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AC and gas gauge issues on 1992 olds 88
08-01-2011, 12:26 AM
Post: #1
AC and gas gauge issues on 1992 olds 88
The AC compressor will not engage on my recently acquired 1992 olds 88 regency. The climate control diagnostic code shows 48, which I know means "long term freon loss". What I don't know is what that actually means. The car sat for little over a year with the battery disconnected. I was told the AC worked fine before my ownership and it probably just needed freon. I had this checked and there is plenty of freon in it. So, what do I check next? The blower works fine except for the fact that it blows hot air.

Second issue, the gas gauge doesn't work and I'm not good at doing the Urkle thing so, how hard is this to fix? I'm not a trained mechanic by no means and would appreciate any advice. Thanks
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08-01-2011, 10:10 AM
Post: #2
RE: AC and gas gauge issues on 1992 olds 88
If the AC doesn't work then how would they know if there's plenty of freon in the system? What I am driving at is in order to know if the system is properly charged someone must put a set of gauges on there and at least done something temporary to get the compressor running long enough to compare the gauge readings. Anything besides this method is just guessing. That said, this system uses R-12, which is no longer available at a reasonable price. Since the car has been sitting and is 20 years old you are looking at a repair that will be worth a few phone calls to compare prices for a conversion to R-134a.

Oh, forgot to mention that freon can leak from the system on a car that's just sitting around, especially an older car.

As for the gas gauge, the problem could be at the tank end or the dash end and I would need to get into a detailed explanation to go farther than to say there's a ground wire along the harness in back that you may want to check for rusty connections. The other easy check would be to look at the fuses.

Let us know how you make out.
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08-01-2011, 01:07 PM
Post: #3
RE: AC and gas gauge issues on 1992 olds 88
Thanks for responding to my thread so quickly! First of all, I forgot to include that it has been converted over to R-134a. I had bought a can of the refrigerant with a gauge on it and that's when I first noticed the compressor wasn't engaging. I hooked up the gauge to check the compression and it read that it was overcharged. I had no clue you couldn't check the system unless the compressor was engaged. When I took it in to get the inspection, I mentioned to the mechanic what I did and he checked it with his gauge and said it had plenty of pressure (freon). Today, I decided to go out and check the fuses for the gas gauge and decided to turn on the AC one more time and the compressor engaged but does not stay on. In fact, it continuously comes on and then goes off again. Isn't this an indicator that the freon is low? Will I get accurate reading if I check it again?

Thanks
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08-01-2011, 09:28 PM (This post was last modified: 08-01-2011 09:29 PM by Rupe.)
Post: #4
RE: AC and gas gauge issues on 1992 olds 88
Typically this "short cycle" is an indication of an under charged system, although using only a single gauge is not the best way to see things. OTOH, if that's all you have then it will have to do for the moment.

Here's what I would do....

Over closer to the heater / AC case by the firewall is a silver thing about the size of a quart water bottle with the larger AC pipes connected. On the side of that there's a pressure switch and it's job is to turn the system off if the pressure is too low. (either too cold outside or under charged) It's purpose is due to the fact that low flow within the system also equals low lubrication. IOW, the lube oil for the compressor circulates with the freon. See where this is headed?

For a short test or during charging you can remove that plug on the low presure switch and jump it with a paper clip so the compressor will continue to run despite the pressure drop then you can see where the pressure stabilizes after a minute or so. Typically a good switch will go open circuit between 10 - 20 PSI, and this is too low for proper function. I'm guessing you will need to add 1 or 2 cans of R-134a to reach the right pressure. Figure somewhere around 45 - 50 PSI at idle and maybe 35 - 40 PSI at fast idle. DO NOT over fill the system. There's a tag on the AC case with the correct charge listed in pounds and you will have to do some math to convert that to ounces because the newer stuff comes in 10 - 12 ounce cans. Guessing you are maybe half empty at the moment.

Now, a little theory so you have a better understanding....

The newer stuff (R-134a) has a smaller molicule size than R-12 so if there are any small leaks it will leak out faster. If you see any crud build up around the comp pulley that's a clue to where it's going. Most other locations for leaks will not be found by the naked eye. What I;m driving at is the old stuff might have stayed in the system for years but due to wear and the change of refrigerant it may only last a season or two.

Most parts stores sell cans of "seal conditioner" which may say "stop leak" on the outside. Depending on the size of the can there may be several ounces of 134a in there as well (read the lable) so consider this as part of the refill if you go that route. Do the math and do not over fill the system!

BTW, don't forget to remove the paper clip!

Let us know how you make out.
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08-03-2011, 01:53 AM
Post: #5
RE: AC and gas gauge issues on 1992 olds 88
I jump started the low pressure switch this morning and the compressor engaged without any issues. I also noticed the crud built up on the compressor when I was checking the psi reading. The gauge registered between 0 and 15 psi. So, I added the freon (which btw contains a leak sealer) and filled it to the point where it showed "correct refrigerant charge" on the gauge it came with. This was only 35 psi though and it didn't even use half of the can (16 oz refrigerant/3oz leak sealer). I imagine the gauge is a cheap one plus, it also states the outside temp can affect the reading. Their readings are based on 75-85 deg temps and when I put it in this morning it was around 88 degrees. Once the freon was added I immediately noticed the air blowing out of the vents was cold. Of course, when I left work this afternoon the temp was 109 so the air coming out of the vents no longer felt as cold as it did this morning! I know this was due to the high temperature plus the blower motors on these older vehicles aren't as powerful as they are on newer ones. Is it even possible to replace the blower motor with a more powerful one?

I plan on checking the psi reading again on Friday (next day off) and will let you know if there is any change. I may just take it to the shop so I can get an accurate reading. I again thank you for your help. Your instructions were easy enough for even me to follow and I normally need pics as well!

As far as the gas gauge is concerned, I'll check the fuses and ground wire but that's about all I really feel comfortable doing. If neither one of these is the culprit, I'll take it to a mechanic. Should I also test the relay for the fuel pump?
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08-03-2011, 10:31 AM
Post: #6
RE: AC and gas gauge issues on 1992 olds 88
The relay for the fuel pump will not change anything with the dash gauge but on a more positive note at that age some of the gas gauge components cah be had separately rather than like the new style "tank unit" for $500, which includs the fuel pump and the sending unit. (if that's what you need)

Back to the AC.... at temps near 90 or above you are probably looking at closer to 45 - 50 PSI on the low side reading. The low side jives with the interior temp of the car, not the ambient temp outside. The other thing is that R-134a is not as efficient as the old R-12 so you will be off by about 20% of system capacity. Seeing as GM has always had a great (oversized) AC system, most people never notice. OTOH, with those extreme temps any system will be struggling. GM has been using almost the same blowers on their cars for the last 30 years so unless the old one is failing you will probably not gain anything with a replacement unit.

Just a little trivia for those who want to know more about their AC system. The average car's system is roughly 1.5 tons or 18,000 BTU. That's roughly the same as 3 of your household window AC units. Basically the system is trying to cool down a "greenhouse" (all that glass & metal) within 5 minutes. It's a tough job!
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