1990 C4 Base Model A/C not working
Thread Starter
Instructor
Joined: Jul 2020
Posts: 193
Likes: 13
From: Houston Texas
1990 C4 Base Model A/C not working
1990 C4 Base Model A/C not working. All of a sudden, my A/C stopped working. From cold to A/C clutch not turning. I took the negative battery cable off to reset the A/C. Nope, did not work. I put my gage on, and the needle showing charge went to mid red.
So, what should I try next? I changed out the o=rings about 2 years ago, and everything was wonderful for all of this time. What additional testing should I do to get to a fix? Thanks
So, what should I try next? I changed out the o=rings about 2 years ago, and everything was wonderful for all of this time. What additional testing should I do to get to a fix? Thanks
Melting Slicks
Joined: Feb 2003
Posts: 2,672
Likes: 810
From: Saskatoon Sask.
1990 C4 Base Model A/C not working. All of a sudden, my A/C stopped working. From cold to A/C clutch not turning. I took the negative battery cable off to reset the A/C. Nope, did not work. I put my gage on, and the needle showing charge went to mid red.
So, what should I try next? I changed out the o=rings about 2 years ago, and everything was wonderful for all of this time. What additional testing should I do to get to a fix? Thanks
So, what should I try next? I changed out the o=rings about 2 years ago, and everything was wonderful for all of this time. What additional testing should I do to get to a fix? Thanks
Thread Starter
Instructor
Joined: Jul 2020
Posts: 193
Likes: 13
From: Houston Texas
That was the first thing I did. The system did not take any freon. I put the dye in, then tried to get the compressor to activate by adding freon. I did not get a response from the compressor, so I took #2 fuse out to reset the system, still , no response from the compressor. I then removed the negative cable from the battery and let stand for about 15 minutes, then reconnected the cable to the battery. No response from the compressor.
While reading about this in the Service Manual, the Service Manual connected the power connector to the radio to this issue. Last week, I removed my Pioneer stereo to send it back for service.
Question: Might the removal of my stereo trigger this issue? The Service Manual comments about removing the power connector, I think disabling the A/C system. Is this true, or am I reading too much into the comment about the radio power connector?
Le Mans Master
Joined: Sep 2009
Posts: 6,332
Likes: 1,141
From: Vermilion OH
If the system deterct too high of a pressure, the high pressure switch will stop the compressor from cycling to prevent damage. You may also want to apply source voltage to the compressor connector with the engine off to see if the a.c. clutch engages and disengages when voltage is taken away. If the clutch does not engage, it has failed.
Melting Slicks
Joined: Feb 2003
Posts: 2,672
Likes: 810
From: Saskatoon Sask.
If the system deterct too high of a pressure, the high pressure switch will stop the compressor from cycling to prevent damage. You may also want to apply source voltage to the compressor connector with the engine off to see if the a.c. clutch engages and disengages when voltage is taken away. If the clutch does not engage, it has failed.
Drifting
Joined: Jun 2013
Posts: 1,961
Likes: 342
From: Shell Point (Crawfordville) Florida
Where and how are you measuring the pressure in your AC system? You can not measure pressure in your AC system without the compressor running - you are measuring a static pressure which is useless. You probably have low pressure in the system and it is now working as designed, shutting off the compressor to prevent damage to it. If your compressor is not running, you cannot add Freon into the system, and you have to bypass the low pressure switch to get it to turn on, then you can add Freon.
Did you pull the code, is a blinking green light showing up on your AC control panel?
Do a search on here on how to bypass the low pressure switch (and where it is). You also have to reset the 09 code if you have it by disconnecting the battery for 15-30 sec or so before the compressor will turn on.
Did you pull the code, is a blinking green light showing up on your AC control panel?
Do a search on here on how to bypass the low pressure switch (and where it is). You also have to reset the 09 code if you have it by disconnecting the battery for 15-30 sec or so before the compressor will turn on.
Melting Slicks
Joined: Feb 2003
Posts: 2,672
Likes: 810
From: Saskatoon Sask.
Where and how are you measuring the pressure in your AC system? You can not measure pressure in your AC system without the compressor running - you are measuring a static pressure which is useless. You probably have low pressure in the system and it is now working as designed, shutting off the compressor to prevent damage to it. If your compressor is not running, you cannot add Freon into the system, and you have to bypass the low pressure switch to get it to turn on, then you can add Freon.
Did you pull the code, is a blinking green light showing up on your AC control panel?
Do a search on here on how to bypass the low pressure switch (and where it is). You also have to reset the 09 code if you have it by disconnecting the battery for 15-30 sec or so before the compressor will turn on.
Did you pull the code, is a blinking green light showing up on your AC control panel?
Do a search on here on how to bypass the low pressure switch (and where it is). You also have to reset the 09 code if you have it by disconnecting the battery for 15-30 sec or so before the compressor will turn on.
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Drifting
Joined: Jun 2013
Posts: 1,961
Likes: 342
From: Shell Point (Crawfordville) Florida
You are mostly correct but for one thing. The low pressure switch does not shut off the compressor to protect against damage. It shuts off to stop the evaporator from becoming ice bound. Once the pressure drops below~28 PSI, the temperature goes below 32°. So long as the compressor has oil, it doesn't care if it is pumping anything. No different than an engine. If you had a starter that would not burn up, you could crank it till the cows come home and so long as it built oil pressure, no problem.
This from the net as well as AI - Low pressure just above shutoff will cause compressor overheating and shutdown on thermal cutout or seizing from insufficient oil return - no lubrication.
So without getting into an argument, both answers are right, for two different reasons.
And as an aside, if the Freon level happens to be OK, the other reason his compressor doesn't run could be a rare failed low pressure switch, easy to test for.
Melting Slicks
Joined: Feb 2003
Posts: 2,672
Likes: 810
From: Saskatoon Sask.
You are also mostly right. The compressor will shut off to prevent the evaporator from icing up but will also shut off because of insufficient or low oil lubrication due to low coolant (Freon) levels.
This from the net as well as AI - Low pressure just above shutoff will cause compressor overheating and shutdown on thermal cutout or seizing from insufficient oil return - no lubrication.
So without getting into an argument, both answers are right, for two different reasons.
And as an aside, if the Freon level happens to be OK, the other reason his compressor doesn't run could be a rare failed low pressure switch, easy to test for.
This from the net as well as AI - Low pressure just above shutoff will cause compressor overheating and shutdown on thermal cutout or seizing from insufficient oil return - no lubrication.
So without getting into an argument, both answers are right, for two different reasons.
And as an aside, if the Freon level happens to be OK, the other reason his compressor doesn't run could be a rare failed low pressure switch, easy to test for.
Drifting
Joined: Jun 2013
Posts: 1,961
Likes: 342
From: Shell Point (Crawfordville) Florida
It's as valid a statement as yours. "So long as the compressor has oil" - where does that oil come from? If the system pressure is too low, there is insufficient coolant (Freon) and its contained oil circulating, so the compressor can heat up and be damaged, both from low oil as well as the cooling property of the liquid flowing through it. The low pressure switch turns off the compressor to avoid it being damaged as well as the evaporator freezing up. Do you disagree with that? Personally I would think it is more important to save the compressor from damage than to prevent some ice forming on the evaporator.
To the OP - if the system would not take any Freon, how did you put dye in? You need the compressor to run to put anything into the system unless you have the proper high pressure AC equipment to do that.
Unless you try to bypass the low pressure switch by removing the electrical connector and shorting out the switch with a short piece of wire to get the compressor to turn on, you will never add anything to the system and you are wasting your time with other measures which will not help you at all.
Do a little more research on here,
or do yourself a favor and take it to an AC repair shop.
To the OP - if the system would not take any Freon, how did you put dye in? You need the compressor to run to put anything into the system unless you have the proper high pressure AC equipment to do that.
Unless you try to bypass the low pressure switch by removing the electrical connector and shorting out the switch with a short piece of wire to get the compressor to turn on, you will never add anything to the system and you are wasting your time with other measures which will not help you at all.
Do a little more research on here,
or do yourself a favor and take it to an AC repair shop.
Last edited by mrlmd; Today at 02:57 PM.