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Thanks all. Family life got in way of C5 life this weekend. As for being low on refrigerant, I realize its low, but it wont take anymore from the refill can when I try because compressor never engages. Several of you guys know more about this than I do. Just because I have a set of gages and a refrigerant "sniffer" doesnt make me an expert! Thanks much for the help. I do believe that the compressor is not getting any electrical signal. Does anyone know if the electrical connector at the compressor is accessible from the passenger side wheel well if that tire is removed? I DONT want to pull the rack! AGAIN!! I did have a major oil leak, caused by a bad compression fitting, that did oil most everything in the front and sides of the engine. However, nothing else was effected (yet!), if this is the root cause. I'm starting to think whatever sends the signal to the compressor isn't doing its job. I have the electronic climate control, and everything else, like blowing air in right places, high and low temperatures, work good.
YES !!...the connector can be accessed and removed if you remove the tire...looks like a straight shot in !!
FIRST see what your low side reads after the car has been sitting for a while when you hook up the gauge set...low side pressure should read close to the outside air temp...have you checked this recently since the AC hasn’t been working ??...if good I’d remove the relay and jump pins 87 and 30 (pictured) at the fusebox. The terminal numbers are on the bottom of the relay but they normally sit diagonally across from each other...first I’d see if you have power at 87 and 30 is the ground G102 which goes into the splice pack 100 which is behind the R/H headlight....if that doesn’t work you’ll have to check for power down to the compressor or if you have a bad ground...if jumping 87 and 30 engages the AC clutch with key ON...you will hear it click !!...you should see if you have power at pin 86 or 85 at the relay...can’t remember which one but you’ll always have 2 terminals at a relay that should have power when the key is ON. Also you may have issues with the AC pressure sensor which sits aft of the high side Schader valve....just back probe the signal wire (red/black)...you can stick a safety pin into the back of the connector....you should have 1 volt with AC off at idle and 2.8-2.9 with AC on !!...if the clutch is engaged see what our high side reads...290 psi is good...if 290 psi with compressor running but have 1 volt our pressure sensor is bad !!...if you were to disconnect this sensor you would have the AC light come on for 3 seconds and go out !!
Ive finally got time to check out the the terminals mentioned in your post. Not to sound stupid, but the terminals you have identified, do I put the positive probe from DVM on one, and ground the DVM black probe? Then repeat on other terminal? Or put one DVM probe into one terminal and put other probe into other terminal? I'm guessing first combo I asked about is correct. Thanks, all
Hey guys, I also wanted to know if anyone knows how to bypass the pressure switch. Could you insert a paper clip, or is this switch normally closed? I did try unplugging it and it made no difference.
FIRST see what your low side reads after the car has been sitting for a while when you hook up the gauge set...low side pressure should read close to the outside air temp...have you checked this recently since the AC hasn’t been working ??...if good I’d remove the relay and jump pins 87 and 30 (pictured) at the fusebox. The terminal numbers are on the bottom of the relay but they normally sit diagonally across from each other...first I’d see if you have power at 87 and 30 is the ground G102 which goes into the splice pack 100 which is behind the R/H headlight....if that doesn’t work you’ll have to check for power down to the compressor or if you have a bad ground...if jumping 87 and 30 engages the AC clutch with key ON...you will hear it click !!...you should see if you have power at pin 86 or 85 at the relay...can’t remember which one but you’ll always have 2 terminals at a relay that should have power when the key is ON. Also you may have issues with the AC pressure sensor which sits aft of the high side Schader valve....just back probe the signal wire (red/black)...you can stick a safety pin into the back of the connector....you should have 1 volt with AC off at idle and 2.8-2.9 with AC on !!...if the clutch is engaged see what our high side reads...290 psi is good...if 290 psi with compressor running but have 1 volt our pressure sensor is bad !!...if you were to disconnect this sensor you would have the AC light come on for 3 seconds and go out !!
SORRY!! Jump means JUMP-DUH on ME. Anyway, I jumped 87 & 30, and the clutch clicked!!! It's a bad Hi side sensor, or???
If the clutch engages when you jump the relay, then whatever is happening, is happening in the control side of it. If it doesn't, THEN check the connector.
If you decide to check the refrigerant pressures, I suggest you connect your gauges first and then start the car and jump the relay. Since you are temporarily bypassing protections, you want to be able to keep an eye on both pressures at all times to avoid any potential damage.
So, since jumping 87 and 30 did engage compressor clutch, does this mean my dual climate control head unit is bad? Could I check the other 2 terminals of this relay by checking for 12v? Say using DMM to check 1 terminal for voltage, and other one for continuity to ground? If so, which one is the 12v terminal, and which one is ground? I'm assuming that when I swapped fuel pump relay with a/c relay, and fuel pump still worked, it's not a bad relay. Does it matter which way relay plugs into fuse box? I'm guessing not, because some relays have a fifth terminal so they can't be plugged in backwards, and these 2 relays do not. Thank you for all the help.
Hey guys, I also wanted to know if anyone knows how to bypass the pressure switch. Could you insert a paper clip, or is this switch normally closed? I did try unplugging it and it made no difference.
No No No !!...it is NOT a switch but a pressure SENSOR and don't jump anything !!!...that 3 wire sensor has a 5 volt reference, a signal wire, and a low reference (ground) to the PCM...first you'll have to jump 87 and 30 for a few seconds to make sure the AC isn't working because of low pressure or even high pressure....if the pressure looks OK you can concentrate on the pressure sensor possibly being bad. Remove the connector on the sensor and take your volt meter and measure between the gray and black wire...if it's 5 volts we know that the power and ground are both good...now plug the connector back in...you have to get a safety pin or something sharp and insert the red lead of the volt meter into red/black wire and connect black voltmeter lead to a good ground...with key on and engine off read the voltage...should be roughly 1.2 volt !! (see pic)...with car running an 87 and 30 jumped voltage should be around 2.5 volts if your high side pressure is around 250 PSI !!...post your voltage readings !!...I posted a pic of the signal wire back probed...you can but them and they are pretty cheap !!
Thank you so much for being patient with me. I'm not a young guy anymore, but I do want to help other forum members as well as myself. It just may take a few days. I'm hoping that before long, my biggest problem will be getting in and out of the car-And trust me, that IS becoming a problem!! lol-btw.....Nice voltmeter!!
Thank you so much for being patient with me. I'm not a young guy anymore, but I do want to help other forum members as well as myself. It just may take a few days. I'm hoping that before long, my biggest problem will be getting in and out of the car-And trust me, that IS becoming a problem!! lol-btw.....Nice voltmeter!!
I’m probably older than you...LOL !!...I PM’ed you my number...give me a buzz !!...that Vantage Pro measures just about everything in a car you can imagine and also a scope but only mediocre !!..one of my favorite tools !!
I’m probably older than you...LOL !!...I PM’ed you my number...give me a buzz !!...that Vantage Pro measures just about everything in a car you can imagine and also a scope but only mediocre !!..one of my favorite tools !!
UPDATE on A/C problems.......
After spending this afternoon on the car, and with a LOT of input from C5 Diag (thank you very much Rob!), this is where I am:
I hooked up my gages to the unit, and jumping pin 87 to pin 30, I got the A/C clutch to engage. I put about 10 ounces into the system, and the low side read 90psi, the high side read 100-105psi. Test conditions were approx. 85 degrees outside. I then pulled my jumper pins and put the relay back in. C5 Diag and I have come to conclusion that there are 2 separate issues here;
1: The compressor is apparently shot, and as I said earlier, it is 20 years old.
2: Something somewhere on the control side is preventing the A/C clutch from engaging.
I'll have to give it up for a couple days now. I've checked the hi sensor harness and have the 5v signal between the gray and black wire, and .7v on the red wire. Took the car for a short drive and when pushing the a/c button, the yellow light comes on and stays on-When moving. At a stop it goes out, then comes back on for 3 or 4 seconds before it goes out again. But the clutch is NOT engaging no matter what the light says. There also was no metal in the orifice tube when I checked it last week. At this point, I'm out of ideas.
You really got some things checked out today so now we know that your compressor is most likely toast so you’ll have to concentrate on the wiring... the only thing I can suggest without a scan tool to determine if the PCM is grounding the AC clutch relay control circuit (the control side of the relay) is to wrap some thin copper wire around pin 85 of the relay and insert it back into the fusebox...now take your 12 volt test light and connect it to battery POSITIVE...wrap the copper wire around the tip of the test light...when you command the AC on with the car running the test light should light indicating that the PCM is grounding the circuit..if you can find someone with a Tech 2 that would be even better...there are 3 data PIDS to look at with the Tech 2....AC relay command (ON), AC request (YES), and AC status (ON) when you turn the AC on !!...did you notice if the cooling fans kicked on when AC was selected ??...like I said I’m not sure of the PCM’s logic regarding ambient temperature for AC turn on...I think it’s around 37 or 38 degrees or something...I do know is when I disconnected my ambient temp sensor the AC continued to operate however the HVAC module shows 68 degrees...I may have to drive the car so the ambient temp will update !!,..I’ll have to research that..,maybe someone might be able to shed some light on this !!
You really got some things checked out today so now we know that your compressor is most likely toast so you’ll have to concentrate on the wiring... the only thing I can suggest without a scan tool to determine if the PCM is grounding the AC clutch relay control circuit (the control side of the relay) is to wrap some thin copper wire around pin 85 of the relay and insert it back into the fusebox...now take your 12 volt test light and connect it to battery POSITIVE...wrap the copper wire around the tip of the test light...when you command the AC on with the car running the test light should light indicating that the PCM is grounding the circuit..if you can find someone with a Tech 2 that would be even better...there are 3 data PIDS to look at with the Tech 2....AC relay command (ON), AC request (YES), and AC status (ON) when you turn the AC on !!...did you notice if the cooling fans kicked on when AC was selected ??...like I said I’m not sure of the PCM’s logic regarding ambient temperature for AC turn on...I think it’s around 37 or 38 degrees or something...I do know is when I disconnected my ambient temp sensor the AC continued to operate however the HVAC module shows 68 degrees...I may have to drive the car so the ambient temp will update !!,..I’ll have to research that..,maybe someone might be able to shed some light on this !!
Good morning. As for the fans on or off, I believe they come on at low speed on a properly operating system, which mine was until a month ago. However, when I jumped pins 87 & 30 yesterday as you advised, I heard the fans come on at high speed. Hope this helps.....
Hi Mike !!
Ok, great !!...also now that we know relay terminals 87,30, and 86 are good now we just have to figure out if the PCM is grounding the relay control circuit at pin 85...you can try what I had suggested in my post previously !!
Hi Mike !!
Ok, great !!...also now that we know relay terminals 87,30, and 86 are good now we just have to figure out if the PCM is grounding the relay control circuit at pin 85...you can try what I had suggested in my post previously !!
Hi Rob. I assume you're talking about wrapping the wire around pin #85, and checking ground with test light at negative battery post. I also assume I have to press A/C button to activate system to see if pcm is grounding.
Hi Mike !!
Ok, great !!...also now that we know relay terminals 87,30, and 86 are good now we just have to figure out if the PCM is grounding the relay control circuit at pin 85...you can try what I had suggested in my post previously !!
I'll pick up a test light on way home from here. "Here" is at GM STEALER with other car. Some covered under warranty, but around $1,400.00 is NOT!!!! Oh well, there goes my new A/C compressor!!!! This hasn't been a good week at all!!!!!! But crying only adds saltwater to the terminals lol.....
Hi Rob. I assume you're talking about wrapping the wire around pin #85, and checking ground with test light at negative battery post. I also assume I have to press A/C button to activate system to see if pcm is grounding.
Remove the relay and wrap the wire around pin 85...the last one we haven't checked...reinsert the relay with the wire wrapped around it and now connect the test light alligator clip to battery "POSITIVE"...wrap the end of the copper wire around the tip of the testlight....now start the car and turn the AC on...if the PCM is grounding pin 85 the 12 volt test light will light up !!...if you are not sure when I get home from work I can send a picture or do a quick video of what it will look like !!
...I checked fuse #24, and it's good. I swapped the fuel pump relay out with the A/C relay, since they're the same relay. Since the fuel pump still works, the relay is O.K.. But of course the compressor clutch still won't engage...
So it's been established that Relay 34 is fine.
Originally Posted by C5 Diag
...now that we know relay terminals 87, 30, and 86 are good now we just have to figure out if the PCM is grounding the relay control circuit at pin 85...you can try what I had suggested in my post previously !!
It seems it was also established that Relay 34's pin 86 had battery power from CKT 739.
Originally Posted by grinder11
...I assume you're talking about wrapping the wire around pin #85, and checking ground with test light at negative battery post. I also assume I have to press A/C button to activate system to see if pcm is grounding.
Actually it would be at the positive battery post. You can do that, but we already know the answer: pin 85 is not being grounded. Either the PCM is not providing ground to Relay 34's coil, or CKT 459 is open at some point between the PCM and Relay 34's socket.
Look at the circuit below. You already verified that by jumping together CKT 739 and CKT 59 (Relay 34's pins 87 and 30) the compressor clutch gets engaged, that means the control side of the relay is not commanding the clutch. Since it was determined the relay's coil is getting power from CKT 739, the only thing that can prevent Relay 34 from being activated is the lack of ground on the other end of its coil.
You can check the integrity of CKT 459 by verifying continuity between Relay 34's pin 85 and PCM connector C1 Pin 39.
To determine whether or not the PCM is providing ground you would need to back-probe PCM connector C1 Pin 39 with your test light, but if CKT 459 is fine, it would be redundant because it would have to be that there's no ground.
It seems you already tested the refrigerant pressure sensor. Is your outside temperature sensor working fine? The A/C compressor won't engage when outside temperature is below 35°F to 40°F. If the sensor is bad this is a possibility.
Another possibility is that the PCM would not be receiving the corresponding command from the HVAC control unit, via the Serial Data Bus.
Yes !!!...load side of relay is good !!...pin 86 has power...if the check I asked the OP to do does not work he will have to check if there is an open in the circuit and also by checking at the PCM...I don’t think the OP checked the sensor with the compressor engaged and checking the voltage...it was only checked key on but needs to be checked with the compressor engaged and engine running...if 400 plus psi disengages the AC compressor we need to know the voltage....2.3 volts or so is 250 psi so anything near the 5 volt ref is no good...if the ambient temp sensor is disconnected you’ll see 68 degrees or so on the HVAC head... I believe that temp will not update unless you go over 25 MPH or some speed near that...I’m assuming this is a “substituted value” if you are familiar with this term...if you look on the “generic OBD2” side with a scan tool the PCM will show the actual value which being a thermistor should show minus whatever temp...I’ll have to look at that value is !!...I did a quick video for the OP on how to check the control relay control circuit and will try to upload it soon...thanks !!
