Hey All,

Quick question....I'm having A/C problems with my '90 coupe....compressor won't power up....fuse recently blew that controls 12v stuff like cig lighter, power antenna, dash A/C control etc., replaced fuse (compressor didn't power up before fuse blew)....everything works now....fan speed and temp controls ok....100lbs. pressure....compressor still will not power up....no current to pigtail via test light....fuse is fine....also disconnected battery to reset "brain"....no luck....replaced clutch about two years ago....what's up???? Any tips would be much appreciated....thanks in advance.

Dean


[Modified by badnewstravelsfast, 9:19 PM 8/21/2002]


[Modified by badnewstravelsfast, 9:48 PM 8/21/2002]

 

Come on....I'm sweatin' here!!!!lol

 

Power to the a/c clutch is from the a/c fuse, through the clutch coil and back to the blower control module which supplies a ground to energize the coil when a/c is requested. Both wires through the clutch should have battery voltage with ignition on at all times. Check voltage again with a DVM. If there is no voltage on the wire from the fuse, find the short and repair the wire. If there is no voltage on the wire from the coil to the blower module, the clutch coil may have shorted and will need to be replaced. My guess is that the fuse blew because the coil shorted.

 

Any more ideas!?!?!?

 

check high/low pressure switch, they are there to protect the compressor from too little or too much charge. Sounds like you have low charge.

 

Hey fasteddez....thanks for the tip....not to sound ignorant, but what is and where is the high/low pressure switch and how do I check it....I am fairly mechanically literate but know NOTHING about A/C....Thanks Again!

 

High pressure switch (small tube) should always be closed.
Low pressure/cycling (big tube) switch will come and go. There is probably a fan/realy switch on your system,.... try not to get confused.

There should be enough pressure in the system to keep the low pressure switch closed, with the system idle (no compressor spin). If not, switch is bad or you are low on refridgerant.

 

Thanks All,

I have about 100lbs of pressure in the system....it seems electrical in nature to me....I ran a test light to the pigtail at the compressor and got nothing. The fuse is fine....I'm stumped :confused:

 

Try this, with the key on but the engine off, do the following test.

1 remove the low pressure switch and use a small 18 gauge wire to jumper the connector terminals, also use an ohmeter on the switch blades to see if you have continunity.

2 with the connector jumped, go turn on the key, put the a/c to 60 and fan on high. if you do it alone, note the clutch position on the compressor and the clearance. if the switch was bad on the low pressure line, the clutch should pull in. if not, i think the 90's have a relay that could be faulty and I do not have a 90's manual. I will look in my brothers 89 and see where it is located. other may state it in response.

3 if the clutch did not pull in I would find that relay if you are sure you have a good fuse. you should be able to put 12 directly to the compressor plug and see if the clutch pulls in without the engine or key on. if the clutch pulls in under this direct voltage you have the relay or wire open somewhere. send me an email if you want additional help.. good luck.

OK, looked in a 92 book and there are four large relays grouped together on the left front wheel well. as you read from left to right looking at the relays the 1st is relay #4 a/c low blower relay, #3 is a/c high blower relay, #2 is 1-4 gear relay on 6 sp with c60 controller, #1 is the compressor relay. check the numbers of the relays, some are the same and interchangeable to test and see if it is bad. If you have an automatic, you only have 3 relays and the 1-4 is missing. if you have c68 controller and manual, there are only two relays and if you have c68 only 1 relay. good luck....keep in touch if need more info.


[Modified by C4TOMCAT, 3:09 PM 8/23/2002]


[Modified by C4TOMCAT, 3:11 PM 8/23/2002]

 

Thanks C4TOMCAT....I may take you up on the email....I'll be fiddlin' with it on Sunday.

 

Hey C4TOMCAT....Thanks again for your reply to my post....unfortunately I fiddlefarted around with it and did everything you suggested to no avail....here's what happened
1) Jumped the Low Pressure Switch....nothing
2) Ran 12v directly to the clutch and it moves in and out just fine
3) Checked pigtail to compressor....nothing
4) Did a code test at the in dash LCD by holding the "up and down" fan buttons for 5 seconds and then the "auto" fan button and got a "00"which I'm told = no code or okeedokee!

In your post you mentioned a bank of three relays....couldn't locate them....remember....mine is a '90 L98 Coupe, Auto....It says in your post that you looked in a 92 book....is it the same, and could you possibly be a little more specific on the location of the relays in question?

Finally...my neighbor....who will remain nameless to protect the innocent....has a friend in the 'vette salvage business who tells him there is somekind of "small black box" as he calls it, located somewhere in the dash behind or to the side of the control unit that if goes bad will not allow power to the compressor :confused: wut's up wit dat :confused: any additional info will be much appreciated....especially by my girl who....well....is a "girl"....hates the "no A/C" thing :smash:

Thanks again in advance

 

Does anyone know the location of the A/C compressor clutch relay (part #25520198) on my '90 L98, auto coupe???? I'm goin' nuts tryin' to find it. C4TOMCAT has been a HUGE help in trying to pinpoint my problem....he thinks it might be the relay in question....thanks in advance for any help!

 

I believe the AC clutch is supplied a constant voltage directly from the fuse box whenever the ignition is on, the blower control module on the top of the blower housing controls the grounding of the circuit to turn it on, but that gets a sig. from the heater/AC control box in the dash that gets input from the A/C high press switch and press cycling switch and of course the driver. The blower control module is last in line.

 

Thanks Maximus....I'll give it a shot!

 

If you find the solution, please pass it on.
I have been through the same thing with my 90 and it I am pretty much glad winter is almost here.
My case is somewhat similar, except my compressor kicks in when it feels like it, not when I tell it to. I could be driving and ill put the A/C on (knowing it wont instantly turn on) and just wait till she feels like cooling me off.
So I can feel for you. If you do find the solution, please let me know for I think it is a very similar case.

 

Sounds like you're low on gas. Engine heat raises pressures and in your case, sufficient enough to close the low pressure switch which then turns on the compressor. You need to hook up some gauges and read your operating pressures, monitor the clutch for engagement. If you haven't added any freon in 12 years, you're probably long overdue for a leak check and a recharge.