crazyd Posted March 30, 2013 Report Share Posted March 30, 2013 Went to charge the A/C on my '92 GTP for the season and opened a can of worms. I've had a slow leak for a long time, but it works for the 3 weeks or so that's all the heat waves we have up here last. This time though, the compressor wouldn't engage. So I replaced the compressor relay. No dice. Next I thought I'd change out the pressure switch, and I cracked the line at the schrader valve for the switch. So I changed out the line and found damaged O-rings that were probably responsible for the leak. Replaced the O-rings, installed a different pressure switch, vacuumed it down, it held 25in for 10 mins no problem so I charged up to 50psi on the low side. Hit MAX, compressor still wouldn't engage. Okay, try the compressor then. Changed it out, confirmed the electrical connector was secured. Vacuumed it down, again it held 25 in for 10 mins so I charged to 50psi and tried again. Still won't engage. I have pressure on the high side too, gauges are showing +10. The only thing I've done since last year when it worked was change the alternator to a new CS130D with a self-exciting regulator that doesn't need to be plugged in. Don't see how that could affect it - sure hope it doesn't. I'm out of ideas - any suggestions? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted March 30, 2013 Report Share Posted March 30, 2013 are you forcing the compressor on manually, or is it still under PCM control? Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted March 31, 2013 Report Share Posted March 31, 2013 Car needs to be running with AC on max and fan on full to charge any AC system. Quote Link to comment Share on other sites More sharing options...
crazyd Posted March 31, 2013 Author Report Share Posted March 31, 2013 Rob, it's still under ECM control. If I vacuum it I have never needed to force it to engage if I get the presssure above 30psi. And yes, as I said I had it on MAX... Quote Link to comment Share on other sites More sharing options...
55trucker Posted March 31, 2013 Report Share Posted March 31, 2013 At this point...........assuming that there are no other electrical switch problems, is the power steering compressor switch trouble free? It is a normally *open* switch, it provides a signal to the ECM to cut the A/C compressor when high steering loads are present that can affect idle. Quote Link to comment Share on other sites More sharing options...
crazyd Posted March 31, 2013 Author Report Share Posted March 31, 2013 I've been mulling that one over too, Steve. Unless the compressor engages, there's no easy way to test if the power steering pressure switch is cutting out the compressor like it should. I'm sure it's plugged in. On another thought, using a connector I cut from the harness of a W in the junkyard today, I put 12V to the previous compressor I removed to test its clutch, and it engaged. I want to try doing the same thing to the replacement one I have just to be sure, but it's going to require lengthening the wires first. I'm sure it will engage too. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted March 31, 2013 Report Share Posted March 31, 2013 why not just jump the relay terminals? that's how i force a compressor on. Quote Link to comment Share on other sites More sharing options...
crazyd Posted March 31, 2013 Author Report Share Posted March 31, 2013 What's the point of having a charged A/C system if the compressor doesn't run? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted March 31, 2013 Report Share Posted March 31, 2013 just suggesting an easier way to verify that the compressor works, rather than crawling under and disconnecting the harness. Quote Link to comment Share on other sites More sharing options...
crazyd Posted March 31, 2013 Author Report Share Posted March 31, 2013 It's fairly easy to access the plug from above on a DOHC. Jumping the relay is a good idea, but there's four relay terminals - which two should be jumped? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted March 31, 2013 Report Share Posted March 31, 2013 pins 3 and 5 are the switched load. http://imgur.com/a/ah5nb jump those with your key in the run position and it should actuate the clutch. Quote Link to comment Share on other sites More sharing options...
crazyd Posted March 31, 2013 Author Report Share Posted March 31, 2013 Tried it, got nothing. Quote Link to comment Share on other sites More sharing options...
White93z34 Posted April 1, 2013 Report Share Posted April 1, 2013 put a lamp on the compressor clutch plug and see if it lights up when you turn on AC? that should narrow down it being a few bad clutches or a car wiring issue. put a multimeter on the clutch and verify the coil is not open as well. Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 1, 2013 Report Share Posted April 1, 2013 Here Dave: take a peek at these.... perhaps they will help you sort this conundrum out. Quote Link to comment Share on other sites More sharing options...
crazyd Posted April 2, 2013 Author Report Share Posted April 2, 2013 That's a lot of info to digest, but I ran the power test and instead of battery voltage I get only 1.4V on pins 1 & 3. Both IGN fuses test good with the meter (I couldn't get them out with my fingers to check visually). Think I've found the culprit, but why would I get a low voltage like that? This is starting to take me back to my alternator problem, where its regulator was not activating because of low voltage on the exciter circuit there as well. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted April 2, 2013 Report Share Posted April 2, 2013 that kind of voltage would be seen with a partially broken wire somewhere between your test points. or maybe a dead fusible link/fuse. Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 2, 2013 Report Share Posted April 2, 2013 (edited) That's a lot of info to digest, but I ran the power test and instead of battery voltage I get only 1.4V on pins 1 & 3. Both IGN fuses test good with the meter (I couldn't get them out with my fingers to check visually). Think I've found the culprit, but why would I get a low voltage like that? This is starting to take me back to my alternator problem, where its regulator was not activating because of low voltage on the exciter circuit there as well. You need to get that 15 amp fuse out of the socket for pins F3 & F4 in the right side elect. center and check pin 3 for battery voltage, It should be live with the ign switch to *run*, if it is not then there's a problem upstream between the electrical center & the ign switch. Edited April 2, 2013 by 55trucker Quote Link to comment Share on other sites More sharing options...
crazyd Posted April 3, 2013 Author Report Share Posted April 3, 2013 It was the 15A IGN fuse! It was badly corroded on the blades. Haven't seen a fuse do that before - so glad it wasn't the wiring! Replaced it and rechecked, full battery voltage. Started it up and the compressor started immediately. It's charging out there now. Thanks guys! Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 3, 2013 Report Share Posted April 3, 2013 Glad you did not have a major problem after all.... Now that you are charging, which refrigerant are you using? If it's 134A the system will charge to a max amount approx 10% less than the system would use in it was filled with R12. Don't over fill the system, it holds 2.25lbs R12, also keep in mind that this is a variable displacement compressor...it does NOT cycle, so don't expect the system to cycle in & out. Quote Link to comment Share on other sites More sharing options...
crazyd Posted April 3, 2013 Author Report Share Posted April 3, 2013 This car came from Phoenix and had already been converted to R-134a, so I've been filling with that. I pretty much charge it till I get to about 40F at the vents and call it done. It's usually around 24-30oz (2 - 2.5 12oz cans). Never knew it was a variable displacement compressor, that explains why it doesn't behave like my Fieros do. Quote Link to comment Share on other sites More sharing options...
crazyd Posted April 3, 2013 Author Report Share Posted April 3, 2013 (edited) Running perfectly (the black outer line is for R134a): Edited April 3, 2013 by crazyd Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 3, 2013 Report Share Posted April 3, 2013 Because the system uses a variable displacement compressor there is very little system *overhead* room that a conventional fixed displacement (that cycles) compressor system has available. One needs to pay attention to the volume they are allowing into the system seeing as the compressor is constantly active. Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 3, 2013 Report Share Posted April 3, 2013 Running perfectly: What outside temp conditions are there right now? That high side reading is Low, it should be up to approx 150lbs, low side looks good at 28lbs. (again depending on the ambient there right now) Quote Link to comment Share on other sites More sharing options...
crazyd Posted April 3, 2013 Author Report Share Posted April 3, 2013 It's only about 54F here right now, too cold for much of a reading. I'm not expecting it to be acting completely normal this time of year. Maybe when we get a summer heat wave in July at around 80F the high side pressure will come up where it's supposed to be. Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 3, 2013 Report Share Posted April 3, 2013 (edited) What I'm seeing there right now is no pressure differential between the low & high side, they're both at 28lbs. The high side should never be as low as the low side except when the system is at rest. (approx 90lbs.) *****I'll get out the manual & take a pic to let you see what the ideal charge pressures on both sides are so you have a good source to charge the system up to. Edited April 3, 2013 by 55trucker Quote Link to comment Share on other sites More sharing options...
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