unknown a/c problem
Thread Starter
Instructor
Joined: Apr 2009
Posts: 118
Likes: 1
From: baltimore md
unknown a/c problem
hi again. my 87 vert has an a/c issue, a mystery. Thought I might ask about it here since the site has given me much help.
the compressor won't engage though it can be turned by hand so it is not frozen. Also, it is climate control so the fan won't blow that hard, it does blow some weak cold air into the cockpit but nowhere near enough to cool the car, I imagine because the compressor is not engaging. I checked the pressure in the a/c system and it seemed ok, well over 25lbs on the low side.
Not sure how to proceed from there. Switch, sensor, which one, or new compressor, thought to ask before i spend a ton buying one part after another.
Thanks very much
tony
the compressor won't engage though it can be turned by hand so it is not frozen. Also, it is climate control so the fan won't blow that hard, it does blow some weak cold air into the cockpit but nowhere near enough to cool the car, I imagine because the compressor is not engaging. I checked the pressure in the a/c system and it seemed ok, well over 25lbs on the low side.
Not sure how to proceed from there. Switch, sensor, which one, or new compressor, thought to ask before i spend a ton buying one part after another.
Thanks very much
tony
Burning Brakes
Joined: May 2007
Posts: 965
Likes: 13
From: turn 12 at Road America or TX
Is the ECM turning the compressor on? There should be voltage (12?) at the clutch coil - if not, time to break out the FSM. Also, not sure how much pressure at the low side is needed to make the system work. Did it just quit, or was the compressor fast cycling and then no cold - if so, it's probably just low on freon.
Thread Starter
Instructor
Joined: Apr 2009
Posts: 118
Likes: 1
From: baltimore md
yes there is power at the green wire..even with the a/c off apparently
lasst time i checked i had power all the time at the green wire...top of compressor...the compressor spins by hand but won't go on its own.
the acceptable pressure low side is 25lbs for it to come on continually on full...
no it doesn't come on and circulate to off and back on..it just doesn't turn at all even with power to the green wire...
thanks very much for the ideas...I don't know exactly what could be wrong..
thanks
tony
the acceptable pressure low side is 25lbs for it to come on continually on full...
no it doesn't come on and circulate to off and back on..it just doesn't turn at all even with power to the green wire...
thanks very much for the ideas...I don't know exactly what could be wrong..
thanks
tony
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
Did you jumper the low pressure switch connection??
Try that and let us know........not sure what I am talking about? since there are 15 A/C threads currently going at once (must be summer)
rather than type all that info again
http://forums.corvetteforum.com/c4-t...-question.html
Try that and let us know........not sure what I am talking about? since there are 15 A/C threads currently going at once (must be summer)
rather than type all that info again
http://forums.corvetteforum.com/c4-t...-question.html
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
with the system not running 25psi does not really mean anything that is a static equlized pressure. You need to start by elimation. basics 12V at comp? if not 12V at low pressure switch? is so jump arcoss low pressure switch does comp run? it should and if it does you need recharged whitch I think is going to be your problem. again these are fast basic tests it can and may go a lot deeper then this but do the voltage tests first and cross the low pressure switch if you have what I said let us know where this takes you
Thread Starter
Instructor
Joined: Apr 2009
Posts: 118
Likes: 1
From: baltimore md
yes i did those two tests
indeed i did jumper the low pressure switch and check for voltage at the compressor. I jumpered the switch on my 80 to check that one and so i had learned about that switch earlier.
jumpering the switch did not help. the voltage at the green wire at the compressor is over 12 volts a bit..., I thought jumpering the switch would work, since the compressor is not frozen...but it did not work..that is why i am so puzzled...there is power to the compressor, yet it won't engage and spin...
that's why i think something internal with the compressor may be wrong.. just want to make sure there is no other relay or switch in between that should be checked first?
thank you for the great ideas...any others?
tony
jumpering the switch did not help. the voltage at the green wire at the compressor is over 12 volts a bit..., I thought jumpering the switch would work, since the compressor is not frozen...but it did not work..that is why i am so puzzled...there is power to the compressor, yet it won't engage and spin...
that's why i think something internal with the compressor may be wrong.. just want to make sure there is no other relay or switch in between that should be checked first?
thank you for the great ideas...any others?
tony
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Le Mans Master
Joined: Jul 2009
Posts: 6,381
Likes: 66
From: SF bay area C.A.
C4 of the Year Finalist
The clutch on your comp is most likely shot. On mine I have no power to the low pressure switch so I put in a manual switch in the cockpit to turn on the comp.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
The Low Pressure Switch is there to keep the Evaporator from icing over and the system from running when the charge is too low to carry the oil that lubes the compressor. I don't think you can out smart it.
25 lbs static..is zippo.
Le Mans Master
Joined: Jul 2005
Posts: 5,193
Likes: 16
figure around 80 to 100 but it will be determined by outside air temps. here's a good link that explains it..I keep a lot of these on my computer..http://www.aircondition.com/tech/questions/82/
Last edited by mfi; Jul 9, 2010 at 03:36 PM.
