SQLGuy

He doesn't know if there's charge in it or not. Adding refrigerant if it's not needed isn't going to help things. Adding too much could rupture hoses. Adding R12 if it's been converted (incorrectly, like my GTS was when I got it) to 134a would be disastrous.

Checking whether there's continuity across the pressure switch would be a much easier way to find whether low charge is a factor or not. In most other cars, I'd agree that low charge would be my first suspiscion. In these cars, the head unit relay would be my first suspect.

MainePorsche

After sitting for years I would evacuate the refrigerant, the same as I would do for the gas, oil, etc... Charge the system appropriately, and then proceed systematically with the knowledge that an uncharged system is now excluded. I wouldn't go to the 'usual suspects' first without first tending to this. I think all unknown variables need to be made known before undertaking an algorithmic systematic approach. A known charged system would be required to begin.

SMTCapeCod

Yes, pls! Count me in!
Maybe we can try to put a snowcap on short hill?

Randy V

I can pretty much guarantee that his system needs a freon charge after sitting all these years.

That's all.

SQLGuy

If it needs a charge because it's been sitting, then it also need a bunch of O-rings and maybe other parts replaced to fix the leak.

BTW, the 1150g number quoted earlier is only with rear A/C. It's 950g without. Both values are for R12. R134a is lighter, IIRC.

MainePorsche

R12 - 950gms; 1150gms with rear.
R134 - 860gms; 1050gms with rear.

s4bill

How can you determine if the system has been converted from R12?

If it still an R12 system, can you still get R12 refrigerant?

GeorgeM

If it was done correctly, you'll have R134 bayonet style fittings on the hi and low ports vice the R12 style screw-ons.

You can still get R12, and it's not as much of a difference in cost than R134 as it used to be... i.e. the gap appears to be closing. Check Craigslist and don't pay more than $20/can. You may have to show a license, so go online and take the test and get your MVAC 609 certification for $25. Then you can buy it legally without having to promise to resell it only.

Lot's of back and forth about R12 vs R134, but the sytem was designed to work on R12, and (IMHO) generally works best that way.

Randy V

The fitting ports wil have been changed to accept the 134a adaptor.

Payload

If any work has been done in the center console, is could just be a loose connection to the A/C switch. I was working behind my center console several weeks ago and had it pulled out 5-6 inches from the dash. After putting it back together, the A/C wasn't working. Got it back apart this weekend and realized that the problem was that the connection behind the A/C button had popped off when I pulled the console backwards. You can check this without lifting the console by removing the left carpet panel under the console (2 screws) and feeling around behind the A/C button (at least on an 86 - not sure what the climate control config is on your model.)

-Matt

SQLGuy

Hopefully.

My GTS came with R134 in it, but no conversion label and no retrofit adapters. Fortunately, I was able to get the information about the fact the it had been "converted" from the PO.

SQLGuy

You can also check this by setting to Def, which should engage the A/C clutch regardless of whether the button is pressed (or even connected).

s4bill

Is there a diagram that shows the AC unit system?

How do you tell which is the high and which is the low port?

I magine this is based on location in relation to the other AC components?

Bilal928S4

Low port is under the upper radiator hose for the S4/GT. The high port is right above the filter/dryer in the front.
Hope that helps.

mickster

Those numbers appear high.

R134a should be 80-85% of R12 for refill.

760g/920g--and that's dependent on model year; after 88 I believe it goes down in capacity.

Otherwise you may blow the system...ask me how I know...