A/C Issues...

[scmguru]

I posted this to ACKits but figured someone here may have a bit of P-Car insight on the matter..

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I'm trying to get my A/C sorted out on a 1986 Porsche 930 and am running into some problems.

This system was converted from R12 to R134 a few years back.

It stopped working (blew warm air) in January and required a new expansion valve and a new receiver drier because they were "plugged up" per the shop.

System capacity is listed is 48oz of R12.

I'm currently having the following problem:

If the A/C shop pumps down the system and fills it with the "proper" R134 charge (40oz per the shop), I am getting warm vent temps.

I've listed the corresponding vent temps/pressures below with various differen't charges, all at about 70 degree average ambient temp.

1. 40oz R134 charge- Idle Low Pressure 55lb, High Pressure 260- 61 degree freeway (3000RPM) temp, 65-67 degree idle vent temp.

2. 30oz R134 charge- Idle Low pressure 45lb, High Pressure 240- 61 degree freeway (3000RPM) temp, 65-67 degree idle vent temp.

2. 16oz R134 charge- Idle Low Pressure 25lb, High Pressure 225- 48 degree freeway (3000RPM) temp, 61 degree idle vent temp

I know I've been able to get vent temps in the mid 40's and I'm trying to understand why the system is showing high low side pressures and normal to slightly elevated high side pressures.

I keep getting different answers from the A/C Techs. One said I need a new compressor, the other said the system is warm because of R134 and wanted me to go back to R12..

Is it possible the newly installed expansion valve is adjusted for R12 and not R134?

Thanks for any insight.

Mike

[86 911 Targa]

Mike,

If you had good system performance after the transition from R-12 to R-134 then
here is the question.

Was the transition performed during your ownership of the car?

Why was it performed?

And:

Was the transition performed properly?

I'm not at all familiar with R-12 to R-134 transitions.

However, it has been noted that improperly performed transition will, over time
degrade system performance.

Indications are, based upon your low side high pressure that there is a partial
blockage either at the dryer or the expansion valve.

The expansion valve has no moving parts and function basicly as a high pressure orifice.

At 2000 rpm's, the ratio of high to low side should be about 10:1 for the ambient temperature you indicated.

Our '86 (R12) indicates 22 Low and 250 High @ 2000 rpm's on a 75F day.

Check my other posts RE: A/C and high oil temp issues.

Send me an Email for further discussion as there are several variables in your concerns.

Good luck,

Gerry