i think this switch is dead. can’t seem to find replacement. in garage and parts book is across town. any one know where it is found. don’t see it on rock auto.

 

It is either on or next to the compressor.

 

the part in question is the hi side line mounted cut off switch. it is in addition to the one mounted on compressor. dual redundant safety system in this case.

 

I should have read your post a little better. You are trying to buy one...

Sorry

 

it happens, at least i know i be heard from my cave. . im thinking just about any gm switch would do as long as it has correct threads to screw on. i don’t recall if there is a schrader valve under it.

 

The pressure switch on the line from he condenser to evap is for the fans. It goes to the ECM and is tied to the fan switch in the pass head. It is normally open and closes to ground when it exceed 233psi (the compressor is chooching). It is screwed on to a schrader valve.

If I'm talking about is the part you're looking for, here are some....
https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15

If not, just ignore what I said as useless babbling about parts unrelated to your search...lol

 

yes! that is it. thanks! can i short the connector to see if the a/c is working?

 

You can put a jumper in the harness plug but, it has no effect on weather the a/c works or not. It's just an input to the ECM that says the a/c is on, you need the ECM driven fan to run. The tie to the fan switch driven fan, just bypasses the switch and ground the relay thus, both fans run when a/c is on.

The a/c compressor (by seeing your a/c has quit in your other post) works thru the cycle and high press switches only. The v6 cars (maybe the iron dukes ?) had a compressor relay. The v8 engines just passes power through the cycle.

Key in run, a/c on...

Look for +12v at the lt green and lt blue wire (each) on the cycle switch (plugged in, backprobe) or, test continuity across the cycle switch itself. . If the voltage/continuity is there, that switch is good.

If no power at the lt green, it may be an issue in the hvac controls not sending power to the cycle switch or, a fuse popped (doubt) Does the a/c work on other setting ? Max/Norm/Defrost.

If cycle switch/power is good, next is the high press cutoff at the back of compressor. Check for +12v at lt blue and dk green wire. Check continuity across switch. If it checks out, move to clutch plug power and ground.

The a/c clutch should lock down with the key in run and a/c on... power to the circuit is cut only in crank. HTH

 

only getting 27 mV to clutch

 

You need to test wire by wire looking for +12v.. it doesn't take a ton of power (watt) to make the clutch clamp but, it does at least require the voltage to be there. 27mv seems like open circuit.

You seem have an open in the circuit somewhere.Be it switch, plug or wiring

You can apply +12v to the dk green at the clutch to see if it clamps with no harm, too.

 

ya, i’m simply not getting 12V at compressor clutch. i shorted the pressure switch together ( which gets 12 just fine) and no joy at the clutch

 

That leaves the high pressure cutoff switch on the back of the compressor....

 

it is a close and working properly. good grounds everywhere. compressor wires also check out as good. i’m screwed! what about the diode?

 

What is the Air Conditioning Cutout Relay ? - The Service Manual refers to this in 1B-13 Says the ECM will open the relay contacts if certain conditions are met, such as WOT or excessive engine heat - which is what occurred to me the other day, wonder if this relay is stuck open now?

 

According to my factory service manual, the A/C cutout relay is located on the left (drivers) side firewall, to the left of the brake booster. There are several relays there, it is the one most outboard (closest to the fender).

 

what page are you seeing that on? I'm beginning to wonder if V8's have one?

 

1B-38

 

Ah! Thanks! I see V6 engine has 3 relays including the A/C relay in that area on page 6D5-8, but when looking at LB9/L98 (pg 6D5-13) the a/c relay doesn't exist. Not at my car to verify.

The diagrams starting on page 8A-64-0 also confirm this.

 

Here's a photo...

 

looks like we have the same book. the book in other areas leave this relay out for the LB9/L98, as if it was only used in the V6. i can visualize the relays over there, but don't recall how many. not at my car to confirm.

 

Ha! Found a picture. It does indeed look like there are 3 over there. Why the book leaves the a/c relay out in other diagrams for the LB9/L98 is a mystery. will have to double check that once I get to the car.

 

I just popped the hood on mine and checked: no relay there. I believe you're correct; only on V6.

 

I think I see 3 in mine, now I'm really confused!

 

Rock Auto is showing this relay available for the LB9

 

I just re-read Orange Bird's post #8 on how this works, he mentions that only the V6 had this relay.

 

The plot thickens. I found another photo of engine bay that confirms I have 3 relays over there. makes me wonder if the vehicle had gone in for service before I bought it and one was installed. I've owned the car since 92, and I know I didn't put it there. But............the parts book shows the a/c compressor relay being there. item #13

 

That's really strange! My manual (Page 8A-64) circuit diagrams show only the V6 car as having the compressor control relay. V8 cars do not. There is a procedure to test the relay described on page 8A-64-6.

 

I am seeing the same thing in the manual, just not the car (maybe) I'm heading over to it in a while and will check it out. thanks for the help and the procedure. this would be much easier to fix than an ecm problem or locating a wire that has gone rouge. it also makes sense with what I experienced the other day.

 

It is only the v6 cars, all years, with the relay. The diode just prevents voltage spikes from the compressor clutch cycling.

If there is 12v+ at the lt green with on the cycling switch on the accumulator (dryer, w/e), with the key in run and hvac control set to a/c, and not at the clutch, you have a open in the circuit somewhere.

 

I was looking at photos of my engine bay and see 3 relays over there. Not at car to see what they are about, but I'm beginning to wonder if I may have that relay. Heading over there soon to find out.

 

Hi LiquidBlue ,
It is true that only four and six cylinder cars got the AC compressor clutch relay , it was not used on the 8 cylinder cars .

However , the fact that the 8 cylinder doesn't use an AC clutch control relay doesn't mean that your car shouldn't have 3 relays in that location . The fuel pump relay and the radiator fan relay are always 2 of the relays mounted in that spot , and on the four or six cylinder the third one is for the AC . On MAF equipped 8 cylinder cars I've seen the third one be for the MAF , and I'll bet different optioned cars had different relays mounted in that spot as well , that spot seeming to be GM's catch all spot for whenever some option or other called for a relay .

Edited to add , looking at your wiring diagram I'm left wondering if your third relay may perhaps be the relay for the second (AUX) radiator fan ?

 

good call. that is exactly what is. where in the service manual do you find that page you posted?

 

I'm happy to have helped , and the diagrams I post are all shamelessly borrowed from a site called "austinthirdgen" . If you search out that site and go to it's "tech info" area they have most of the 82-92 diagrams

 

i know that site. in the last diagram i posted, should i read o ohms between lt blue of pressure switch connector and lt blue of ac high pressure switch?

i don’t really know how to read these diagrams

 

Yes , you should read 0 ohms between the light blue wire leaving the pressure cycling switch and arriving at the opposite end of the A/C high pressure switch . If you read any higher than say .01 of an ohm there is a bad connection in one of the two connectors .

 

think i figured it out. just made an improvement to the service manual. Lol. i may be getting false readings from hi pressure switch. thought it was closed, but sometimes i read open

 

brand new switch pins not right. i filed them a bit a cleaned up with cotton swap doused in acetone. have 12 to the compressor!

 

Awesome , very happy to hear that !

 

thanks for all your help and inspiring me to keep trudging on the r134a conversion. now back to that road test!

 

 

Good to hear (read) you were able to find the problem