1995 coupe A/C comp. runs always

[jmccloud]

My 1995 coupe a/c compressor runs all the time even though the heater/ac control is turned off or to heat. I've replaced the a/c relay behind the r/f tire. My interim solution is to unplug the compressor. Any ideas?

Background info: I've had it about 10 months. Best car I've owned. The car has standard heater a/c control. Cools nicely in the summer. The compressor will begin cycling and eventually shut off as the exterior temperature approaces and drops below 40F. So the low pressure cutout is functional. Unplugging the compressor improves performance noticably so I'd like to remedy the situation and eliminate having to raise the hood.

[vigman]

This happens from time to time

Vig!

[jmccloud]

Compressor relay was replaced. Both the original and replacement (new) worked well in other applications.

Or, is there more than one relay???? .

[vigman]

For a 93 is located right side of engine compartment mounted to inner fender well.

Do you have Auto or stick..assuming not ZR-1

LT-1

For an auto car electronic A/C there is only 1 relay

For an auto car with MANUAL A/C there are 3 relays it's the last relay ( end of harness )

For a stick car with electronic A/C there are 2 relays.. it's the one NOT at the end of the harness.

For a stick car with MANUAL A/C there are 4 relays.. it's the second from the last ( end of harness.

PHEW

So remove the relay for now... and replace it

If it still clicks ON

Then you have a controller problem.


Vig!
( post your findings )

[vigman]

So you DID replace the A/C relay and you got the correct one ...right?


Let me look some more



Vig!

[jmccloud]

It's an automatic shift with a manual a/c control. Thanks for the relay info. That's the one I replaced.
Any suggestions on 'controller problem'?
Thanks for the input

[vigman]

Does the clutch kick off?

Here's the deal

On the relay 4 pins
85 Brown ( Hot in run position) one side of coil
87 Brown ( Hot in run position) swinger of relay

86 Dk green white
Low side of coil to ECM
this line goes to gnd when AC is called for

30 Dark Green
Normally open line in relay.
When relay bangs shut this line goes HI ( hot ) and supplies power to the clutch.

There are further tests.. but we need to verify that this is in tact..I'll bet its a sender!

Vig!

[vigman]

Be right back

I assume you have a volt ohm meter and know how to use it?



Vig!

[jmccloud]

Thanks for the inputs, keep it coming. Yes, have VOM, scope, etc. Wife says dinner company is here and must log off (likely until tomorrow).

[vigman]

Get you ohm meter ready.

Open hood
Passenger side of the car

look at the shinny lines ( aluminum) going to the AC box on the firewall.

There are 2 size lines

BIG=suction=Low side
small=pressure=High side

Near the top of the A/C blower box is a 2 pin sender mounted to the low side line.

It has a Light Blue & a Dark green/yellow on the 2 pin connector on that sender.

Locate this sender!


Now start the car ( ac relay connected )

Disconnect the sender via the connector.

Did the compressor quit?

If yes...continue

Shut car off.. key in off position

Get your OHM meter and measure the Light Blue line In reference to ground.

You should read "O" ohms ( short) in the following positions

MAX
Norm
Bi-level
And
defrost

Vent & heater should show that line OPEN.

Do this test, I will advise


Vig!

[vigman]

Will the wife be PO'ed

Stay tuned for the exciting conclusion of JM's AC

Live on CAC net.!


LOL

Vig!

[vigman]

Now knowing how GM works

this PROBABLY is the same circut in a 95.

( giving myself an out here)


So I'll bet ( and this is a wild guess ) that the relay is fine, and your previous post states the low pressure switch MIGHT be fine ( since it cycles) but this COULD BE from a high side issue.

and the switch in the head is toast
( Ohhhh bad call Vig!).

So if the last test shows ALL the positions show ground that line...out the dash comes.

( Oh boo hiss....)


Vig!

[jmccloud]

The blue wire has 12v any time the key is on (heater a/c controls tried in all positions including off). When the receiver/dryer gets warm enough, the low pressure sensor closes and 12v is supplied to the green/yellow trace and the compressor clutch pulls in to run the a/c. It's cold here so it takes some warming to get the low pressure sensor to close.
What feeds 12v to the blue wire?

[vigman]

The light blue SHOULD be ground or open NOT +12 volts this MIGHT be an indication that the electrical systems are different.

to Quote Scooby -Doo

RUT-ROO


Vig!

[vigman]

Is NOT on thr reciever dryer!


Vig!