fredster Posted June 16, 2004 Report Share Posted June 16, 2004 The clutch won't engage and it's HOT OUTSIDE!! I do have the GM service manual for my car and it has a troubleshooting flow chart. The first question that is asked is whether or not the AC relay cycles. How do I know this? thanks, Fred Quote Link to comment Share on other sites More sharing options...
Ranger Posted June 16, 2004 Report Share Posted June 16, 2004 Don't quote me on this but I think you should be able to hear the relay cycle (click). If not, swap it out with another one and see if it works. If so, replace the relay. If not, move on down the "chase around chart". Quote Link to comment Share on other sites More sharing options...
fredster Posted June 16, 2004 Author Report Share Posted June 16, 2004 Well, I listened at the relay while my wife turned cycled the AC on and off but I don't hear any click. So if I continue with the chart (as if the relay isn't cycling, I remove the relay, and jump two of the pins on the harness to see if the clutch engages, but it doesn't. Next step is this: "Check voltage at pin 'A' of compressor clutch" I can not seem to find where pin "A" is or whether or not it is even accessible. Not only that, how do you check the voltage on one pin? Also, what does it mean when the manual refers to CKT 509 (or CKT xxx)? Any help would be appreciated. Fred Quote Link to comment Share on other sites More sharing options...
Ranger Posted June 16, 2004 Report Share Posted June 16, 2004 I am not going to be too much help here. Chasing electrical problems is not my strong point. I just took a quick look at my service manual and I THINK pin "A" is on the compressor clutch. Which one, BTSOM! CKT509 = circuit 509. The problem is you have to search through the manual to find these things. You will have to find the right schematic to find CKT 509. You may also find "pin A" there. I once tried to figure out where to wire in a kill switch a few years back. I had 3 different pages referenced just to figure out the correct wire to cut into. I just gave up. Quote Link to comment Share on other sites More sharing options...
KHE Posted June 16, 2004 Report Share Posted June 16, 2004 Well, I listened at the relay while my wife turned cycled the AC on and off but I don't hear any click. So if I continue with the chart (as if the relay isn't cycling, I remove the relay, and jump two of the pins on the harness to see if the clutch engages, but it doesn't. Next step is this: "Check voltage at pin 'A' of compressor clutch" I can not seem to find where pin "A" is or whether or not it is even accessible. Not only that, how do you check the voltage on one pin? Also, what does it mean when the manual refers to CKT 509 (or CKT xxx)? Any help would be appreciated. Fred Did you check the A/C fuse? Did you jumper the proper two pins of the relay? There is usually a contact pinout diagram on the case of the relay that will indicate which pins are the contacts. The wiring diagram should identify the wire colors on the clutch plug. You will need to connect the negative lead of your voltmeter to the chassis ground and the positive lead to terminal A. If you have a digital meter you can connect a probe to each pin on the clutch connector - if there is voltage at the clutch, it may indicate -12 volts if the leads are reversed. The wiring diagram will have the CKT-xxx identified along the appropriate wire. You can then identify the wire color and location on the vehicle. Quote Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
KHE Posted June 16, 2004 Report Share Posted June 16, 2004 Have you entered diagnostics to make sure a low refrigerant code is not set? If the system is low on refrigerant, the compressor will not turn on in order to prevent it from damage. This is the first thing that should be checked. Simultaneously press and hold the OFF and PASSENGER WARMER buttons on the climate control panel and the codes will be displayed on the information center. Post back any codes. Quote Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
fredster Posted June 16, 2004 Author Report Share Posted June 16, 2004 Ah, I guess I forgot to mention a few things: By looking at the compressor, I see the clutch is not engaging. A/C comp fuse is good. I do not see any DTC codes except a couple of irrelevant ones. Part of my problem is not knowing how to use the service manuals. There is just so much info and some of it is a tad confusing. I DID find the section with all of the plug diagrams! And I see which is pin "a" on the clutch, so I will have to do that tomorrow. (woohoo!) As far as "check CKT xxx" ... I'm still not sure if I understand. I'm looking at what I think is the wiring diagram and I don't see "CKT" anywhere. I am guessing that the individual wires that have numbers will be the culprits? For instance CKT 59 will simply be the wire that is labeled as "59" on the wiring diagram? (which I do see on the diagram) And when the chart says "repair open in CKT 59, that simply means that there is a break somewhere in the wire? Is that it. Quote Link to comment Share on other sites More sharing options...
Ranger Posted June 16, 2004 Report Share Posted June 16, 2004 And when the chart says "repair open in CKT 59, that simply means that there is a break somewhere in the wire? Is that it. Yes that is correct. Re: the schematics, check a page forward or after where you are, the circuit your lookin for may be there. Quote Link to comment Share on other sites More sharing options...
fredster Posted June 16, 2004 Author Report Share Posted June 16, 2004 Larry, That's what is so difficult about these manuals, is that the diagram isn't anywhere NEAR the flow chart I am looking at -- in fact, it's in a different book! (there are two) But I am learning these manuals slowly but surely, thanks to my thumbing around in them and the advice I am getting here. I think with what I've learned tonight I will be able to get some more troubleshooting done tomorrow. For now, it's lights out! Thanks, Kevin and Larry, for your help! Quote Link to comment Share on other sites More sharing options...
Ranger Posted June 16, 2004 Report Share Posted June 16, 2004 Your response made me chuckle. Been there done that . Quote Link to comment Share on other sites More sharing options...
hiljak Posted June 16, 2004 Report Share Posted June 16, 2004 (edited) I'll describe the troubleshooting process that helped me and you should be able to track down your problem pretty easily (or at least isolate it somewhat). 1. Turn your a/c to auto and on high. 2. Go in to your diagnostic mode (hold engine off and warmer), look for any codes (particulary low coolant, if so got to step 4), after any codes, it will say PCM?, hit the fan higher button for the next menu then if the front defroster symbol is lit, the comptuer is telling the compressor to come on (powering the relay). 3.a. If it is lit but the compressor clutch is not spinning, try juming the two points on the relay socket closest to the headlight. If it now engages, you may have a bad relay or short between relay and compressor, or computer to relay. 3.b. If the defrost is not lit up on the above listed menu (with a/c supposed to be on), the computer knows the system is not charged. 4. Unhook the negative battery for 15 mins or so and then attemp to command on comressor. It should then spin, if the coolant isn't right, it should throw the code and kick off the compressor. (note that I also had a bad low pressure switch). this should get you goiing in the right direction. good luck. Edited June 16, 2004 by hiljak Quote James 1999 STS 65k 1995 STS 127k Link to comment Share on other sites More sharing options...
fredster Posted June 16, 2004 Author Report Share Posted June 16, 2004 (edited) Hiljak, Bbobynski had the same advice you just gave on this thread: http://caddysearch.netgetgoing.com/mbarchi...id=caddymb-3909 Here's what I saw in my '97 STS: When in the PCM section, I see on the climate control disply, only the "AC" and "AUTO" lit up above the front defrost button, an arrow above the "MODE" button and the REAR defrost light is lit. The front defrost light is NOT lit (which, accodring to Guru and you, is indicating that the PCM is not telling the clutch to engage, even though it should (yes, the a/c was on when I went in to the OBD.) Also, I don't seem to have an ACP section, as Guru refers to. There are NO codes set, though! I disconnected my battery and let it sit, then tried everything all over and got the same results -- no compressor, no codes (other than from disconnecting the battery), and same display on PCM section. I haven't had a chance to get under the car and check the voltage at the clutch yet, but I AM confused why the PCM doesn't seem to be telling the clutch to engage yet there are no codes set. ?!??!?!??! FYI - The codes that were set upon reconnecting the battery were: B1552 - Keep Alive Memory (KAM) Error B1558 - BCM EPROM Checksum Error Edited June 16, 2004 by fredster Quote Link to comment Share on other sites More sharing options...
hiljak Posted June 17, 2004 Report Share Posted June 17, 2004 Did you try to jump the compressor relay? It's under the hood, under the fuse panel (take the whole black panel off) then there is another small cover over the relays. You will see a "legend" on the inside of the black panel that shows what each relay is. Pull the compressor relay, then jump the two points closest to the headlight then see if the clutch is engaged. If it isn't, leave the relay socket jumped and check for voltage at the compressor. You are basically taking the computer out of the picture when you jump the relay. Hope this helps. Quote James 1999 STS 65k 1995 STS 127k Link to comment Share on other sites More sharing options...
Norton1 Posted June 17, 2004 Report Share Posted June 17, 2004 Oh yeah - my 94 STS did the same thing. Ended up being the high side limiter switch. It's one of those special pressure switches that you can remove from the AC line and replace by yourself without purging the system. It's up on the firewall right at the back of the hood. Has a single wire running to it. If that is what it is - don't buy one - I've got a spare (we just moved so I'll look for it tonight). I'll give it to you. Just let me know the part number so I know I'm sending you the correct one. I'll look through my mauals tonight to make sure the above info is correct. And don't feel bad - two GM techs went nuts on my car and they couldn't figure it out - I did by accident (and a lot of leafing through manuals that make no sense at times). And you check voltage by putting the red test lead on the pin in question and the black lead on any solid ground - metal part connected to the body/frame. Steve Quote Link to comment Share on other sites More sharing options...
fredster Posted June 22, 2004 Author Report Share Posted June 22, 2004 Well, everyone, problem solved. I had a bad connection at the compressor! Got my A/C back and I'm happy! Thanks to everyone for their help. Steve, thanks for the offer on the part. Mighty nice of ya! I sent you am email thanking you but don't think it went through. Quote Link to comment Share on other sites More sharing options...
Mr.D Posted September 29, 2019 Report Share Posted September 29, 2019 have a 2002 eldorado. ac clutch will not start. Push ac button but will not activate. I get a message that the refrigerant is low. Tried to recharge but it won't take in any refrigerant because I can't get the clutch going.Checked fuses and relays all seem to be good. How do I get the compressor operating in order to add refrigerant. Any help is appreciated Quote Link to comment Share on other sites More sharing options...
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