thats what i was gonna say too, use a jumper wire on the pressure switch that will eliminate alot of guess work
Help,A/C problem and summer's almost here
Thread Starter
8th Gear
Joined: May 2008
Posts: 8
Likes: 0
A/C clutch not engaging
This 94 is my 1st Corvette,had it almost 2 years. A/C was working . Now my A/C compressor clutch does not engage. Fuse ok. R134 ok.
Thanks in advance,
Thanks in advance,
Last edited by hank88; Jun 6, 2008 at 05:46 PM. Reason: change message
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
There are several things to check and what it could be. I’m assuming the blower fan runs OK.
Check the A/C clutch fuse first, 10 amp.
Check the A/C cycling switch for continuity and to see if connections are not corroded and tight.
Check the A/C clutch relay near inner wheel well passenger side under a bunch of hoses.
Check connector and connectors on PCM.
Check to see if there is any voltage on green wire at the clutch connector.
Although possible, its unlikely the C68 controller is defective. However it can be remotely checked by measuring the resistance on the dark blue wire at the cycling switch when A/C is selected and engine is running. Remove connector and you are looking for continuity to ground which the programmer makes.
Not a good idea to add Freon if the compressor is not turning. The static pressure is probably 90 to 110 lbs (on the low side), where when the compressor is running it is 25 to 45 lb. Your Freon can could probably not push it in there under that higher pressure and could go in reverse.
Check the A/C clutch fuse first, 10 amp.
Check the A/C cycling switch for continuity and to see if connections are not corroded and tight.
Check the A/C clutch relay near inner wheel well passenger side under a bunch of hoses.
Check connector and connectors on PCM.
Check to see if there is any voltage on green wire at the clutch connector.
Although possible, its unlikely the C68 controller is defective. However it can be remotely checked by measuring the resistance on the dark blue wire at the cycling switch when A/C is selected and engine is running. Remove connector and you are looking for continuity to ground which the programmer makes.
Not a good idea to add Freon if the compressor is not turning. The static pressure is probably 90 to 110 lbs (on the low side), where when the compressor is running it is 25 to 45 lb. Your Freon can could probably not push it in there under that higher pressure and could go in reverse.
Last edited by pcolt94; May 23, 2008 at 08:06 AM.
Racer
Joined: Jul 2007
Posts: 313
Likes: 0
From: Laurel MS
Help...This 94 is my 1st Corvette,had it almost 2 years. Now with summer almost here the A/C 's not working. My A/C compressor clutch does not engage. Normally if the system is low on R134 the clutch would click on and off. It did not make any difference when I tried to put in more R134 and gauge showed normal pressure (engine running and A/C switch on). Dashboard shows no warning lights.Anyone knows the problem and if this is a cheap or expensive fix?
From reading the forum there are many helpful knowledgeable owners.
Thanks,
Hank
From reading the forum there are many helpful knowledgeable owners.
Thanks,
Hank
low 22-29psi & high 165-200psi running, factory specs.
Cheers
Check your 6
"You got to know your limitations!", Clint E.
Last edited by jim_hewett; May 23, 2008 at 07:07 AM.
Melting Slicks
Joined: Feb 2005
Posts: 2,135
Likes: 0
From: Sebastian Florida
St. Jude Donor '06
Feel your pain Hank....make a long story short. This A/C stuff is highly specialized & mistakes can be expensive.(like the stock market) Let a professional A/C type look at it! You'll have to define "cheap or expensive" that's relative. Agree 120% regarding the forums invaluable knowledge bank. At best you'll be better educated when your A/C guy debriefs you on the problem. Important..your Denso compressor should read as follows:
low 22-29psi & high 165-200psi running, factory specs.
Cheers
Check your 6
"You got to know your limitations!", Clint E.
low 22-29psi & high 165-200psi running, factory specs.
Cheers
Check your 6
"You got to know your limitations!", Clint E.
There is nothing hard to do on a a/c, you just need the right tools. Get a good set of guages and do as pcolt said and you will be fine.
Also, SUNCR is a great resource for a/c's.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
And if it hasn't thrown a No Gas Code - or some other HVAC Code - go here to see how you retrieve it: https://www.corvetteforum.com/techti...=193&TopicID=2 -
the most likely cause is an intermittent connection at the Low Pressure Switch. You might just disconnect and reconnect the Battery so that any glitches in the Programmer are erased, but your gages show enough static pressure to make it run and assuming the Pressure Signal (that Sensor is on the High Pressure Line and you'll need a scanner to see what it's sending), the compressor should start. So the only thing that can cut power to the the Compressor Relay is the Low Pressure Switch. It takes 50 psi to close the Switch Contacts (and your gages show that), so with the harness unplugged, your DVM should show a closed circuit across the Switch Terminals. Then reconnect the harness and hold it firmly onto the switch - wriggle it around and see if that gets it going. Finally, jumper the harness connector terminals with a paperclip. If any of this gets it running, buy a new connector.
the most likely cause is an intermittent connection at the Low Pressure Switch. You might just disconnect and reconnect the Battery so that any glitches in the Programmer are erased, but your gages show enough static pressure to make it run and assuming the Pressure Signal (that Sensor is on the High Pressure Line and you'll need a scanner to see what it's sending), the compressor should start. So the only thing that can cut power to the the Compressor Relay is the Low Pressure Switch. It takes 50 psi to close the Switch Contacts (and your gages show that), so with the harness unplugged, your DVM should show a closed circuit across the Switch Terminals. Then reconnect the harness and hold it firmly onto the switch - wriggle it around and see if that gets it going. Finally, jumper the harness connector terminals with a paperclip. If any of this gets it running, buy a new connector.
Thread Starter
8th Gear
Joined: May 2008
Posts: 8
Likes: 0
Help.A/C problem and summer's almost here
I'm new at this, sorry for my ignorance. Where's the low pressure switch located. Where does the ends of the paper clip or jumper wire touch?
Your's and "coors2003" tip sounds the easiest to start with.
I'm amazed at everyone's helpfulness.
THANKS!
Your's and "coors2003" tip sounds the easiest to start with.
I'm amazed at everyone's helpfulness.
THANKS!
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Safety Car
Joined: Oct 2007
Posts: 3,816
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From: :45 minutes from everywhere / E-I-E-I-O
In this pic, pull the connector off of the switch on the 12 oclock position of this thing I can't remember what it's called.
In the vette it's the same device, just behind the radiator passenger side.
Jump the wire leads with a paper clip, turn on the A/C, and see if it trips on the compressor.
Get back on that......
In the vette it's the same device, just behind the radiator passenger side.
Jump the wire leads with a paper clip, turn on the A/C, and see if it trips on the compressor.
Get back on that......
Thread Starter
8th Gear
Joined: May 2008
Posts: 8
Likes: 0
help,A/C problem and summer's almost here
Re: low pressure switch.
I pulled out the connector that has 3 wires.( black,tan/purple). The other connector has 1 red wire.
Which contacts and color wires of the 3 do I jump?
By the way ,thanks for the photo,great help.
Hank
I pulled out the connector that has 3 wires.( black,tan/purple). The other connector has 1 red wire.
Which contacts and color wires of the 3 do I jump?
By the way ,thanks for the photo,great help.
Hank
Last edited by hank88; May 28, 2008 at 01:45 PM.
Intermediate
Joined: May 2008
Posts: 38
Likes: 1
From: Yuba City CA
Possible A/C Compressor?
Hi,
I just went through this on my '87. The R-4 compressor has a large 2 or 3 lip seal for the back cover. In my case, the compressor would hold a vacuum but leaked under pressure. If this is the problem, you can use a camero compressor costing much less with a simple pully swap.
You can get a kit for this compressor for around $14.00
I went through several used compressors all with the same problem.
Good luck.
I just went through this on my '87. The R-4 compressor has a large 2 or 3 lip seal for the back cover. In my case, the compressor would hold a vacuum but leaked under pressure. If this is the problem, you can use a camero compressor costing much less with a simple pully swap.
You can get a kit for this compressor for around $14.00
I went through several used compressors all with the same problem.
Good luck.
Safety Car
Joined: Oct 2007
Posts: 3,816
Likes: 0
From: :45 minutes from everywhere / E-I-E-I-O
The paper clip trick will work, but I'm not sure where the low pressure switch is to do the test trick...
Anybody? Where is the low pressure cut-out connector / switch, for him to disconnect and jump it?
I just looked at Haynes, and I don't even see a low pressure cut-out switch...
ed.:Normally if the system is low on R134 the clutch would click on and off. It did not make any difference when I tried to put in more R134 and gauge showed normal pressure (engine running and A/C switch on).
Last edited by schrade; May 28, 2008 at 12:50 AM.
