Cool and AC fans not working

Tiny
DALICH
  • MEMBER
  • 1995 BUICK CENTURY
Engine Cooling problem 4 cyl Two Wheel Drive Automatic 140000 miles

I have a 95 Buick Century and the cooling fans will not turn on. Fuses and relays check okay. Additionally, the AC compressor and fans will not operate when I turn the AC on. Are the AC and cooling fans (ac compressor) controlled by and same unit? If so, where is this and how else can I diagnose this. The vehicle it too old for the code scanners.
Do you
have the same problem?
Yes
No
Sunday, October 24th, 2010 AT 11:13 AM

9 Replies

Tiny
DOCFIXIT
  • EXPERT
Hi

PCM controls AC comp and fan relays upon a signal from Heater-AC control head. Does blower fan work on all speeds and does mode select operate? How where relays tested?

Here is a guide to check for power and the wiring diagrams for the air conditioner systems with the pressure switch locations so you can see how to test it.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Let me know
Was this
answer
helpful?
Yes
No
+1
Sunday, October 24th, 2010 AT 3:04 PM
Tiny
DALICH
  • MEMBER
Neither of the front or rear cooling fans cone on when the AC is on (or when hot). The cabin blower motor has all 3 speed settings and seems to blow fine. The AC compressor is not working either.

I tested the cooling fan relay by hooking the battery and heard the "click". I also tested the other two pins to continuity when closed. Worked fine. I also jumped the tow fan wires that the relay would close and the fan started to spin (although my paperclip jumper got hot. Lots of amps there :) Just for kicks I also switched the relay with another and still no fans.

I think everything is pointing to the PCM (ECM? Same thing?) Control module. I was also reading that the relay wires would be "hot" and that the PCM would ground the relay when the fans were to come on. I looked for voltage between both of the relay wires and the chassis, but neither was "hot" and they appear to be an open circuit.

This is my mothers car and a few weeks ago it simply would not start. She had a neighbor help out and ended up replacing the ICM and then received spark. I think there was some experimenting that may have been done in the process that took out the cooling fan portion of the ECM.

Does this sound viable?

Thank you, Dan
Was this
answer
helpful?
Yes
No
-1
Monday, October 25th, 2010 AT 5:59 PM
Tiny
DOCFIXIT
  • EXPERT
At primary fan relay locate Dark Green wire goes to PCM attach test light to batt POS. Probe wire does it light when AC is requested? Do same at AC comp relay Dark green/Wite wire. If no light and fans don't come when engine hot then PCM at fault. Don't know what happened but suspect PCM was back probed with high impedence devise like test light and fried something.
Was this
answer
helpful?
Yes
No
Tuesday, October 26th, 2010 AT 11:42 AM
Tiny
DALICH
  • MEMBER
I'll test as described. I'm fairly sure the PCM is bad here. Last question. Is the ECM and the PCM the same module here? If I am not mistaken the ECM is located under the drivers side dash inside the cab area. Whould this be correct?

Thank you for your help.

Dan
Was this
answer
helpful?
Yes
No
Tuesday, October 26th, 2010 AT 3:07 PM
Tiny
DOCFIXIT
  • EXPERT
Yea PCM looking like the culprit. ECM is old term for OBD1 PCM is OBD11. Located under right side dash next to ABS module.
Was this
answer
helpful?
Yes
No
+1
Tuesday, October 26th, 2010 AT 3:44 PM
Tiny
DALICH
  • MEMBER
Just placed in a new EMC (had to use exisitng eprom). Still no fans. Is there an easy way to hook up the cooling fan relay to run while engine is running? Still no AC or AC fan, but the blower motor in the cab is working on all speeds.

Where is the temp sensor that sends the engine temp to the EMC? Can this be tested? It would not explain why the AC fan is not blowing, but at least it may keep the cooling fan working.

Thanks,
Dan
Was this
answer
helpful?
Yes
No
+1
Sunday, October 31st, 2010 AT 1:32 PM
Tiny
DOCFIXIT
  • EXPERT
On left side steering column find in line fuse taped to harness see if it is good.
Was this
answer
helpful?
Yes
No
Sunday, October 31st, 2010 AT 2:08 PM
Tiny
DALICH
  • MEMBER
I pulled off the bottom side of the dash and I'm looking all over the steering column, but can't seem to find a fuse.

Interesting development. I cut the red wire on the coil of the cooling fan relay and hard wired it to(+). The cooling fan will operate when AC is on AND operate when engine gets hot. How is the "hot" side supplied to the fan relay? At least the cooling fan will operate "normally" with this fix, however that still leaves the question of what happened to the AC.

So I jumpered the low pressure sensor and the system kicked on. It was low on freeon. I wish I checked that earlier.

Thanks for helping me check it out.
Was this
answer
helpful?
Yes
No
+1
Sunday, October 31st, 2010 AT 3:46 PM
Tiny
DOCFIXIT
  • EXPERT
Use 2CarPros anytime, we are here to help. Please tell a friend.

Cheers, Ken
Was this
answer
helpful?
Yes
No
Monday, November 1st, 2010 AT 12:05 PM

Please login or register to post a reply.

Recommended Guides