JHowell37

Questions about A/C for '85.
Is the high side service port the one on the dryer?

There was a sticker under my hood claiming the car had been retrofitted for R-134A several years ago but I don't see a high side fitting.

Compressor clutch won't engage when a/c is switched on from the dash. I know this can happen if it's low on refrigerant. It doesn't seem to want to take any even though the gauge says it's empty. BTW I did get the clutch to engage by hooking up a jumper from the 12 volt post

So any ideas on what it means when it's empty but will not accept any refrigerant?

joejoe

High side is on dryer. You should pull a vacume and check integrity of system. Do not attach to high side as dire consequences can occur.

Bill Ball

High side is beside the drier. Low side is stuck down under the upper radiator hose. The latter is where you should be filling.

So, what pressure readings do you get on the ports? When you jump the compressor, the high certainly will not take any if it already has some charge, if that is where you hooked up your can. Try the low side port and report back.

JHowell37

For some reason the high side didn't have an upgraded service port on it. This is where it gets strange. I picked up a retrofit kit today mainly because it had 3 cans of r-134a plus a new set of service ports. The high side fitting that came with it would not fit onto the fitting on the dryer. The low side fitting would screw onto the high side however. Perhaps there's a reason it never had an upgraded high side fitting.

I actually wound up hooking the can up to both and in neither case would any coolant go into the system. With the compressor jumped and running, they read zero.

I'll go back to the part's store tomorrow, they have a set that contains four fittings (2 high, 2 low) and I'll see if one of them will work. Or I'll just use the other low side fitting and change the hoses for my gauges. The high side is useless for recharging, but IIRC the high side is where you find out where problems are.

The car sat for a few years prior to my ownership. That + the poor condition it was in when I bought it means at a minimum I'm in for a new expansion valve and dryer. Hopefully, my compressor is still good, but I'm not banking on that. I don't think you're supposed to be able to easily turn the compressor over by hand, regardless of its state of charge.

Bill Ball

If it read zero, then you need to evacuate before you charge, as joejoe mentioned. It is likely you have leak. It's possible that the retrofit adapter just came loose and fell off at some point.

JHowell37

I doubt the cap fell off because there was one of the old style protective caps over the r-12 high side fitting. I'm going to have to figure out who to take it to that's not going to gouge me for having a Porsche.

dr bob

There are often issues with the retrofit ports when the R-12 schraeder valves are left in the original charge ports. On some retro fittings, it looks like there's a pin in tthe fitting to depress the old schraeder valve but that's unreliable at best. Conclusion-- pull the old valve cores before installing the retro conectors.


Many later US R-12 cars were equipped with a smaller high-side charge port, intended to prevent accidental charging through that port. Many high-side adapters in common conversion kits are made with the smaller female side to fit over the smaller port on the car. Meanwhile, since the 928 AC was way too complicated for all but factory-trained 928 technicians to service, no need was seen to use those smaller R-12 ports. So shop again for a high-side port adapter that has the correct female thread. That thread size is in fact the same size as the low-side R-12 port. The adapters are pretty common, you just need to get the right one.

The cam-lock style quick-disconnect hose fittings used with R-134a need a good firm squeeze to get them locked onto the port adapters. They must be lined up -perfectly- before they will lock in and open the service valves inside. They can go on just slightly skewed and give you the impression that they are on correctly, but a firm pull on them will show you otherwise. The location of the low-side port makes it a real chore getting the hose attached, especially if the top radiator hose is hot. Gloves protect you r hands but prevent getting the conector on straight and secure.

I chose a right-angle low side port adapter to help with the angle-of-attack problem, but it's still a chore to get it on there just right. Fortunately I've only had to put the gauges on mine a few times since I did the conversion over 9 years ago now. Time flies when you drive a cool car I guess.

Mike Frye

JH,

You might check with John Cho (Tomcat) he's got a real good understanding of these A/C systems and a leak checker, maybe he can give you a hand.