A/C Compressor Drag

SVX_MY_BABY · #1 06-16-2015, 09:43 AM

I just had my a/c serviced and installed my original newly rebuilt OEM R12 compressor.

The system didn't cool well, if at all, after the service, so I took the Subaru R134a retrofit instructions to the tech to ensure the system was charged correctly. He evacuated the system and re-did the job as per the attached instructions. He followed them to the letter, but it still doesn't seem to be working. http://www.northursalia.com/techdocs...nt/acretro.pdf

He checked all the lines with a laser type digital thermometer and felt they were the appropriate temperature. As it was a cool day (13 Celsius) is was hard to really determine what was happening as the lowest setting on the a/c control is 18 Celsius.

I did notice that the compressor is cycling fairly frequently and at idle, which is 750 rpm, and when the compressor cuts in the rpm will drop 250 - 300-rpm to the point that the engine almost stumbles. This can't be normal.

Any help appreciated.

huck369 · #2 06-16-2015, 10:07 AM

Maybe the blend door is stuck, and not letting it switch to the cool air......

Blacky · #3 06-16-2015, 10:13 AM

The rpm should rise when the AC kicks in to about 1000 rpm to compensate for the load of the compressor. Also check if the cooling fans engage when the AC is on, they should.

SVX_MY_BABY · #4 06-16-2015, 11:11 AM

Quote:

Originally Posted by Blacky

The rpm should rise when the AC kicks in to about 1000 rpm to compensate for the load of the compressor. Also check if the cooling fans engage when the AC is on, they should.

The cooling fans definitely come on.

But the rpm doesn't rise. It does quickly return to 700 -750 after the compressor cuts in but only after the near stumble.

Ron thanks. Mine worked great after my conversion as well. You'd never be able to tell the a/c was cycling.

Tapani · #5 06-17-2015, 01:59 AM

The svx compressor is of variable displacement type and should not cycle at all under normal conditions.

Dis you overfill the system?

I think you should only fill app 80% if converting an old R12 system to R134a.

I have used only 500g both times.

T

SVX_MY_BABY · #6 06-17-2015, 06:34 AM

Added 1.87 lb. (850g) R-134a as per retrofit sticker on car and directions linked above. Added 200 cc PAG 100 oil.

Tapani · #7 06-17-2015, 07:43 AM

Ok. I would try with less juice... But the 80% is only a general rule of thumb.

The pressure switch will cut the compressor if the pressure is too high.

T

Ron Mummert · #8 06-16-2015, 10:15 AM

Not that this will be of any true help, but 2 weeks ago I had a local mechanic do the R12/R132a conversion, as the '92s good old R12 system finally quit putting out cold air after 23 years of flawless service. All other system components were operating properly. I experienced no changes in drivability, & the A/C is now SO-O-O-O cold, I have to kick the temp to 75 so's not to freeze my knuckles. So....yes, something's not right with yours. Best 'o luck in tracking down the problems.

Ron.