I just finnished converting my AC to R-134 and found my compressor has a big leak at the rear. It was coming from the high pressure cutoff "red" switch.

I replaced the switch (Discount Auto Parts, $14.99) and new O ring. But the leak persists, although a little slower. I removed the switch to check the O ring seating. It was fine and I replaced the switch again. Still a slow leak.

I inspected the mounting hole with a dental mirror as best I could. I didn't see any damage or debris. I'm hopping that the leak will slowly lubricate the O ring and it will seal itself. Am I just being too hopefull?

The system was completely empty when I bought the car and I evacuated the system for 1.5 hours before charging with R-134.

you sure there's not more than one leak? You sure you didn't bugger the O ring installing the new switch. You should have oiled the ring before pushing it in the hole. (You have to use AC oil to oil the ring. The same oil that's in the system.)

If you didn't oil the ring before instaling then the ring may have a tear/cut on it. Even a tiny cut is all it takes to ruin it in this application.

If the O ring is good, then you'll need to drop the compressor off the brackets so you can inspect the hole better.

Well, I replaced the o ring and switch again. Used plenty of oil this time. But it still leaks.

The wiring to the switch is questionable. If the high pressure cutoff switch is not making contact with the wiring, could this allow the compressor to over pressurize the system and start leaking? But the leak starts immediately and I think there is a high pressure relief valve which would vent before a leak started.

are you certain it's the switch hole?

hanging a gauge on the system will tell you really quick if it's a pressure problem. If you put in the same amount of 134 as R12 then it's likely over charged. you usually only use enough 134 to = 80-85% of the R12 charge.

if it is still the switch you'll have to drop out the compressor. at least from the brackets. and inspect the hole. it's probably got a score or piting in it.

[This message has been edited by theogre (edited 02-23-2000).]

As for the charge amount, I used two 12oz cans of R-134 followed by a can of oil (8oz + 4oz of R-134). Thats only 28oz R-134 total.

After replacing the switch, twice, I recharged with two cans (24oz). Just enough to trigger the compressor. And it still leaked. I assume once the system is opened, all the freon vaporizes and is gone so I'm starting from zero, except for the oil.

I thought about damage to the mounting hole for the switch but how did it get damaged in the first place? What would damage it? There are no moving parts and the switch is not removed and replaced on a regular basis.

the back of the comressor is aluminum as I recall. Aluminum Oxide is very hard. One decent size particle of it would easily score the hole. Likely if that did happen that it was when you pulled the original switch.

You are bubble testing this? not doing it by feel. If you do it by feel the leak could be something line a hose near by as well, and it's just blowing across the switch area...

Did you replace the seals for the hoses? You should do that anyway. 134 tends to operate with more highside pressure. If the high side hose seal is funky, which it likely is......

The pressure switch was leaking before I replaced it. I could actually see the oil bubbling out around the switch (I already had the car lifted so I could observe the compressor engaging when I first filled the system).

But even if there was some minor scoring or pitting, the O-ring should still seal these imperfections. I am almost positive that the O-ring has been correctly seated

There was a small hole in the o-ring groove. How it got there I havn't a clue. I used some J&B Weld to plug it up. I think it might work. However, when I went to re-charge the system, the compressor starts making a loud squealing noise when it engages, almost like a slipping belt.

I did evacuate the system with a vaccum pump for about 45 min. Since the oil travels throughout the system with the refrigerant, is it possible that the oil was evacuated as well? It doen't evaporate at sea-level pressure but what about at 25-30 psi of vaccum? I don't want to over fill the system with oil. Can this damage it?

since you shot first and asked questions later it's hard to say what some of your problem is.

You really need to get some gauges on this thing before you hurt yourself. Over charged AC can rupture in a number of nasty ways. The gauge will also help determin if the Orifice is blocked.

You really should have replaced the AC/Dryer and orifice tube. Especially since the system was already dry.

The AC oil should be installed in a particular way. ((As I recall 2 ounces in the compressor the rest in the AC/dryer))you should also have drained the old mineral oil out before replacing R12 with 134. So basically the system is probably over oiled as it is. The mineral oil will likely settle into all the low places in the system mostly in the Accum/dryer and the compressor wells. Mineral oil won't circulate with the 134.

Just how much over oiled a system can be without damaging it depends on a bunch of things. Just how over oiled you are only god knows. depends on how much mineral was in the thing to start with.

probly is the belt, the Fiero AC setup sucks. could be a bad compressor. could be blocked orifice driving up high side pressure.

AC Vacuum is not measured in PSI.... It's Inches Murcury. 30 inches is considered Absolute vacuum. ((Just for kicks 30 inches of vacuum = either 0 PSI or -14 PSI depending on the method used.))The vacuum will not vaporise any type of refer oil. The vacuum is strictly to pull out the water.

The reason you have to hold the vacuum for a long time is that as the water comes out the temperature drops. You either have to pull even more vacuum or wait untill the system warms back up. Gennerally an AC system is only considered totally pulled down when you can hold 29+ inches on it. If the vac is climbing as soon as the pump valve is shut then either you are still boiling water or you have a leak. Since the system was screwedup and leaking and you didn't replace the ACC/dryer you could have a hell of allot of water in it. PAG and Ester oils love to drink even more than mineral does. If there is a half a drop in there the PAG and Ester will drink it, and won't easily let go of it.

Ogre,

I think it is the belt thats slipping. The compressor is still turning when the squealing starts. Only does it on and off when I'm driving. Never when the car's sitting still, unless I rev the engine a few times. The belt looks like it's "jumping" a bit so I guess it's loose and slipping.

The problem is how to adjust the belt. I got the lower bracket loose but can't seem to reach the upper bolts. The Haynes manual doesn't address this. Do you have any tricks for adjusting the compressor belt.

Other than that, the AC cools very nicely (40' at the vents) and the compressor leak appears to be fixed. I charged with about 26-28 oz of R-134. I'm hesitant to add another can because I don't want to go over 85% and it seems to be cooling fine now. I know there is a high pressure relief valve. Is this set to maintain the correct system pressure or only vent at much higher, dangerous pressures?

As I stated in another thread I got a $10 R134A pressure gage at Pep Boys -takes all the guessing out of charge weights. You can also use it to check for blocked oriface tube. Real handy gadget.

the relief valve is a safety device only. You absolutely must use a gauge to check system pressure.

As far as tightening the belt..... if it's been slipped it must be replaced.

there is a belt tightening tool someone got, i think, from J.C. Whitless or Pep boys. makes tightening the belt easier.

you have to loosen the bolts.... no, there isn't an easy way I know of.

I tighten the one on my 85SE v-6 from underneath. It helps to remove the horizontal metal heat shield that is attached to the cradle just underneath the a/c compressor. You'll see an oblong hole (I think) for inserting a prybar to lever tho pulley tight. I don't think it is absolutely necessary to loosen the top bolts.

It also helps to remove the RR tire and fold back the black rebber splash guard. Then you can look right at the compressor.

The belt tightening device from JC Whitney works great. I believe I've seen it at AutoZone also.

Good luck,

Carroll

Well, I'm heading out of town this weekend.

I'll look for a Pep Boys for the guage. Pull the tire to get at the upper compressor bolts. Replace the belt.

Hopefully my next post will be all smiles. Thanks for all the info

I'm back. Got a guage from PEP BOYS. But no idea as to what numbers I should be looking for. Should the A/C be on or off when I hook the guage up and what reading or range should I observe?

Also, how often should the compressor cycle?

Sounds like somebody swiped the instruction sheet from the gage. I had to look at 5 gages before I found one with the inst. intact. I'll e-mail you a copy.

compressor cycling time depends on charge, temp, and comressor rpm. there's no real rule for it.

Got your e-mail Phil. Thanks. I'll be checking everything and replacing the belt this weekend but it seems to be working ok.

Ogre, it cycles about every 10-20 seconds. Probably OK but seems it would be a pretty big "shock" everytime the clutch engages.

Cycling that quickly usually means a under charge. Now with your gage and instruction you will know for sure.BTW sorry about the size of the scan

No problem on the scan. I found the instructions hidden behind the guage. Small and folded up. Still trying to figure out how to install the high side service port. Currently the low side reads 40 psi and drops to about 20 when the compressor cycles on. Probably not right. Its plenty cold but I'd guess that the freon is low. But I'd like to check the high side as well before adding more R-134.

Where would the orifice or reed valve be located if it needs checking or cleaning?

The oriface tube is inside the short length of metal tubing directly below the acc/dryer. For the high pressure side you most likely have to buy an adapter($3 I think). GM is an odd ball size.

legally, as well as for safety, the fittings must all be converted to R-134a quick connect fittings. You will need the corect gauge adaptors if any after that. The fittings keep anyone from ever installing R12 on top of the R134. Unused R12 ports should be permanetly sealed.

For the same reasons there is a labling requirement. The lable should be placed near one of the AC fittings if posible. On that lable it is a very good idea to list what oil was used. You should not mix the 2 R134 oil types.

Ogre
If you get the R134 gage it will only fit on the 134 fittings. The replacement 134 high side adapters come in a couple of different sizes(GM and the rest of the world).