evident at the leak pointby the presence of a wet, shiny surface
around the leak.
Refrigerant oil must be added when an accumulator, A/C evaporator or A/C condenser is replaced. See the Refrig-
erant Oil Capacities chart. When an A/C compressor is replaced, the refrigerant oil must be drained from the old