CaminoSS

First of all, guys thank you for all your help.

1990 Model with automatic trans

My A/C compressor cuts out and cycles on and off when I come to a stop. Of course then the unit blows out hot air rather than the nice cold stuff.

When the car starts to move again, the compressor engages and the AC blows cold again.

I drained the R12 an changed over to 134. There is enough freon in the system. When the guage was on the lines and the compressor would cycle on and off, it was shooting up in pressure.

Is there a pressure switch that might not be working properly and causing the unit to do this when the car is at idle? Is the oriface tube possibly clogged?

And lastly, when the compressor cycles on and off, there is a puff of freon and oil that comes off the top of the compressor right behind the wiring harness. Is that a pressure relief or do I have an issue there?

Again, thank you guys.

silver86

A puff is not normal...you have an issure there. The system is completely contained. Typically, rapid cycling of the compressor cycle is caused by low freon levels, which it appears you have since you're venting freon.

CaminoSS

Freon level is not the issue. Like I said I just drained and re-filled the system.

I am trying to figure out why this thing is jumping up in pressure and venting.

Thank you for your response though.

toptechx6

Are you sure it isn't overcharged, are the fans running? That would explain the venting of freon and it may be tripping the high pressure switch cutting off the compressor. Pressure in the system will increase as airflow decreases, caused by slowing down.

Hooked on Vettes

On a 90 there is a ac high pressure switch that turns off the compressor when the high side pressure exceeds 430psi.

The ECM turns on the secondary fan when the high side pressure exceeds 190 psi.

The venting you mention is not normal.

Did you have a problem before you converted to R134A?

shop14

your system seems to be overcharged or you may have a restriction in the system creating high pressure therefore the purge and the cycle.

draakarmaul

did you hang gauges? what about the condenser? is it clean?

DaSouthWon

did you change the oil in the compressor and drier when you did the swap or just refill the old system with 134.

CaminoSS

To answer all the questions....

Yes the proble existed before converting to 134. That was why I did the conversion, the R12 was venting out at the top of the compressor.

The system was changed over properly, drained, and flushed. Then filled.

I do not think the system is overcharged. I only used 3 cans of freon.

I not certain that both fans are kicking on. I have not been able to throughly check the fans. I will check that in a few minutes.

Again guys, thank you. Any suggestions are helpful. I hate to pay someone to do something I should be able to fix myself.

If all else fails.....use a bigger hammer!

89 Bob L

You had indicated that you did the job yourself? If so, you didn't mention that you had vacumed the system or added oil? This may be your problem. In order to properly convert from r-12 to r-134 you have to vacate all of the r-12. You must then remove the a/c line from the compressor (change the o-rings while you are at it) then put in some a/c oil (I don't know the exact name). You must then pull vacum the system (pull all of the air out), then install R-134. The conversation should be done by an a/c professional. Hope this helps.