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My AC doesn't want to blow cool or hot air. It was happening slowly for couple of weeks now, and yesterday, no more cool air! The symptom: air blows out of ducts, but it is not cooled at all, and when I put on the heater it is not heated at all. But it blows alright. Think: you get same air as when in VENT mode, no matter if it is in AC or heater mode.

I've replaced AC compressor, orifice tube, and freon R134A, not so long ago. And under warranty I had the guys check it out. The guy said it is something electrical. Both freon and dryer seem alright. He said computer doesn't want to turn on AC, and "this happens when car needs tune-up." Now, I did tune up one year ago. In fact, my whole car is one major tune up, I mod it all the time.

The guy wanted $125 to fix this electrical problem. I figured it has to be something simple, like a fuse or something. Can you help me nail this problem down so I can fix it? I still have time before it gets really hot here, I can drive with my windows down, no problem. Please help.



Fernado
 

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Welcome to the forums!

It's possible there's an electrical problem. I'm not a HVAC technician, so my assistance is limited to posting diagnostics routines. Here's the diagnostics routine from the 1994 Service Manual:

PINPOINT TEST D: A/C DOES NOT OPERATE

D1 CHECK COMPRESSOR CLUTCH
Prepare vehicle as follows:
Connect manifold gauge.
Set function control at MAX A/C.
Set blower switch on HIGH.
Set temperature lever full cold.
Close doors and windows.
Run engine at approximately 1500 rpm.
Does A/C clutch operate?
Yes
GO to D11.

No
GO to D2.


D2 CHECK VOLTAGE SUPPLY AT SWITCH
Turn engine off. Leave ignition switch ON.
Using a test lamp, check for voltage at Pin 2 Circuit 296 (W/P) at A/C heater control switch.
Did test lamp illuminate?
Yes
GO to D5.

No
GO to D3.


D3 CHECK VOLTAGE SUPPLY TO SWITCH
Using a test lamp, check voltage at output side of Fuse 6 (15A).
Did test lamp illuminate?
Yes
SERVICE Circuit 296 (W/P) for open circuit. RESTORE vehicle. RETEST system.

No
GO to D4.


D4 CHECK CIRCUIT 296 (W/P) FOR SHORT
Using an ohmmeter, connect one lead to output side of Fuse 6 (15A). Connect second lead to a known good ground.
Disconnect A/C heater control switch.
Is resistance 5 ohms or less?
Yes
SERVICE Circuit 296 (W/P) for short to ground. REPLACE Fuse 6 (15A). RESTORE vehicle. RETEST system.

No
GO to D5.


D5 CHECK A/C, HEATER CONTROL SWITCH
Reconnect A/C, heater control switch.
Using a test lamp, check voltage at Pin 4 Circuit 348 (P).
Did test lamp illuminate?
Yes
GO to D6.

No
REPLACE A/C, heater control switch. RESTORE vehicle. RETEST system.


D6 CHECK CLUTCH CYCLING PRESSURE SWITCH
Disconnect clutch cycling switch.
Start engine, A/C should be in MAX A/C mode.
Using a jumper wire, connect one end to Pin 1 at cycling switch connector. Connect second lead to Pin 2 at cycling switch.
Observe A/C clutch .
Did A/C clutch engage?
Yes
REPLACE A/C cyclic switch . Do not discharge system. Switch has a Schrader valve. RESTORE vehicle. RETEST system.

No
GO to D7.


D7 CHECK A/C INPUT TO CONSTANT CONTROLLED RELAY MODULE (CCRM)
NOTE: Refer to CCRM circuits and connector views for terminal pin identification.

Turn engine off, leave ignition switch ON. Gain access to (CCRM) as outlined.
Using test lamp check Pin 21 Circuit 198 (DG/O) at (CCRM) connector for voltage.
Did test lamp illuminate?
Yes
GO to D8.

No
SERVICE Circuit 198 (DG/O) for open circuit. RESTORE vehicle. RETEST system.


D8 CHECK (CCRM) CLUTCH OUTPUT
Using test lamp, check Pin 23 Circuit 347 (BK/Y) for voltage.
Did test lamp illuminate?
Yes
GO to D9.

No
REPLACE constant controlled relay module. RESTORE vehicle. RETEST system.


D9 CHECK SUPPLY TO A/C CLUTCH
Disconnect A/C clutch .
Using a test lamp, check Circuit 347 (BK/Y) at A/C clutch connector.
Did test lamp illuminate?
Yes
GO to D10.

No
SERVICE Circuit 347 (BK/Y) for open circuit.


D10 CHECK A/C CLUTCH GROUND CIRCUIT
Using an ohmmeter, connected to ground, connect second lead to Circuit 57 (BK) at A/C clutch connector.
Measure resistance.
Is resistance 5 ohms or less?
Yes
REPLACE A/C clutch as outlined. RESTORE vehicle. RETEST system.

No
SERVICE Circuit 57 (BK) for open circuit. RESTORE vehicle. RETEST system.


D11 CHECK A/C CLUTCH CYCLING
Use refrigerant system pressure/clutch cycle rate and timing evaluation charts.
After preparing vehicle as follows:
Hook up manifold gauge set.
Set function control at MAX A/C.
Set blower switch on HIGH.
Set temperature lever full COLD.
Close doors and windows.
Use a thermometer to check temperature at center discharge register, record outside temperature.
Run engine at approximately 1500 rpm with compressor clutch engaged.
Stabilize with above conditions for 10-15 minutes.
Check A/C clutch on/off time with watch. Refer to charts for normal clutch cycle timing rates.
Did A/C compressor cycle very rapidly?
Yes
GO to D12.

No
GO to D13.


D12 CHECK CLUTCH CYCLING SWITCH
Using a jumper wire, bypass A/C cyclic switch .
Hand feel A/C evaporator inlet and outlet tubes.
Is outlet tube approximately same temperature -2° C, -4°C (28°F, 40°F) or slightly colder than inlet tube?
Yes
REPLACE A/C cyclic switch . Do not discharge system. Switch has a schrader valve. RESTORE vehicle. RETEST system.

No
DISCHARGE system and SERVICE as outlined. RETEST system.


D13 CHECK A/C SWITCH OUTPUT
Turn ignition switch to the RUN position.
Turn A/C, heater control to the OFF position.
Using a test lamp, check for voltage at Pin 4 Circuit 348 (P) at A/C, heater switch connector.
Did test lamp illuminate?
Yes
REPLACE A/C, heater switch. RESTORE vehicle. RETEST system.

No
GO to D14.


D14 CHECK FOR VOLTAGE TO A/C CLUTCH
Using a test lamp, check Circuit 347 (BK/Y) for voltage.
Did test lamp illuminate?
Yes
REPLACE constant control relay module. RESTORE vehicle. RETEST system.

No
Condition does not exist at this time. RETEST system.
 
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