Different A/C question
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Instructor
Joined: Oct 2006
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From: Giddings Tx
Different A/C question
Ok, i hope someone has seen this before....my A/C compressor runs all the time, even when the climate control is off??? Please don't tell me the control unit is bad, cause if it is I'll just have too go without A/C. Money's too tight to fix right now especially with school starting back up and having to buy clothes for two kids. Any help would be appriciated.... Thanks Jim
Instructor
Joined: Aug 2007
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Safety Car
Joined: Jul 2004
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....don't think so!
..the compressor shouldn't run without power going to it through the relay...the lp switch is to prevent "freeze-ups" and running with insufficient charge!....while it is true that the lp switch can be shorted to make the compressor turn on, shorting it wouldn't do anything unless there was power going through it first...it can also be intentionally shorted to "draw" refrigerant when recharging system from scratch...
Instructor
Joined: Aug 2007
Posts: 175
Likes: 0
Your car has a Cycling Clutch Orifice Tube (CCOT) refrigeration system designed to cycle a compressor on and off to maintain desired cooling and to prevent evaporator freeze.
Control of the refrigeration cycle (on and off), is done with a switch which senses low side pressure as an indicator of evaporator temp.
This is from my 96 but your's should be similiar. The Hvac programmer sends a request for A/C to the PCM via the press cycling switch by grounding this circuit. This NO switch cycles on and off and must be jumped to refill an empty system. If the switch is closed, the PCM grounds the clutch relay through term 86. The relay then closes providing 12V is avail at 85 and 87 thru the A/C clutch fuse.
The feedback to the PCM via CKT 59 tell the PCM that the clutch is engaged and is used to maintain idle speed.
Disconnect 86 and the clutch should disengage. If it does then check the A/C request circuit for a short. If not. the relay is stuck closed.
Good luck!
Control of the refrigeration cycle (on and off), is done with a switch which senses low side pressure as an indicator of evaporator temp.
This is from my 96 but your's should be similiar. The Hvac programmer sends a request for A/C to the PCM via the press cycling switch by grounding this circuit. This NO switch cycles on and off and must be jumped to refill an empty system. If the switch is closed, the PCM grounds the clutch relay through term 86. The relay then closes providing 12V is avail at 85 and 87 thru the A/C clutch fuse.
The feedback to the PCM via CKT 59 tell the PCM that the clutch is engaged and is used to maintain idle speed.
Disconnect 86 and the clutch should disengage. If it does then check the A/C request circuit for a short. If not. the relay is stuck closed.
Good luck!
Last edited by InHot; Aug 18, 2007 at 12:32 PM.
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