dnwong

I have not used my A/C on the 86 944 Turbo for 7 years due to loss of freon. The system was converted to R134a a long time ago and not sure if the R12 was removed first.

So, I vacuumed it to 30hg and started to fill with Freon/Oil that had some stop leak.

The low side was at 70 and nothing on the high side.

I read that you can jump the pressure switch to get the compressor to start. So I momentarily jump it while adding freon. I was able to get the high side up 70hg and the low side cycling from 40-80.

I was afraid to short the pressure switch for any length of time. Can I just leave the pressure switch shorted for a while to allow more freon to get sucked into the system?

Sounds like I need more freon...?

Still no cold air yet...

Tiger03447

You might jump out the pressure switch, or you can slip a short jumper under the contacts on the compressor and do it that way too. You'll still have to leave the compressor connected so it can get power. Did you replace the receiver dryer too? Those are only good for about 20 minutes if left unsealed..I would change that out as well before charging. You might get by with a 30 minute-45 minute vacuuming of the system and pressure check (15-30 minutes) additional..before adding the refrigerant...Do not exceed about 150 on the high side (If memory serves correctly). These systems can go well over 450 on a hot day...so it's gotta be tight..did you put any dye in as well? It can be VERY helpful when searching for leaks...hope this helps some.

V2Rocket

low should be 30-40 while compressor on and car idling, high should be 150 or so.
with engine revved up to about 2000rpm low side will fall to 25-30 range.

you may find that you have to go back in and replace o-rings soon.

Spidey944

Your charge level when using R134a will be about 75% of what the R12 capacity is.

If your high side pressure is zero, generally it's because the compressor is not coming on. If your charge level is correct, and it's only putting out 80 on the high side, your compressor is toast.

If you had a restriction in the system, your line pressures would be over 300 with the car @ 2k RPMs or so. Hope this helps.

dnwong

Yep, I never open the system up. Just low on Freon all these years and I don't drive in the summer in the past. So, I should not have to replace dryer.

dnwong

I a Freeze-12 kit that I have never used. Wonder if that would be better than the R134a refrigerant?

Tiger03447

If you have a can of R--12 you have a gold mine in your hand...Goes for 150-225 per can...since you've already converted it over to 134a, keep going with it...no need to back up in the process...If the charge is low, then air has entered into the system..You may top out on the high side before you get cold....since the air and moisture in the system occupies space that would normally be occupied by the refrigerant.

Tiger03447

Since you vacuumed the system already, there is nothing in the system at this point, except the new R134a. You should get an internal temp of about 40-45 degrees at the vent. The engine should be idling with the A/C cooling control on MAX and the blower on high... sounds like you need to add some more to get the high side up to about 150...as you add more, the center part of the compressor will start turning, off and on..as you keep adding refrigerant, it will start staying on longer and longer until it is on all the time. At this point you have enough refrigerant in the system to keep the low pressure switch engaged and you can remove any electrical jumpers, etc...and you should almost be done!

dnwong

I tried to put a second can of freon in. The low side eventually settled around 100 and the high side is at 100. However, when I short the pressure switch, the low side quickly goes up and the low side drops. I do not leave the pressure switch shorted very long as I was afraid the low side would get too high.


Does, this seem right?

Tiger03447

I think that you might have a low side restriction in the system..Time for the shop or to an A/C tech that used to working on P-Cars. Ist there a sight glass on the receiver/drier? Are you seeing bubbles in the glass? If you are seeing bubbles, it would indicate a low charge. At this point the compressor should be able to run by itself and the shorting jumper is not necessary..But it is a moot point if you have to take it to the shop anyway to find out where the restriction might be..let the tech take it from here. These are abnormal readings. Hope this helps some.

dnwong

The sight glass is not really bubbling and the can of Freon; although getting empty ever so slowly, does no feel cold.

PaulD_944S2

In your video it looks like you have the high and low side gauges reversed.

Blue is low side and pressure should go DOWN when revving the engine.
Red is high side and should go UP when revving the engine.

Are you sure you have the hoses connected to the correct manifold ports?

dnwong

Give the man a pickle!!!!!

I double checked and the the PO had the retrofit adapters backwards and the gauges are hookup up backwards.

With the gauges correct, I was able to hold the short long enough to get a reading on the pressures and the a/c is working and cold air in the cabin.

So, with a/c on. Low side is 30 and high is around 200.
with a/c off. Low is around 75-80 and high is around 175.

Not sure if it will settle more if I keep running the engine.

Its 80 degree here. Does those pressure seem right or too high (Based on Tiger's comment above). Do I need bleed off some freon?

Thanks All!!!