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TxBuicks

Buick Rescue: 1991 Park Avenue: A/C Issues

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I am trying to rescue another neglected Buick from an old neighbor of mine. He bought a 1991 Park Avenue new and has let it sit for several years while he drove his modern cars. It runs great, and the leather interior is almost perfect. I have everything fixed and ready to sell, except for the A/C. Not only does it blow through the defroster vents all of the time, but the compressor never kicks on. If I try to put it on Cold air, it immediately goes to 'Econ' and starts blowing outside air. It originally had the old Freon system but the owner had it converted to 134 several years ago. The Freon level seems to be ok, as I tried to add Freon and the high pressure level was in the operational range. According to the past owner, he was driving it one morning and turned the defroster on to clear dew from the windshield and it never went back to blowing out of the normal A/C vents afterwards. But he swears it was blowing cold air up until I took possession. I read somewhere that disconnecting the battery for several minutes will reset any computer related problem. I tried disconnecting the negative terminal for a few hours, and there was no change. I am thinking of buying a shop manual for it but do not want to spend $50 if I don't have to, especially when I want to turn it over cheaply to someone who needs transportation. I am trying to keep it below $1,200.

So, my questions are:

1. How would you continue to diagnose the cause of the A/C compressor not coming on?

2. Do you think the defroster issue is related in some way, or do you think it is two separate issues?

3. Could it be the control panel?

Any suggestions would be appreciated. I'm just trying to get another Buick back on the road. I have two people interested in it now but they won't have it without A/C. It is summer in Texas, so I don't blame them.

Thanks.

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Roy, with the a/c on, check for voltage at the a/c clutch first. If voltage at the clutch, then maybe all it needs is a clutch which can usually be replaced separately. If not, see if the clutch will engage and it will cool with a jumper at the connection (not a fix, but may isolate the problem further).

Willie

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Controller? Do you mean the control panel in the dash with all the buttons? No, I don't know how to check that. That is my biggest fear, because they don't look like they are repairable, only replaceable. I feel lost without a shop manual. A shop manual is usually the very first thing I acquire when working on a Buick I haven't owned before. The manual I have for a 1991 Roadmaster is not the same. But I'm hoping I can fix it without one, with your help, of course.

Edited by TxBuicks (see edit history)

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I believe the Park ave was a little different than the Reattas but we have seen the dash push button not work. Push the button and you cannot change the settings....I don't think that is what you are saying.

The next step is to find the underhood relay box and locate the a/c relay. The ECM gives that relay ground to activate the relay and turn on the compressor clutch. Once you find the relay, you can jumper the pins and force the clutch to turn on.... if that works the problem is either one of the HI-LOW pressure or temp sensors not sending the ECM the info it wants or the ECM itself. A service manual really help track down the problem.

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Well, everything I was able to check seemed ok. It keeps throwing an error code 66 that indicates low pressure in the compressor but I couldn't see anything wrong with the low pressure switch, and it seemed to be full on freon. So, I took it to a mechanic. He tested everything and told me it is all in working condition, but something is telling the system it is low on freon, and shutting it down. He said it could be the ECM, the A/C controller, or even the control panel. He said it would take him another 2-3 hours of diagnostics at $90 per hour to determine the cause of the errant signal, then there will be the cost of replacing the broken part. I can probably replace whatever module is broke if he can tell me what it is. At this point I am thinking it is too expensive to fix. My point in all of this was to have a cheap car to sell to someone who needs it, but putting more money in it defeats that. The car has only 125,000 miles on it and runs great. I haven't paid for it yet. I told the original owner I would sell it for $1,000 to someone by the end of August or buy it myself. He was going to donate it to a charity for a write-off. I guess I can explain the situation to him and just give it back. Any thoughts?

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How are the sub rails around the engine and rear axle? I know some one who needs a car and ac is not a big issue if the car is not rusted inthose areas any pictures of the car Roy?

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John,

The car has been in Arlington, Texas since new. It won't have any rust. Faded paint, yes, but no rust.

I've seen it, but that was a few years ago.

Pete Phillips

Edited by Pete Phillips (see edit history)

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I don't have a Park Avenue manual but referring to the '91 Riviera/Reatta manual the low pressure switch opens at 8 psi and shuts off the 12v to the compressor relay coil. It is also a signal to the BCM.

Working correctly it is ON ...... you should be able to override or eliminate the low pressure switch by unplugging the connection and putting a jumper into the cable connector contacts. If that doesn't work, it is not the low pressure switch itself.

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After talking to a mechanic friend in Columbus, Ohio, he has me convinced it is the orifice inside the system. His theory is that since it runs for a few minutes, all of the pressures start off ok. But if the orifice is plugged, the high pressure end will suck faster than the low pressure end and after a few minutes the low pressure will drop to the point of the switch taking over and shutting it down. Makes since to me. He said if I could hook it up to gauges and watch it run, you will see the low pressure drop until it cuts off. But if the pressures are all ok when it shuts off, then it is something else telling it falsely. But I don't have gauges to check it out myself. However, to change the orifice, all of the freon has to be taken out of the system, then put back in after the orifice is changed out. I don't have to equipment to do that, and to have someone else do it would cost me more than I am willing to spend on the car. The deal was I take the car and find a buyer for $1,000. The original owner expects to get $1,000. I just spent $100 getting the A/C diagnosed. If I spend another $500 getting the A/C fixed, I will have to sell it for $1,600, or take a loss for being a nice guy and trying to save another Buick. I really do think this will be a good car for basic transportation for some time to come. I think my next attempt will be to approach the original owner and see if he will split the cost of repairing the A/C. If so, I will probably do it, and take a little loss on it.

Pete is correct in his assessment of the car. There is absolutely no rust on the car, and the red leather interior is almost perfect, other than the headliner being held up with stick pins. The trunk is perfect. However, being in Texas and sitting outside, all horizontal surfaces are badly faded. I figure a $250 Maaco paint job would take care of that. At only 125,000 miles, the 3.8 Liter engine runs great. I will post some pictures as soon as I get a chance, within the next few days.

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....and after a few minutes the low pressure will drop to the point of the switch taking over and shutting it down.

It acts like that with low refrigerant charge also.

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I located a set of A/C gauges at a local pawn shop for a decent price. I will hook those up and watch what is actually happening. I can't stand all of the speculations without the correct diagnosis. Probably won't have time until this weekend, though.

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I talked to the original owner and he has agreed to split the cost of the A/C repair with me. Actually, he said he will now take $750 for the car. What a nice guy. I truly believe he did not know of the A/C problems when he agreed to give me the car to sell. He just wants to see it go to a good home. I will definitely do what I can to get the A/C fixed and ready to sell. I will post pictures as soon as I can.

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