1997 Cadillac Deville fan heater A/C

GERALD LEGG

MEMBER
1997 CADILLAC DEVILLE
V8
FWD
AUTOMATIC
88,791 MILES

The fan for the heater and a/c only comes on occasionly for example in the morning when I need defroster the fan will not come on but in the after noon when its warmer it will come on if I left it on when I shut the car off. Or somtines the air conditioner will blow if I left it on when I shut the car off, but not lately

I have ran the self diagnostics for ACM I did not get any trouble codes and no flash on outside tempeture (it stayed on) I look at connections to sensor behind front grill and solar radiation sensor under defrost vent and both have good conections. What should I do now?

1 Reply

MERLIN2021

MECHANIC
17,250 POSTS

Run this test and post all codes that come up.
A/C-HEATER SYSTEM - AUTOMATIC -1997 Cadillac DeVille
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NOTE: Operating vehicle in self-diagnostic mode for extended period without engine running will drain battery, possibly causing system to give false diagnostic information. If vehicle is in self-diagnostic mode for more than 30 minutes, connect charger to battery.

ACM SELF-DIAGNOSTICS
Fault Detection
If ACM detects a system fault, the Vacuum Fluorescent (VF) display on the climate control panel will flash one time per second for 100 seconds. If a fault occurs in the outside temperature sensor circuit, VF display will not flash, but the outside temperature will not be displayed.
NOTE: ACM and Climate Control Panel (CCP) store self-diagnostic trouble codes used to identify source of any system malfunction. Diagnostic Trouble Codes (DTCs) are designed to identify malfunction as specifically as possible, including type of DTC (current or non-current history).
NOTE: Self-diagnostics only allows viewing and clearing of DTCs. Testing and overriding A/C system operations can only be accomplished using a scan tool.

Entering Self-Diagnostics (With Climate Control Center)
Turn ignition switch to ON position. Press OFF button and WARMER button (standard A/C-heater system), or OFF button and PASSENGER WARMER button (dual zone A/C-heater system). See Fig. 1 or Fig. 2. Press LO fan speed (down arrow) button until ACM? Is displayed. Press HI fan speed (up arrow) and ACM CODES? Is displayed. Press HI fan speed (up arrow), DTCs are displayed. See DIAGNOSTIC TROUBLE CODES.
Entering Self-Diagnostics (With Scan Tool)
Connect scan tool to DLC connector located under instrument panel, on hood release bracket. Select ACM. Select DTC. Select CURRENT DTC for current DTCs or HISTORY DTC for history DTCs.

Clearing DTCs (With Climate Control Center)
Enter self-diagnostics. Press OFF button and WARMER button (standard A/C-heater system), or OFF button and PASSENGER WARMER button (dual zone A/C-heater system). Press fan LO speed (down arrow) until ACM is displayed. Press fan HI (up arrow) until ACM CODES? Is displayed. Press fan LO (down arrow) until ACM CLEAR CODES? Is displayed. To clear DTCs, press fan HI (up arrow) until ACM CODES CLEAR is displayed.