a/c problem
Thread Starter
Navigator
Joined: Apr 2011
Posts: 9
Likes: 0
a/c problem
I have a 1989 vette, the a/c worked for a while, but ive noticed the dispay on the climate control s sometimes shorting out, and as of last week all it will blow is hot air..The tech said the compressor is fine and it is full of fre-on ..however he said it was getting no power from the head climate control unit even when the fan was on High with the AC set on....He thinks it is the unit is bad...is there a way to fix it other then sending the unit out or what?
thanks
thanks
Burning Brakes
Joined: Apr 2009
Posts: 877
Likes: 0
From: Broken Arrow Oklahoma
Do you have the C68 option? Sounds like you do, but just want to check.
The control head goes through a few points before it signals the compressor to come on.
check the clutch relay (If it is the same as a 90)
The control head goes through a few points before it signals the compressor to come on.
check the clutch relay (If it is the same as a 90)
Burning Brakes
Joined: Apr 2009
Posts: 877
Likes: 0
From: Broken Arrow Oklahoma
the head unit sends a signal to the A/C heater programmer, that sends a signal to the clutch relay, that sends a signal to the ECM, that sends a signal to the high pressure switch, if there is the correct amount of gas it grounds the compressor and it comes on.
that is the condensed version of my 90.
the relay is mounted under the dash on the drivers side.
that is the condensed version of my 90.
the relay is mounted under the dash on the drivers side.
Burning Brakes
Joined: Apr 2009
Posts: 877
Likes: 0
From: Broken Arrow Oklahoma
check for 12 volts after the relay, that should eliminate everything before that.
It took me a couple of days and help from my friend toptech6 to find I had a cut wire from the ECM to the pressure switch.
It took me a couple of days and help from my friend toptech6 to find I had a cut wire from the ECM to the pressure switch.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
There's no Relay on an '89 with Electronic Controls nor does the Programmer have anything to do with the Compressor. Compressor is powered by the a/c fuse and a switched ground is provided by the Blower Control Module (which also controls the Blower Motor). It's mounted on the Evaporator Case. Control Panel has 3 circuits operating the Compressor. One goes to the Blower Module which switches on the ground. Another through the Hi and Low Limits. A third to the ECM for idle and WOT control. The later 2 have to be closed in order for the Panel to signal the Module; ie, the Control Reference voltage has to drop to 0 volts at the Panel on these 2 circuits for the a/c request to go to the Blower Module. Check the a/c fuse. Check for 12 volts on Black/White at the Compressor. Check that the Hi and Low Limit Switches are closed. Disconnect the Blower Module and check for 10 or more volts at Pin C2 (Green/Yellow) with the Panel at Auto 60 - that's the ground signal from the Panel. If it's there, replace the Module (which is more often than not the problem).
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
And PS - how in the heck does any Tech know that it's full of gas if it doesn't work? Static pressure is didly squat and it needs to be at operating temp; full blast and 1500 to 2000 rpms with the main fan cranking to tell if it's got what it needs in it.
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Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
As I said, on the Evaporator Case - that's the box protruding from the Firewall on the right side facing forward. There are two plugs or harnesses . through '89. connected to the Module. Follow the ground from the Compressor. NAPA usually has a stocking number or they're generally available in boneyards because they're not unique to the Vette. GM used the same electronic controls on Caddy, Buick, Pontiac & Olds - the only difference was the Dash face plate and Caddy probably had the largest number of units.
