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AC compressor won't kick in during charge


heygibb

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Hello everyone. This place looks a lot different from the last time I was perusing all the great info available here. It's a nice look but I notice all my old links don't work to great tips I had collected over the years.:(

Anyway, I made the leap to 134A freon today but had a little problem. The compressor would not kick in as it should have. My mechanic tried straight wiring the low pressure switch, but that didn't help. He checked the compressor itself and it was fine if powered directly. He checked fuses and relays, both inside the car and under the hood and found nothing blown. His only suggestion, at this point, is to replace the climate control in the dash. I told him I'd come here to find the probable cause of our problem.:D

I've spent a little while reading other posts re AC problems. One recommendation was to unhook the battery temporarily. Another suggestion was to remove the climate control circuit board and clean it w/ contact cleaner. I will try and do both tomorrow. Since I haven't had the AC working in the past 1 1/2 years, I'm open to the contacts needing cleaning. So, gentlemen, am I on the right track?

Thanks for your input. I'd really like to get some cool air blowing through those vents again.

Tim

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Guest Mc_Reatta

Reattas with CRTs can reset the codes via the diagnostic mode. They are BCM codes. 90, 91s apparently need to have the battery disconnected to clear these codes.

Either way have a freon charge hooked up to the system prior to turning the compressor back on or the low pressure code will reset before you get things hooked up and you will be back to where you started and the compressor won't run.

Doubt the keypad is part of this problem, but wouldn't hurt to clean it anyway to prevent other issues.

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Reattas with CRTs can reset the codes via the diagnostic mode. They are BCM codes. 90, 91s apparently need to have the battery disconnected to clear these codes.

Either way have a freon charge hooked up to the system prior to turning the compressor back on or the low pressure code will reset before you get things hooked up and you will be back to where you started and the compressor won't run.

Doubt the keypad is part of this problem, but wouldn't hurt to clean it anyway to prevent other issues.

Thank all for your quick feedback. This is why this site is so tight.

Just so I am on the same page with your suggestion above. when you say "have a freon charge hooked up", do you mean actively charging the system again before turning on the AC? As I understand it, the system was charged, then stopped when the compressor would not start. Chris, my mechanic, troubleshot the electrical source as described above. When he could not get the results he wanted, he released some freon to prevent high pressure from blowing seals. Driving around last night, I turned on the AC just to see if magically things were working. It was cooler air than normal but it wasn't working. Getting back to the point you make. Can I just unhook the battery now myself, then re-connect, and it will work properly? Or do I need to hook back up to the charging system Chris has, then disconnect the battery? I just want to get this right.

Thanks again very much.

Tim

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Please pardon me for butting in on your conversation with McReatta but, I think the ability of the mechanic should be questioned if he is releasing freon to lower pressure in the system before he ever gets the compressor running. If he is reading a gauge connected to the low side port, it is normal for the gauge to read high (maybe up to the maximum gauge reading) without the compressor running. Unless he is forcing freon into the system by using some type of machine I don't see how he could overcharge the system without the compressor ever running. I'm not an expert on A/C systems so maybe I'm wrong.

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Please pardon me for butting in on your conversation with McReatta but, I think the ability of the mechanic should be questioned if he is releasing freon to lower pressure in the system before he ever gets the compressor running. If he is reading a gauge connected to the low side port, it is normal for the gauge to read high (maybe up to the maximum gauge reading) without the compressor running. Unless he is forcing freon into the system by using some type of machine I don't see how he could overcharge the system without the compressor ever running. I'm not an expert on A/C systems so maybe I'm wrong.

You aren't butting in. I welcome input from anyone who knows more than I do. It's possible that I misunderstood what Chris told me. All I know is we evacuated the system and then he either charged or was in the process of charging it when he started to deal w/ the compressor not kicking in. Before I left, I thought he said he was releasing some pressure from it to protect the seals. Like anyone who works on Reattas, which in his case is rarely, if ever, maybe he is learning what's up as I am.

At this point, I was wondering if I disconnected the battery myself, w/out my system being hooked up to his charging machine, would the codes reset and my AC start working. I am going back to see him tomorrow, but if clearing the codes is something I can do, I wanted to go ahead and do it.

Procedure, I guess, is what I want to get right.

Thanks

Tim

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You can't hurt anything by disconnecting the battery to reset the code. If the system is low on freon it will either kick out the compressor again or it will give you a low freon warning and continue to work. I think the compressor will kick out again since the system was not completely filled.

Tim, please add the model of your Reatta, (and any other relative information), to your signature line. It will make it easier for us to help you with answering your questions without repeatedly asking you about the Reatta you own.

Click "User CP" in the menu at the top of this page and scroll down to "Edit Signature"

Thanks!

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I'll do it. Good idea.

for the time being, I have a

1990 Red Reatta Coupe

Tan Interior

No sunroof or 16 way seats

But still going strong at 111k miles. Other than small stuff breaking or wearing out, I don't have much to complain about.

Thanks

Tim

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Guest Mc_Reatta

Ronnie, you are correct.

The computer will latch the compressor off for both a low and very low freon condition. I sometimes have to clear the code several times before I can get enough freon into an evacuated system to keep the computer from setting the code.

I hook up my charging set up before I clear the code so I have the system under some pressure first. Once the code is cleared and the AC is turned on, the compressor should run. The pressure will drop once it starts and it will start to cycle on and off. It is common for the pressure to drop too low to keep the pressure switch turned off or the low temp sensor to trip the code back on and lock out the compressor again. You will know when you don't hear the compressor cycling on and off and the pressure goes up and down when this happens. The low side pressure will go high (to whatever is in the freon container at this point) and stay steady. Just clear the code again and keep going. At some point you will get enough freon in to keep the code from resetting, and then you can optimize the charge.

Jumping the low pressure switch contacts will prevent this from setting a code, but the low temperature sensing circuit can still set a code so this in not a foolproof method.

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With both high and low side gauges connected and monitored, I know that the proper oil is in place, and proper airflow ensured, I see no reason not to jumper 12v to the clutch for initial checkout. Once everything is right then I would clear the codes and connect normally.

YMMV & other weasle words

Edited by padgett (see edit history)
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Guest daveagain909

guys, I am having a similar problem with my 90 convertible, I had a entire new system put in the car last year and all was good, then we hit this colder than normal winter here in North Carolina, then I started having problems getting the AC to come on, At first it would come on and work great then intermittently not come on when restarting car, now I can not get it (the compressor) to come on at all, WE have tried shorting the Low pressure switch and The compressor ingaged for only a second or so, I then disconected the battery and tried again with no engagement at all. My friend says that it is fully charged, he says this by using the gauges, but I am not sure he is getting a good reading because the compressor will not engage. I need some Ideas where to go next? Perhaps it is just low on freon? I am bewildered, I am thinking of going to a mechanic, but when I talk to them I feel sometimes I know about reatta's than they do. Help?

T

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Run a jumper from the battery straight to the compressor clutch and see if the compressor will engage. That eliminates all the electronics. If it still doesn't engage you have a compressor or compressor clutch problem. Otherwise it is an electrical problem.

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Guest Mc_Reatta

daveagain, Is the service AC light on? I assume you checked for AC related trouble codes in the diagnostics and there were none. (EO14, B111, B112, B337, B446 thru 450)

Ronnie's suggestion will determine if the AC clutch is working or not. If it is, then check the fuse, #19 10 amp. (Doubt it's the problem) More likely it is relay J in the underhood relay center or could also be the clutch diode that is in the harness near where it plugs into the AC clutch.

The control of the compressor is via the ECM with input from the BCM, the temp sensors and the low pressure switch. Any problems with these would hopefully set a code.

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Guest daveagain909

mc reatta, The ac light is not on, I checked the fuse and it looks good, I switched the relay with another of same , I did not check codes for I do not know how to ( 1990 convertible)? I will try to hot wire, like ronnie suggested as soon as I can. where exactly is this clutch diode, Is it hard to get at? and where is the temperature sensor, is that the one found near the grill? I want to do what I can before I go to a mechanic.

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Guest Mc_Reatta

Perform Ronnie's suggestion first if you can, it can save some time over checking all the electrical circuits. The diode is in the cable harness leading to the clutch near the plug. You can check it with an ohm meter via the plug. With no power applied, the resistance between the two contacts in the clutch wire plug should be infinite when the probes are inserted one way, and show some reading when they are inserted reversed. If the meter shows a reading near 0 both ways or an infinite reading both ways the diode is bad. However if it is infinite both ways it's not your only problem. While your at it check the resistance from the black wire in the plug to ground. It should be near 0. The green wire leads back to pin 1 of the AC relay socket. Another check you can do is verify that pin 4 of the relay socket shows 12v when the ignition is in run.

The pressure switch and the temp sensors are in the AC lines that run transverse back by the fire wall under the plastic cover. Issues with these should set a trouble code, so I'd pull the codes first.

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Guest daveagain909

can I alos get the codes from one of those plug ins, that throw out the codes they have them at advance auto?

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Just turn the ignition key on. Then press the 'off' and 'temp ^' buttons simultaneously for a few seconds on the climate control unit. The codes will be displayed on your instrument panel where the odometer is usually displayed.

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The diode that is mentioned is just a snubber diode to shunt the current after the field collapses in the electromagnet coil to keep from arcing the relay contacts is it not? If so even if it is open It should not keep the compressor from kicking in. Just a thought ... Terry

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  • 1 month later...
Guest daveagain909

I've been working with a mechanic for 4 weeks now and testing to find problem. Ac has Freon, he can get it to turn on by shorting out, ( I will have to ask him specifically what and where he shorted it out to get compressor to turn on) It gets cold fast, Then one day it just turned on and operated for about 5 minutes then stopped, Any Idea why???. He has traced the circuit all the way back to the ECM, finally telling me that his readings from the ECM say that there was something wrong with one of the readings (30)? We then replaced the ECM with one from Jim Flynn, with no change same bad reading. He is now talking to friends he has that are mechanics at a buick dealer, I do not know what to do? I can get specifics from him If it will help, He is as frustrated as I am. Help?

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I've been working with a mechanic for 4 weeks now and testing to find problem. Ac has Freon, he can get it to turn on by shorting out, ( I will have to ask him specifically what and where he shorted it out to get compressor to turn on) It gets cold fast, Then one day it just turned on and operated for about 5 minutes then stopped, Any Idea why???. He has traced the circuit all the way back to the ECM, finally telling me that his readings from the ECM say that there was something wrong with one of the readings (30)? We then replaced the ECM with one from Jim Flynn, with no change same bad reading. He is now talking to friends he has that are mechanics at a buick dealer, I do not know what to do? I can get specifics from him If it will help, He is as frustrated as I am. Help?
Have you tried unhooking the battery cable for a couple of minutes and reconnecting?

Dave you say: "He has traced the circuit all the way back to the ECM, finally telling me that his readings from the ECM say that there was something wrong with one of the readings (30)? We then replaced the ECM with one from Jim Flynn, with no change same bad reading. " Where are the readings coming from? You say there are no codes. Are you talking about data stored in the ECM? BCM? We need more detailed information.

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The compressor readings are stored in the BCM not the ECM. The low pressure switch can be read at BI08 - it will be HI if a minimum pressure for turn on is sensed.

BD27 and 28 are the high and low refrigerant temperature sensors (can be correlated to pressure) but do not control the initial comperssor turn on.

The compressor on/off command can be seen with one of the symbols in the heater display, I forget which (lots easier with the CRT - says COMP.)

If I were doing one of my cars I would just pressurize the low side to 40-50 psi, then disconnect the battery to reset the codes (cannot clear compressor disable with diagnostics). Check BI08 for HI, and proceed with the charge. YMMV, notary sojack.

Incidently I use less 134A (about 28-30 oz) than 12.

ps apparently the little upper arrow in the car on the heater display indicates the a/c compressor command when in diagnostics. See page 8D-7 in the 90 online service manual.

Edited by padgett (see edit history)
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Guest daveagain909

AC is now fixed had to put in another ECM and then the mechanic and I reset all codes, and disconnected the battery for overnight, Now it is working and I have my fingers crossed that it remains working, so cold yesterday that I had to turn the temperature up and the outside temperature reading was 96 degrees (working well) Thanks for all the help given here, I reaslly appreciate it. On to the next problem that can arise.

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