Air conditioning problem
Thread Starter
Racer
Joined: Jun 2002
Posts: 278
Likes: 0
From: Perry Ga
Air conditioning problem
Need help. When I turn on my ac, it is warm and as I drive down the road it gets cold like it should, When the ac is on the engine startes to surge and at stop the engine surge to 8rpm and low as 5rpm. when I cut off the engine and start back up the ac does the same thing all over agian with the engine surging. This problem doen't happen every time but does more than not. Any suggestions would be most helpful.
When I cut the engine off, and start back up and driving down the road the problem starts all over agian.
When I cut the engine off, and start back up and driving down the road the problem starts all over agian.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Sounds like the ECM is not compensating for the a/c signal. Assuming this is the '88 in your Profile, it runs from the Control Panel to Pin B7 at the ECM. With the a/c on, there should be battery voltage (Manual Air) or 6 volts (Electronic Air) on this wire. If the signal is there (If not, it's the Panel or the wire), the ECM is bad - Easier to confirm with a scanner. That will show the request signal as a "Yes" or a "No", the Load Variable should increase, and if it is at a stop, the IAC counts should increase maintaining Targeted Idle.
Instructor
Joined: Mar 2007
Posts: 194
Likes: 10
From: King George Virginia
I suggest you check the simple things first. Have the charge checked. A low charge will cause cycling, which in turn can produce the symptoms you describe. An easy quick way is to watch the clutch on the compressor, A/C on high on a moderately warm day it should not be cycling on and off. I'm not saying it can't be the ECM, but just out of the winter season we see these problems all the time and the vast majority of the time it's just a low charge.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Hate to disagree, but not with 300 rpm difference at idle - the controls weren't that lame! Of course that's not to say that the compressor isn't shot, but most - and if there was a low charge - don't make cold air. Some a/c shops do have scanners and if you don't, an honest one should be able to sort it out.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
idle
1. My car has a bad brake booster on it right now, and it does the same thing. Idle surges when cold, when in closed loop, the IAC compensates for it.
The warm air at first is the loss of vacuum until the engine can fill the ball with vacuum, and pull off the heater valve.
Open the hood, get someone to start your car, and watch the heater valve. Suddenly, the vacuum solenoid pulls the valve shut, and then the air starts to cool inside the car.
The warm air at first is the loss of vacuum until the engine can fill the ball with vacuum, and pull off the heater valve.
Open the hood, get someone to start your car, and watch the heater valve. Suddenly, the vacuum solenoid pulls the valve shut, and then the air starts to cool inside the car.
Thread Starter
Racer
Joined: Jun 2002
Posts: 278
Likes: 0
From: Perry Ga
I kinda wondered if the ecm has gone south. The gas range doesnt seem to calculate properly and the average is acting strangly. Any way I had the a/c system converted last year and recharged. The car isn't my daily driver, so I was thinking low on freon. I know a good friend in the mechanic business, I think I will take it to him to put a scan on the ecm.
Thanks for the inputs
Thanks for the inputs
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
1. My car has a bad brake booster on it right now, and it does the same thing. Idle surges when cold, when in closed loop, the IAC compensates for it.
The warm air at first is the loss of vacuum until the engine can fill the ball with vacuum, and pull off the heater valve.
Open the hood, get someone to start your car, and watch the heater valve. Suddenly, the vacuum solenoid pulls the valve shut, and then the air starts to cool inside the car.
The warm air at first is the loss of vacuum until the engine can fill the ball with vacuum, and pull off the heater valve.
Open the hood, get someone to start your car, and watch the heater valve. Suddenly, the vacuum solenoid pulls the valve shut, and then the air starts to cool inside the car.
Vacuum has nothing to do with the Temp Door. Do you mean the heater hose control valve? As far as I know, it isn't used on this Year. If you mean the Temp Door, it's mechanically controlled - either by an electric motor (electronic air) or a cable (manual). If the Door is cycling (electronic air) and the controls display 75 when you start it, that's a sign that its losing memory power when you turn off the key. Check ground, Driver's side kick panel. Also, Electronic air, by default, blows for a few seconds out of the heater ducts when you start it to keep the windshield from fogging over. Then the a/c setting directs the majority air out of the vents, with a tad out of the defroster, heat vents (to cool the floor) and door vents if equipped.
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