AC freezing up

[William F.]

My factory R12 ac '67 was cooling fine till about a mo ago when wouldn't pull down below 50 Degrees. Sa a few bubbles in site glass so empirically added one can of R12. Now freezes up. I should mention ac has the POA replacement device but installed that several yrs ago and all was well till what I now describe. Overcharged or something stopped up or switch on POA replacement which turned compressor on and off bad? I plan to get my technician to put gages on and get reading, but till then, do any of you have suggestions?
Thanks

[Stephen L.]

Re: AC freezing up

Probably low on Freon. Check the pressures with a gage set.

[Bill M.]

Re: AC freezing up

Second that is

[Harry S.]

Re: AC freezing up

Is this an expansion valve problem? If it doesn't close you will get ice. Check the line from the expansion valve to the bulb. Has the bulb become exposed?

[William F.]

Re: AC freezing up

bulb seems to still be against the return "pipe" and with insulation around it.

[Domenic T.]

Re: AC freezing up

William,
If you have the A6 then don't use the cycling. They were not built for that. If the evap froze then turn the A/c off. The cycle burns the clutch and also causes the hub to go off center and cause the front seal to loose it's center and leak. I have always preached that IF you want your original comp to last then turn it on @ idle, or start the engine with it on! clutch is metal to metal and will have to self center wen engaged. If not then seal failures, especially with the China double lip seal. One thing China got right was the Hub clutch. They are right on, but do not have cosmetics of earlier hub clutch.
When I spin the original hub clutches they are all over the place. Balance, wobble, and specs. If it freezes you seem to have a +. Complaints are that they don't.

Dom

[William F.]

Re: AC freezing up

Domenic,
I understand your concern about stress on compressor clutches with the cycling that occurs if one had replaced the POA valve with the so called upgrade which works by cycling the compressor on and off . However, if you want to replace a bad POA valve with a good one rather than going to the "upgrade " device that cycles, where do you get a reliable POA valve? Some say the rebuilt ones are a waste of money and how would you know an old new old stock one would be reliable? Sources?

[Mark E.]

Re: AC freezing up

They can be pricey, but find an NOS POA and test it. There are a few guys on eBay who sell them. Old Air Products has a selection of NOS parts too; I scored a couple of nice expansion valves from them awhile ago.

[Domenic T.]

Re: AC freezing up

William,
I was under the impression that with a new POA you had the option not to hook up the cycling.

Dom

[William F.]

Re: AC freezing up

How to test a POA??

[William F.]

Re: AC freezing up

Some how we're not on same page.With a POA installed as '67 Corvettes came from factory with, compressor doesn't turn on and off-"cycle". It stays on with you turn AC on. It's with the socalled "POA upgrade" which replaces the POA that turns compressor on and off depending on adjustment you can make.