91 Thunderbird Air Conditioner

My AC compressor won't run on my 91 Tbird 3.8L V6 so I went to Autozone to look at the wiring diagrahms after not having found a fuse anywhere in the car for the AC unit. Blower motor works fine and it
seems to switch through various selections just fine but can't get the compressor to kick in.
Anyone familiar with these years in Tbirds that might know where the "AC clutch cycling switch" or "AC cutout relay" might be physically located? Not having found any issues with a 'fuse', I'm looking for one of those components now. TIA
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there is a low pressure switch in the circuit that shuts the compressor clutch power off if the frozen charge gets low to prevent compressor burnout. the odds are 99.9% in favor of a low freon charge.

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wrote:

So is this something then, that would likely be corrected by 'any' shop that does air conditioning or would they have to be familiar with Fords (or Tbirds) and the low pressure switch to presumably run the compressor while they were giving the system a charge? Asking the question in hopes of avoiding the shop or two that ultimately can't help but charge me some bucks for just looking at it. (seems to be quite a few of those these days which drives more consumers to Usenet for pointers... ;-)
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cover wrote:

There is more to it than "giving it a charge". If the refrigerant is low, there is a leak that must be addressed. Shops aren't actually allowed to just "top off" an empty or low system as they are "technically" venting refrigerant into the atmosphere via the leak. If you find a shop that doesn't know about the low side cycling switch, run away quickly. Any shop will charge a diagnostic fee just to "look at it". It takes time, and time is money. Most will roll the charge into the price of the repair if you have then do the work. To expect them to diagnose the system for free is unfair.
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cover wrote:

You don't have run the car at all to pressurize the system with R12. YOUR biggest problem(s) will be find the R12 to buy (without having an EPA exemption certificate), and an install connector. A pressure gauge with the correct fitting is also great to have.
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Sorry pal, but in my humble opinion this is bad advice. If the system lost refrigerant, there is a leak that should be addressed. Even ignoring the legal aspect of dumping it into the atmosphere, considering that today's price of R12 is about equal to that of gold, it would be very unwise to recharge a potentially (if not certainly) leaky system. It may also contain moisture, which needs to be evacuated first. And with a vehicle this old, other repairs, like replacing the dryer/accumulator may be needed. Considering the cost of R12, it may be wise to consider converting the system to R134a at this opportunity. Properly done, this will require flushing etc -- again better done by a pro. And incidentally, the recommended (if not the only) way to charge is with the compressor running.

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Back in the old days when you could buy generic R12 for about .79 a can I had a Ford Granada (second best car I ever had), that had a leaky condenser. In the summer I'd put about a can of Freon a week in that car, and with every fourth can or so I'd add an oil charge. Drove it that way through a couple of North Carolina summers before coughing up the $300 to replace the condenser.
However in these days of the EPA Gestapo if your going to keep the car it makes sense to convert it to R134a. I've got it in one of my Studebakers and it works fine.
Jeff DeWitt
Happy Traveler wrote:

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Jeff DeWitt wrote:

Actually, it makes the most sense to properly seal the system and stay with R-12. It is still available and the price is coming down due to lower demand. If repaired properly, that ~$60 spread out over the years that the system will last is really a minimal factor.
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Happy Traveler wrote:

While what you say is true, I think Sharon Cooke was referring to pressurizing the system to leak test.
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Tom Adkins wrote:

Actually, I was talking about "topping off" the system with R12. Back when I actively worked on cars for myself and other people, and R12 was < $1 a 14 oz can, I'd top off the system using a commercial pressure gauge (after leak testing) to bring the system up to the required low side pressure at 80 F., WITHOUT having the engine running at all. There IS NO "magical check valve" in the system that blocks introduction of refrigerant to the system when it isn't running. As long as the Delta-T pressure of the supply refrigerant is higher than the system pressure, the refrigerant will go into the system; you just require the gauge set to do it that way, with a running check on pressure increases.
BTW, R12 is still available (with an exemption certificate) for maybe $15 a pound, hardly the price of gold. :)
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Sharon Cooke wrote:

I stand corrected. I didn't realize you were talking about that method. Yes, it does work. I will take exception with you about "topping off" an R-12 system though. If the system has a leak, it really doesn't make financial sense unless you have a supply on hand and are doing it yourself. Shops are charging $25-40/lb in my area, and the 1lb cans still generally sell for that price. It seems like a waste. R-12 is much cheaper in #30 cylinders, but not many folks want to spend $300 for one to get $10/lb R-12.
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wrote:

Now you're talking a range where it starts to get spooky. One of my biggest fears has been hearing an overall repair bill of $300 PLUS (I emphasize the plus because I imagine it can climb significantly and quickly above that mark). Another writer mentioned it only being fair to pay the service tech's time for troubleshooting the system although many shops WILL convert (or include) that time toward the repair bill if repairs are done with them. That too is fair enough though, a worst case example might be for the troubleshooting time=$100 and repairs+~$500
I'm a little concerned about this for a couple of reasons, one; I remember years ago as a teenager working in a service station that the 'gravy' jobs and the ones that climbed into the hundreds of dollars THEN were air conditioner related in the summer. two; the last time I visited my GM dealer for a tune up and fuel pump, they shocked the bejayzus out of me when they presented me with an $850 bill that included their 'troubleshooting' time added on with spark plugs at $10ea.
Interestingly enough, over the weekend I found a parts site on the net that offers dummy pulleys for when ACs fail and costly repairs are hoping to be avoided - they've probably been around but I didn't remember seeing those. So... I'm cool with paying a moderate amount towards a repair bill but I think these days too, repair bills cn quickly cross any lines of 'reason' and turn into hard lessons learned if one's not careful with their approach.. ;-) Hence, my visit here. Usenet's a great place...
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cover wrote:

It's not uncommon for an AC repair to easily reach $300. I've done a few already this season that were close to $1K due to crashed compressors. The compressor alone is often $2-300 before installation. On a Mitsu Spyder I did recently, the compressor alone was $450. Aside from a leak at a fitting, AC repair is seldom cheap, and if done on the cheap it often leads to more costly repairs. On your 17 year old T-Bird, a $500 repair bill for the AC isn't out of the question. If you don't fix your AC and the pulley bearing on your compressor is good, the bypass pulley isn't needed. The compressor will just be along for the ride. They are a good option if the pulley bearing has failed.
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though. If the

a supply on

and the 1lb

$300 for one

Phhhttt. $300? That's pocket change for A/C work.
If you are reasonably mechanically minded you can do your own A/C work if your willing to invest maybe $300 in tools, and some time in reading the documentation and understanding it. R12 systems fall into 2 categories: those that use old-style compressors that have an oil resivor (York, etc.) which are worth repairing with R12 (meaning, they will stay fixed) and those that use newer compressor designs, those are absolutely not worth touching with R12 because those compressors are generally all shit and will blow up 2-3 seasons later. Any R12 work requires an EPA certification in order to be able to buy the R12, which costs time and money (not a lot of it) to get, it's not difficult material to understand, though. There's tons of old 10-20 year old R12 cans on Ebay cheap. People hoarded it figuring years later they would make a killing, but underestimated the speed at which R134 would come in, they also didn't forsee the government mandating reclamation which has put a lot of reclaimed R12 on the market.
You can retrofit a R12 system to R134, it's not hard, but it won't cool well unless you replace the condensor with a much larger and more efficient one. If you have space in the body of the vehicle it might be worth doing.
Minimum tooling you need is an electronic leak detector, a vacuum pump, a vacuum guage (which should be part of a manifold guage set) and the various fittings to connect the freon cans. If your working on a charged system you can drive the car to a shop and they can evac the system cheaply. That will help you to be ecology friendly. Years ago we routinely dumped R12 to atmosphere, I wouldn't do that today. As for dumping R134, that's a touchy subject. Legally you must recover it - but what the EPA fails to mention is that all medical asthma inhalers use R134 as the propellant, and there is no restrictions on those, and R134 is used to form bubbles in foam insulation manufacture which dumps millions of tons of it to atmosphere every year, it's the single largest source of R134 vents to the atmosphere. R134 was also selected for it's environmental friendliness, so you might consider the recovery laws on R134 somewhat hypocritical. What I have done is to find a quick-lube place that does R134 charging, tell them there's a crack in an AC line that is leaking and I went and bought a replacement line but just need the system evaced so I can replace it. Lots of times they will evac the system for free, thinking I will come back with the fixed system, of course, once I get the system drawn down I just never come back and I charge it myself. Considering they get money from the refiners for the recovered refrigerant, it's a fair trade. Do this kind of thing on a slow day, of course.

AC work is just tedious, it takes a long time to do it right. That is why it's so expensive. It is really one of those areas where the savings to do it yourself are so large that it is worth doing yourself. Unlike, say, oil changes. With oil changes I have it down to a science I've done them so many times, but still, with oil at $1.50 a quart and the filter at $5, and my vehicles use 5-6 quarts, for me to do the change saves $6 over going to the corner change place when they are having a sale - it's hardly worth DIY it anymore.
Ted
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On Thu, 31 May 2007 02:15:50 -0700, "Ted Mittelstaedt"

If you are only doing one vehicle it's true. But I do all three of my vehicles at the same time. It would take me far longer just to drive them all back and forth to the shop to let them change it then it takes me to just do them all myself. And I use Mobile 1 and run them one year or 12,000 miles. Then I start over with all three at the same time....
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Any shop that does AC work should be familiar with the system and be able to add refrigerant. I believe they bypass the cutout switch while charging the system.
Jeff DeWitt
cover wrote:

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No need to bypass the switch. Just add refrigerant and the pressure will quickly come up enough to close the switch.
Jeff DeWitt wrote:

--
Mike Walsh
West Palm Beach, Florida, U.S.A.
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