A/C Dead

[dstig1]

'99 V8 AWD, manual AC, R134a

About a year ago the AC was weak and through this forum, I found out the compressor was shot. I had it repaired and all was fine all summer. Now the hot weather comes again and the clutch does not engage in any switch position - dead.

I connected gages - readings were about zero on both high and low side with the engine off (uh oh).
I was able to get the clutch to engage by jumpering the cycling switch. Pressure climbed a few psi on the low side and stayed dead on the high side.

I am guessing I have a system that totally leaked out.

Any other thoughts? And assuming that is it a leak, is it worth adding a can or two of R134ato try to find the leak?

Thanks,
Dave

 

[shamaal]

I connected gages - readings were about zero on both high and low side with the engine off (uh oh).
I was able to get the clutch to engage by jumpering the cycling switch. Pressure climbed a few psi on the low side and stayed dead on the high side.

The refrigerant also carries the oil, don't do this very often. You run the danger of running the compressor witout lubricant.

I am guessing I have a system that totally leaked out.

The compressor disengages at <25 psi and engages at >47 psi. Not engaging and low gauge pressure are pretty good indicators that your refrigerant charge has become one with the ozone.

Any other thoughts? And assuming that is it a leak, is it worth adding a can or two of R134ato try to find the leak?

I'd hook a vacuum pump up to it and see if it draws then holds a vacuum for 15 minutes. Or you could dump a can or two and see if you can pick up a leak. Or you may get lucky and have to only charge once a year.

Good luck

 

[dstig1]

Thanks. I'll see if I can get my hands on a vacuum pump. Otherwise I may try the "add a can or 2 and pray" method.

And I realize that running the compressor "dry" is a bad thing. I was mostly trying to see if it was a bad switch. Only did it for a few seconds. Won't need to do it again.

Thanks again.

 

[dstig1]

Follow-up:

I went and grabbed one of those venturi-style vaccum pumps as I could get it cheap and fast, and pulled vac on the system (only got 21" - not enough for real AC work, but enough to check it out - and yes, I am getting a real vac pump shortly). It lost vac - about an inch in an hour.

I examined every fitting and every square inch of the system looking for oil smudges, damage, anything. Saw only one oil smudge on the cycling pressure switch on the accum. Retightented and looked it over - seemed OK, but couldn't prove it I guess. I also gave a little extra wreching to the fittings that I know they must have touched to replace the comp & accum (gently). No effect.

So where does one start here? I am thinking my only option is tearing the whole system apart, pressure testing the evap and condensor, and replacing every single o-ring. That seems very inefficient. Any other (better) ideas?

The stupid DIY'er question: I saw the R134a cans that included "stop-leak" in them. I do not like leak sealers as I know there are small passages in any system (whether it is cooling, oil, AC...) that might look just like a leak to this voodoo magic goop. Is it as bad an idea as I assume it is? The car has at least 4 more years to go, and AC is absolutely required as it is our long-trip car.

Thanks,
Dave

 

[shamaal]

The most common method in this case is to use a fluorescent dye, a UV light and some freon. You won't need a full charge just enough for pressure to find your leak. A tip - put a rag behind the fitting before you add, there's usually overspray making it difficult to separate a leak from the blow by.

Common leak locations are at the entry and exit points on the condensor, rusted out accumulator (if you have the one wrapped in insulation), the QD fittings themselves (use those caps) and the o'rings at the back of the compressor. Sometimes you can hear the leak also, try slowly turning the compressor and listening.

I have no experience with the Stopleak products.

Good Luck!

 

[gsmaclean]

Follow-up:
The stupid DIY'er question: I saw the R134a cans that included "stop-leak" in them. I do not like leak sealers as I know there are small passages in any system (whether it is cooling, oil, AC...) that might look just like a leak to this voodoo magic goop. Is it as bad an idea as I assume it is? The car has at least 4 more years to go, and AC is absolutely required as it is our long-trip car.

I wouldn't touch the Wal-Mart cans with "stop-leak" in them, for that exact reason. However, there are products out there that circulate normally with the refrigerant, and only solidify and seal once they actually leak out of the system and interact with moisture in the outside air. I had great success with the Cliplight product, I wrote about it in this thread:

http://www.explorerforum.com/forums/showthread.php?t=186402

 

[Brock94]

It sounds like you may have a leak at your pressure sensor since that's where the oil was. I had the same thing happen after I worked on something else and rotated the pressure sensor in the process of removing the connector-- that was enough to cause it to slowly leak. Tightening it won't help though, there's an o-ring in there that you should replace.

Also, if your system is down to 0 psi, why not just replace all the o-rings? It won't take that long and o-rings are pretty cheap. If you don't have, or want to buy, other diagnostic equipment (a sniffer or uv kit), replacing the o-rings would be a good bet.

As far as I know, the pros frown on stop-leak and many will not work on a system if their test shows it contains the stuff-- so you should avoid it if you think you may be taking it into a shop some day. Stop leak can ruin A/C service equipment.