Tampa 928s

MY AIR SYSTEM IS COMPLETLY DISCHARGED HOW DO I FILL IT IN THIS CONDITION.
The low pressure switch will not allow the compressor to kick on in this condition and the 134 will not fill the system.

Richard S

Jump (by-pass) the switch, fill with R-134, put switch back to normal. Should be Ok for the short period of time it takes you to re-fill. I did it this way.

Rich

Bill Ball

I do what Rich suggests, but....

Did you find and fix the reason for the discharged state?

Did you fully evacuate the system with a suitable vacuum pump?

Tampa 928s

I'm sure it has a leak but I cannot find it till I refill it. The Heater valve was stuck open and I thought that was causing the problem. After fixing that the compressor was not coming on. My son owned this car and he said the air stopped working. He took it to a shop and they said it needed a compressor, r/d and expansion valve for the R-12 conversion. They " I believe" charged it as stated the above. Since I purchsed the car from him I have since found the system empty. this leaves me with putting R-134 in and trying to Id the problem. Is there another way, I do have a sniffer and Vac pump along with gauges.

Bill Ball

Ew, so you're doing R12 to R134 conversion. Well, then it needs the compressor oil drained, system flushed and the drier replaced first.

H2

In what year did Porsche switch from R12 to R134?

H2

dr bob

1993 on the 928. Part way through the model year. They held out as long as they could...

Angel84-928

Tampa928s, I'm interesed in what you come up with. My A/C system is also INOP.

What would be the indications that a Compressor needed to be replace? Besides the obvious seized condition.

SharkSkin

Usually they continue to work until they seize or leak, prompting replacement or re-sealing. You really need to get an appropriate charge of oil & refrigerant in there and observe system behavior with gauges attached to evaluate the condition of the compressor.

griffiths

Tampa,

Assuming you want to find the leak as well as fill the system:
Usually you need some ac tools and some experience to use them.
You could make a few quick visual checks, for signs of ac refrigerant oil collected on dirt on the surface say for the normal things that leak, such as:
the ac hose between the compressor and condenser (at the crimped ferrules)
the compressor (behind the pulley),
the expansion valve (at the hose pipe connections);
The three items above are the most common failures however other components or connections could be a problem as well, such as an evaporator (not common), on a rear air car the evap, exp. valve or the high side hose with the solenoid, and then finally you have the condenser; driers seldom leak.

In order to find "the" leak or "leaks" you would need an ac vacuum pump, a set of ac service gauges and hoses, some refrigerant dye oil, an electronic sniffer, and some refrigerant and method or tool to measure how much you are putting in the system. You would evacuate the system (pulling down a vacuum say for 1 hr), check for gross leaks under vacuum, charge with refrigerant, sniff with an electronic leak detector and check with the black light. All this takes time, equipment and experience does come in handy. This is not to say you could not beg or borrow the equipment, get help from a friend, etc. and have fun learning and doing it.

Have you considered asking a reputable ac shop what it would cost to throw on a set of R134a charge port adapters (if they are not already there), pull a vacuum, add some dye tracer oil, charge the system, and sniff and look for the leak and while they are at quote you the cost to repair aside from the diagnostics?

Again, its fun to DIY but if you dont' have access to right tools its a PITA.

PM if you need more help.

Tampa 928s

I do have a vacuum pump, gauges and a sniffer. The vacumm now goes to -30 thanks to Zuse's help. It drops to 0 with in a few min so I'm going to look for a large leak tomorrow. I will flush and do the R/D once i get it sealed.

griffiths

Tampa,
Assuming you are using the gauge service set correctly, a climb from -30 inhg
to "0" or atmosphere in a mattter of minutes is a VERY major leak "somewhere"; it is not common imo.

Silly question but we gotta ask: can you describe the procedure you used in terms of connecting your services hoses to the system, what valves you opened or closed and when? The only reason I ask is because of your initial post.

And, if you are going to proceed with evacuation and recharge after the repair, has the car been converted to R134a already? What type of refrigerant oil are you using and how much?

Tampa 928s

I had to purchase a hose yesterday to go from and R-12 pump fitting to the center manifold, due to the difference in sizes. I opened both H & L and sides brought it down to -30. When done, closed the valves watched the pressure drop very very slowly. I guess I'll go out and find some 134 with dye I'm sure I'll see it leak out. I'm not really open to keep dumping cans of 134 while I'm trying to id the leak.
Any feedback

Tampa 928s

Leaking expansion valve !

Bill Ball

You could try air pressurizing and do the soapy water thing on all the joints and hose ferules. You might get lucky.