ViribusUnits

OK, here's the deal.

When I purchashed my car last October the a/c was stuck on defrost. Since then I have repaired the vacuum system, and vacuumed it out, and refilled with Freeze 12. (I know, snake oil, but it was cheap.) It was filled to the right pressure for the ambiant temp. There were a few bubbles in the sight glass, so I figured I was good.

Last thrusday, it was hot, almost certainly over 100` F or so. I was stuck in traffic. I had my a/c on. The engine wasn't overheating, the electric fan was going pretty good, just like it's suppost to, and the a/c was blowing rather cold. Cool, right?

Well, then something not so cool happened. I heard a sound like a vacuum leak comeing from the center vent. It only happened when the auto or bi was selected, the two Economey selections resulted in no noise. When the selecter was off, there was no noise.

OK, vacuum leak, right?

Then it got hot, the air comeing out of the vent was ambiant temp, rather warm actualy. Hum... Thats not right. The a/c had it pretty cold too. a short while later I pulled over to the side of the road and poped the hood. The a/c clutch didn't engage. Hum... What could cause that?

Next thing I knew, the vacuum noise quit. I can't make it do it now.

I couldn't find a leak in any of the exposed refergerent pipeing.

Would a break in the seals going to or from the evaporator blow like that, causeing a leak only when the high side is pressured up, and then when I turn it off, stop? Would such a leak sound about like a vacuum leak? and when the freon leaked down to a low enough level, the a/c safty switch shut the clutch down?

Yes, no, mabe?

If this is the case, looks like I'll be joining the R134a sHARK folks.

Thanks.

Mitch Johnson

VU,

Don't know about the sound, but this may be what kept the A/C clutch from engaging.

Antifreeze switch:



hth

MichaelR

Hey, VU...bringing back an old thread. Did you ever figure out what the hissing noise was? I've got the same thing going on. I've taken the console apart, tested all the vac lines, and only found the recirc actuator to be leaking. I've got that taken apart, and have to buy the actuator...but that's still not the noise I'm hearing.

On my '85, the hissing noise starts when I hit the a/c switch, stops when I switch it off. The noise is coming from behind the center vent, possibly from the evap area. I don't believe it is caused by any of the HVAC vac lines. I pulled the black line so that I had no vac anywhere, and I still got the hissing noise.

Did yours turn out to be a refrig leak at the evap?

ViribusUnits

Yes I did. That post is from MANY MANY moons ago.

The noise the freon, as a gas, going through the expanshion valve. The liquid is quiet, the gas is noisy.

If the noise in constant, then it means only gas is going through the evap, constantly. Meaning, the compresser can't compress it enough to make ti a liquid. This means that you don't have enough freon!

So, check for leaks in the system, and add some freon.

Oh, one more thing. Mine turned out to be a shreaded nose seal on the compressor. Basicly, it was old, and the rubber got brittle, and went bye bye. OR wait, maybe that was the time before. That time it was the low pressure a/c hose. The origional hose had been replaced by a barrior type hose by the PO, but the shop that made the hose screwed it up, and the crimp was done wrong and started leaking. One time or the other. I can't rember which was which now. That was alought of work.

MichaelR

Thanks for the info. Perhaps it's time for me to make the switch to R134a, and replace the necessary parts along the way.

Thaddeus

On most car A/C systems, if the system is no longer pressurized with coolant gas, the pump will cut out and no longer run. I don't know about Shark A/c, but it's true of Volvos and other cars. I suspect you have a leak somewhere, and the car is sensing the lack of coolant and refusing to let the pump run.

ViribusUnits

On a hot day, there is a pressure that will allow the compressor to run, but will not beable to condense the freon into a liquid.

Basicly the compressor turns, but there isn't enough freon to do much of anything.

He probably has a leak somewhere, but the sound is just telling him that he doesn't have enough freon.