Insufficient Heat Diagnosis - GMC G Service Manual

INSUFFICIENT HEAT DIAGNOSIS

POSITION THE C O N TRO LS SO THAT THE: TEM PERATU RE LEVER IS ON FULL HEAT.
SELEC TO R OR HEATER LEVER IS ON HEATER. FAN SW ITCH IS ON "HI".
NO AIR FLOW
CHECK THE D EFR O STER O UTLETS FOR AIR FLOW.
(IF IN DOUBT AS TO HIGH O R LOW AIR FLOW, SE T THE SELEC TO R ON
'DEF" W HICH IS HIGH AND COMPARE. R ESET THE SELEC TO R ON HEATER '
NO OR LO W AIR FLOW
CHECK THE HEATER O U TLET A IR FLOW.
(IF IN DOUBT, SWITCH FAN SW ITCH FROM HI TO LO.)
CHANGE IN AIR FLOW
NORMAL MR FLOW
CHECK THE HEATER O U TLET TEM PERA TU RE
WITH A 104°C (220°F) RANGE THERM OM ETER.
(APPROXIMATE O U TLET AIR TEMPERATURES.)
O UTLET AIR 63°C
(145°F)
AM BIENT AIR -18°C
(0°F)
NORMAL TEM PERA TU RE
REMOVE ALL O BSTRUC TIONS FROM
UNDER THE FRO N T SEAT.
IF THE VEHICLE DOES NOT BUILD
UP HEAT- O PERATE THE VE N T C ONTROLS
AND SEE IF THE AIR VE N T DOORS CLOSE
COMPLETELY; IF NOT, ADJUST.
CHECK DUMP DOOR O U TLET FOR AIR FLOW.
68°C 74°C
66°C
(150°F) (155°F) (165°F)
-4°C 4°C 246C
(25°F) (40°F) (75°F)
LOW TEM PERA TU RE
SEE CHART "A "
Figure 1 — Insufficient Heat Diagnosis
ADJUST THE DUMP DOOR
FOR NO AIR FLOW.
HIGH AIR FLOW
ADJUST THE DEFRO STER DOOR
FOR LOW AIR FLOW.
LITTLE O R NO CHANGE IN AIR FLOW
LOW O R NO AIR FLOW
CHECK THE SHUT OFF DOOR POSITION
FOR FULL SYSTEM AIR FLOW.
ADJUST IF NECESSARY.
LOW AIR FLOW
CHECK THE HEATER O UTLET
FOR OBSTRUCTION - REMOVE.
CHECK THE MOTOR VO LTAG E AT
THE CONNECTION C LO SEST THE
M OTOR WITH A VOLTM ETER.
UNDER 10 VO LTS
I
CHECK THE BATTERY VO LTAG E - UNDER 10 VOLTS,
RECHARGE; THEN RECHECK MOTOR VOLTAGE.
-------- I
CHECK THE W IR ING AND CO NNEC TIO NS FOR
UNDER 10 VO LTS FROM THE M OTOR TO THE
FAN SWITCH. REPAIR O R REPLACE LAST
POINT OF UNDER A 10 VO LT READING.
A PPLY EXTER NA L GROUND, (JUMPER W IRE) TO THE
M OTOR CASE. INCREASED AIR FLOW - REPAIR GROUND.
SAME AIR FLOW - R EM O VE THE M O TO R AND
CHECK FOR OBSTRUCTION IN SYSTEM OPENING.
IF NONE, REPLACE MOTOR. IF OBSTRUCTED,
REM O VE THE M ATERIAL AND R EINSTALL MOTOR.
HEATING 1A-3
AIR FLOW
I
NO AIR FLOW
I "
CHECK FUSE
SEE CHART "B"
O VER 10 VO LTS
L00175