cooling fans and A/C - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 03-14-2008, 06:28 PM   #1
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well, my AC has never worked. it blows, but not cold air. My cooling fans also never worked. Today, it was decent weather so i decided to mess with the fans. I discovered a few things:
-Unplugging the A/C pressure switch turns them on
-Turning on the AC does not.
-According to my scan tool, the AC compressor is not engaging even when i turn the dial to AC.

Could the AC problem be causing the fan problem?( maybe a faulty pressure switch, etc)
since the fans come on with the pressure sensor pulled, does that mean the fan relay is good?
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Old 03-15-2008, 12:45 AM   #2
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According to the '97 FSM, the PCM does take input from the high pressure side of the A/C system as well as other inputs to determine whether to command the cooling fans on and off. One of the tests (among MANY) in the "Cooling fans not working" is if the high side pressure is too high. If it is, the FSM says to go to the HVAC system diagnosis for repair, so it does appear that too high of pressure in the A/C high side might have an effect on the functioning of the cooling fans, but it is not tiotally spelled out that way in the manual. Not nessesarily directly related to the pressure switch, though.
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Old 03-15-2008, 01:00 AM   #3
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this is for the 95, sorry. may be different since it is OBD-1?
i looked over a chiltons at the library, and it said that the high speed came on when the coolant temp was over 226*, or the AC pressure was over a certain amount. i read it as one or the other, not a combination of the AC pressure and others, but maybe you're right.... if the A/C system needs to be charged, do you think that would affect the fans?
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Old 03-15-2008, 10:54 AM   #4
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It'* either OR.

If your fans came on when the switch was disconnected, the relay is good. You should have no problem doing a fan override.
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Old 03-15-2008, 11:35 AM   #5
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I found this out on my own last year when my fans were on all the time. I found a broken wire from the pressure switch, so by default if the PCM sees high pressure or no signal from the switch it signals fans to be on.
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Old 03-26-2008, 10:32 AM   #6
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Ok, I need to fix my cooling fans also and i'm going to take a lick at them in a minute here. Now, the switch that plugs directly into the A/C Compressor is broke. I have a new unit (hehehe), but never got around to fixing my belt sanded connector. Would this be why my fans may not be coming on? I try to be on top of the jargon on here, but my words are differant. Anyways, should I easy fix and hot wire the fans, or should I follow through and diagnose and fix.
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