1998 HONDA CIVIC cool

Troubleshooting -'96 - 98 Models
Symptom Chart
NOTE;
. Check the engine coolant level. and allow the engine to warm up before troubleshooting.
. Any abnormality must be corrected before continuing the test.
. Because of the precise measurements needed. use a multimeter when testing.
o Before performing any troubleshooting procedures check:- Fuses No. 41 11.5 Al, No. 55 (40 A) in the under-hood fuse/relay box. and No. 17 (7.5 A) in the under-dash fuse/relay
box- Grounds No. G401, G402- Cleanliness and tightness of all connectors
SymptomRomedy
Hot air flow is low.Blower motor runs. but one or more
speeds are inoperative.
Perform the procedures in the flowchart (see page 21-8).
Blower runs properly.Check for the following:. Clogged heater duct. Clogged heater outlet. Incorrect door position
No hot air flow.Blower motor does not run at all,Perform the procedures in the flowchart (see page 21-10).
Blower motor runs.Check for the following:. Clogged heater duct. Clogged blower outlet. Clogged heater valve. Faultv air mix door. Heater valve cable adjustment (see page 21-44). Air mix control cable adiustment (see page 2'l-441. Faulty cooling system thermostat (see section 10). Clogged evaporator (with air conditioning). Frozen evaporator {with air conditioning)
Mode control motor does not run, or one or more modes
are inooerative.
Perform the procedures in the flowchart (see page 21-13).
Recirculation control door does not chanqe between
FRESH and RECIRCULATE.
Perform the procedu.es in the flowchan (see page 21-16).
Both heater and A,/C do not work.Perform the procedures in the flowchart (see page 21-18),
21-6

Troubleshooting -'99 - 00 Models
Symptom
Mode control motor does not run, or one or more modes are inoperat've'
Recirculation control door does not change between Fresh and Recirculate'
Blower motor only runs on high speed position; it does not run in any other speed positions
Blower motor does not run at all.
Both heater and Ay'C do not work
See pags
a1_tq
21-21
21-29
21-31
21 35
Symptom Chart
For electrical malfunctions which are indicated by the self-diagnostic system, refer to self-diagnosis function (see next
page).
Note these items before troubleshooting a symptom'
. Check the engine coolant level, and allow the engine to warm up before troubleshooting'
. Any abnormality must be corrected before continuing the test
.Becauseoftheprec|semeasurementsneeded,UseadigitaImu|timeterwithanoutputoflmAor|essatthe20ko
range when testing
. Before performing any troubleshooting procedures check:
- Fuses No. 41 115 Al, No 55 (40 A)]n the under-hood fuse/relay box' and No 17 (7 5 A) in the under-dash fuse/relav
box- Grounds No. G401, G402
- Cleanliness and tightness of all connectors
21-19

Air Mix Gontrol Motor
Recirculation indicator light indicates Diagnostic Trouble code (DTC) 1l A problem in the air mix control linkage, door and
motor.
The air mix control motor regulates the mixture of cool/hot air according to outputs from the heater control panel'
Self-diagnosis circuit check indi'
cates a Problem in the air mix
conlrol motor circuit,
Check th6 aii mix conirol motor:
1. Disconnect the air mix control
motor 5P connector.
2. Test the air mix control motor(see page 21-46).
check the air mix control linkage
and doors:1. Remove the air mix control
motor (see Page 21-46)
2. Check the air mix control link-
age and doors lor smooth
movement.
ls the air mix control motor OK?
Do the air mix control linkage and
doors move smoolhlY?
R€olace the air mix control motor'
Check tor a short in the wiles:
1. Disconnect the heater controlpanel 20P connector-2. Check for continuitY between
body ground and the heater
control panel 20P connector
terminals No.3 and 4 individ'
uaIY.
Ropair any short in th€ wire{s}
betweon the heater control Paneland the air mix control motor'
HEATER CONTROL PANEL 2OP CONNECTOR
RED/WHTRED/YEL
Wire side ot female terminals
(cont'd)
fo page 21-22
21-21

RecirculationindicatorIightindicatesDiagnosticTroublecode(DTc)2:AprobIemintheairmixcontro|motorcircuit.
The air mix control motor regutates the mi)dure of cool/hot air according to outputs from the heater control panel'
Self-diagnosis circuit check indi-
crl6s a problgm in tho air mix
contiol motor circuit.
Check th6 rir mix control motor:
1. Disconnect the air mix control
motor 5P connector'
2. Test the air mix control motor(see page 21-46).
Check the air mix control linkage
and doors:1. Remove the air mix control
motor (see page 21'46).
2. Check the air mix control link-
age and doors for smooth
ls the air mix control motor OK?
Do the air mix control linkage and
doors move smoothlY?
Roglace the air mix conlrol motor.
Check for r short in the wiresl
1. Disconnect the heater controlpanel 20P connector.2. Check for continuity between
body ground and the heater
control panel 20P connector
terminafs No. 3,4. 12,15 a^d
20 individually
Bep.ir any short in the wire{s)
between the h€rter control panel
and th6 air mix control motor.ls there continuity?
HEATER CONTROL PANEL 2OP CONNECTOR
BEO/WHTREO/YEL
PNK/BLK
Wire side of female terminals
(cont'd)
Io page 21-24
21-23

Troubleshooting -'99 - 00 Models
Heater Control Panel Input/Output Signals
HEATER CONTROL PANEL CONNECTORS
8P CONNECTOR2OP CONNECTOR12P CONNECTOR
Wire side of female terminals
8P CONNECTOR (O qn Circuit Diagram)
20P CONNECTOR {D on circuit Diagram}
*: with Ay'c
12P CONNECTOR (tr on Circuit Diagraml
CavityWire colorSignalCavilyWhe colorSignal
BLU/8LKBLOWER FEEDBACKINPUT5REDDASH LIGHTS BRIGHTNESSCONTROLLEROUTPUT
2GRN/lVHTFRESHINPUT6BLKGBOU N DOUTPUT
3GRN/REDRECIRCULATEINPUT7BLU/YELREAR WINDOW DEFOGGERRELAYOUTPUT
4RED/BLKCOMBINATION LIGHT SWITCH(Via No. 30 (7.5 A) fuse)INPUT88LfiELlG2 {Power)INPUT
CavityWire colorSignalCavityWire colorSignal
LTGRN/BLKPOWER TRANSISTOR EASEOUTPUT't1BLU/REDAy'C THERMOSTATINPUT
2BRNMHTMODE CONTROL MOTORGROUNDINPUT12BRNAIR MIX CONTROL MOTORGROU NDINPUT
3RE D/YELAIR MIX HOTOUTPUT13ORNAA/HTBLOWER MOTOR HIGHRELAYINPUT
RED,ryvHIAIR MIX COOLOUTPUT14
5YEUBLUMODE DEFINPUTPN K,/BLKAIR MIX POTENTIALOUTPUT
6YEUREDMODE VENTINPUT16
7GRNI/ELMODE HEAT/r'ENTINPUT11
IBLUAVHTMODE HEATINPUT18
9YELMODE HEAT/DEFINPUT19
10WHT/BLU+B (Power)INPUT20GRYAIR MIX POTENTIAL +5 VOUTPUT
CavityWilecolorSignalCavityWi.e cololSignal
lSWITCH LED COMMONOUTPUT1SWITCH LIGHTS +OUTPUT
2ISWITCH LIGHTS -INPUT
39SWITCH COMMONINPUT
4RECIRCULATION CONTROLSWITCH LEDINPUT10A,/C SWITCHOUTPUT
5A./C SWITCH LEDINPUT11RECIRCULATION CONTROLSWITCHOUTPUT
6REAR WINDOW DEFOGGERSWITCH LEDINPUT12REAR WINDOW DEFOGGEBSWITCHOUTPUT
21-36

Heater Unit
Replacement
SRS components are located in this area. Review the
SRS component locations, precautions, and procedures
in the SRS section {24} before performing repairs or ser-
L Disconnect the negative cable from the battery.
2. Frcm under the hood, open the clamp, then discon-
nect the heater valve cable from the heater valve
arm. Turn the heater valve arm to the fully opened
position as shown.
When the engine is cool. drain the engine coolant
from the radiator (see section 10).
!@ Do not remove the radiator cap when
the engine is hot; the ongine coolant is under pres'
surg and could severely scald you.
CLAMP
HEATER VALVC CABLE
4. Disconnect the heater hoses from the heater unit.
CAUTION: Engine coolant will damage p8int.
Ouickly rinse any spilled engins coolant from painted
su aces,
NOTE: Engine coolant will run out when the hoses
are disconnected; drain it into a clean drip pan.
5. Remove the mounting nut from the heater unit.
NOTE: When removing the mounting nut, take care
not to damage or bend the fuel lines, the brake
lines, etc.
I x 1 .25 mm22 N.m {2.2 kgl.m, 16lblftl
21-39

Heater Unit
Replacement (cont'dl
6.
7.
8.
9.
Remove the dashboard (see section 20).
Remove the heater duct (see page 21-37) or evapo-
rator (see page 22-28).
Disconnect the connectors from the mode control
motor and air mix control motor ('99 - 00 models),
then remove the wire harness clips and wire har-
ness from the heater unit. Remove the clip from the
heater duct, then remove the two mounting nuts
and the heater unit.
6x1.0mm9.8 N.m 11.0 kgl.m,7.2 lbf.ftl
HEATER UNIT
lnstall in the reverse order of removal. Make note of
the following items.
Apply sealant to the grommets.
Do not interchange the inlet and outlet heater
hoses. Make sure that the clamps are secure.
Refill the cooling system with engine coolant
(see section 10).
Connect all cables, and make sure they are prop-
erly adjusted (see page 21-44 (96 - 98 models)
or page 21-45 ('99 - 00 models)).
Make sure that there is no air leakage.
21-40

Temperature Control
Adjustment -'96 - 98 Models
1. From under the hood, disconnect the heater valve
cable from the heater valve.
TERVALVECABLEHEATER VALVE ARM
2.From under the dash, disconnect the air mix control
cable housing from the cable clamp,
AIR MIXCONTROLARM
3.Set the temperature control lever to MAX. COOL.
With the air mix control cable attached to the air
mix control arm, gently pull on the outer cable
housing to fully close the door and to remove any
slack in the cable. Don't pullto hard, or the temper-
ature control lever will move.
Hold the air mix control arm against the stop. then
snap the air mix control cable housing into the
cable clamp.
21-44
6. From under the hood. move the heater valve arm to
the fully closed position. then attach the heater
valve cable to the heater valve arm.
7. Hold the heater valve arm in the closed position,
and gently pull on the heater cable outer housing to
take up any slack. then install the heater valve cable
housing into the cable clamp.
HEATER VALVE ARM