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kalamykid, Shop Owner/ Tech
Category: Classic Car
Satisfied Customers: 4204
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70 Corvette A/C, restoring: evaporator, condensor pressure

Customer Question

70 Corvette A/C, restoring: evaporator, condensor pressure checked; dryer= new dysectant, compressor no noise and worked fine prior to tear down of car. Pulled vac=no leaks. Put in about 2oz ester oil (did not drain comp), 3lbs R-12. All seems to work, but no cold air. Did not tear down expansion or POA. Re-wrapped bulb to evap tube w/insulator tape. Low side press= 1-10 Hg/in, Low side @ compressor iced up @ beginning, now feels hot. Low side hose @ evap core never felt cold. Any ideas? Thanks, Mike
Submitted: 1 year ago.
Category: Classic Car
Expert:  kalamykid replied 1 year ago.

What where the high and low side readings?

Expert:  kalamykid replied 1 year ago.

And just to be clear, you did not pull a vacuum on the system before you recharged?

Customer: replied 1 year ago.
vac pulled for about 30 min. Lo side= 0-10 Hg/in, Hi side=150-175 psi.
Expert:  kalamykid replied 1 year ago.

Did it hold a vac for at least 30 minutes?

Customer: replied 1 year ago.
no leaks.
Expert:  kalamykid replied 1 year ago.

Then you do not have enough freon in the system. the high side reading should be around 250 and the low side should be around 40-45

Expert:  kalamykid replied 1 year ago.

I am sorry you are using r12 correct? the l;ow side should be around 35-40

Customer: replied 1 year ago.
R-12; found 8 cans at a swap meet a few years back.
Customer: replied 1 year ago.
We put in about 2 oz of ester oil (did not drain compressor) and 4 12oz cans of R-12.
Expert:  kalamykid replied 1 year ago.

So you have put 4 cans in the system?

Customer: replied 1 year ago.
4 12oz can. We had a little issue on one can and lost some, but still got probably 75% of that can and all of the others.
Expert:  kalamykid replied 1 year ago.

With a 12 oz can you only get about 10 oz out of them. if everything goes well when charging this system you will use almost 5 full cans. Add one more can to the system and see what the low and high side readings are. If it starts to freeze up, unplug the low side pressure switch till it thaws and then reconnect the switch and keep charging.

Customer: replied 1 year ago.
Put in another can of R-12, no change. To reinerate: evap tube that expansion bulb wrapped to does not get cold, which it should. Also, back of compressor got cold/frost at the beginning of charging, then went to hot. We are leaning toward the POA or expansion valve, unless you have something else in mind.
Expert:  kalamykid replied 1 year ago.

What where your pressure readings high and low?

Customer: replied 1 year ago.
low=10, high= 175
Expert:  kalamykid replied 1 year ago.

It will not be the expansion valve. If the valve was bad you would have equal pressure or very high high and very low low pressures. Did you loose pressure after letting it sit with the air off? Are you sure it does not have any leaks? Even with it holding a vacuum it can still have a leak under pressure.

Expert:  kalamykid replied 1 year ago.

The readings say it is still low on freon.

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