The A/C in my 70 seems to have a mind of its own.

It didn't work when I bought the car. After the first repair attempt it worked for five minutes, then froze up. After the second repair attempt, it froze up after just 3 minutes. Can’t figure out what’s wrong.

FIRST REPAIR ATTEMPT
For the first attempt at the repair, the unit was flushed out and checked for leaks. Because the dryer and expansion valve were old they were replaced. Also the compressor was suspect, so it was also replaced with a brand new unit. The “new” system checked out okay, and was charged up with new freon. No bubbles appeared in the dryer window and nice 50-degree air pumped from the vents. But after 5 minutes, the POA valve froze up.

SECOND REPAIR ATTEMPT
After hunting all over locally for a new POA valve, one was found and installed. The system was charged up again with new freon. And once again, it pumped out nice ice cold air...for about 3 minutes. Then it froze up AGAIN!

The only parts that haven't been replaced (hoses, condenser, and evaporator) would not cause freezing, so these parts have been ruled out as the problem. (Also because the system has no leaks and holds pressure, these parts must be okay.) Likewise, the thermo control under the dash has been ruled out because the system freezes up before the thermo control activates. (In other words, if the thermo control is bad, I won't be able to tell until everything else is running the way it should.) There are also a lot of bubbles now in the view glass on the dryer. But the system is fully charged with the correct amount of freon. Hmm. . .

This A/C unit is making me hot under the collar! (not to mention putting a dent in my wallet). Perhaps either the new expansion valve or the new POA valve is bad? But that doesn’t happen to often, almost never.

Any suggestions as to why the system is freezing up after just a couple of minutes?

Robert

Check out my former ride, a two-owner 1968 Chevelle Concours: 1968 Chevelle Concours (http://www.cornellgroup.com/Stoltz_File/Chevelles/68Chevelle.html)

See my current ride, a 1970 "SS" Chevelle Wagon: 1970 SS Wagon (http://cornellgroup.com/Stoltz_File/Chevelles/ChevelleWagon.html)


[This message has been edited by rstoltz (edited 10-14-2000).]

Check for a restriction in the suction line.

[This message has been edited by Unclepennybags (edited 06-07-2000).]

[This message has been edited by Unclepennybags (edited 06-07-2000).]

Depends on what "froze up" means. If you have actual frost or ice in the expansion valve, you have some moisture in the system. The new acc/dryer with a good 20 min evacuation should have taken care of this. Might have to pull out freon, change dryer again, evac, and recharge. Only thing I know to cause this is moisture. Sounds to me like the evac. wasn't done just right and air was left in the system.Could be something else maybe.

Make sure the sensor (bulb) for the expansion valve is in good contact and insulated.

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Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)

Heres a simple check for restrictions feel both sides of all components colder temp on the downsteam side indicates restriction. make sure the compressor side of the expansion valve is hot and the evap side is ice cold if not exp valve not getting signal from the temp bulb if temp is blowing cold then starts blowing hot make sure the fan is drawing enough air thru the condenser.Check also by trickling water over the cond. see if it startsblowing cold again. Bubbles in the site glass is not a very good indicator of freon charge measuring high and low side pressures is the only way to get it right. How many lbs of freon were put in on the last charge?

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PhilMullaly Member562 72camino TPI proj

Well, I finally got my A/C problem solved, and just in time for the 107 degee heat this week in Sacramento!

I'm no A/C whiz kid so I enlisted the help of two A/C guys I know. (Shoulda went to the second guy first, though.) The first guy did all the work in "first attempt and "second attempt" mentioned in my post above. The A/C still didn't work, however.

The second guy determined the dryer as the culprit, despite being new. He disassembled the system and discovered that the dryer was full of oil. Appraently, the first guy added 10 oz. oil to the system after installing the new compressor. Problem was that the new compressor came with 10 oz. of oil in it already. So I had 10 oz. of extra oil in the system. In addition, there was even more oil that didn't get flushed out completely in the first and second repair attempts. In all, the system had about 24 oz of oil in it!

The second guy flushed the system with freon (the higher pressure works better than A/C flush, according to him), installed a new dryer and new o-rings throughout. He charged the system and now I have nice cool, 40 degree air in town and 32 degree air on the freeway.

Much to his credit, the first guy reimbursed for both freon charges. He never got the system working correctly and felt bad for improperly twice misdiagnosing the problem.

Here an approximate breakdown of the repair bill:
POA Valve: $50
Expansion Valve: $25
Compressor: $325
Dryer: $35
Freon: $80 (After discovering that we know many of the same people, the second guy only charged me his cost for freon: $16/lb. Lucky me!)
O-rings: $5
Labor: $155

Total: $675

My sister just got her A/C repaired in her Ford Expedition: $1,400 OUCH! I don't feel so bad.

Thansk to all for the repair suggestions.

Robert

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Check out my former ride, a two-owner 1968 Chevelle Concours: 1968 Chevelle Concours (http://www.cornellgroup.com/Stoltz_File/Chevelles/68Chevelle.html)

See my current ride, a 1970 "SS" Chevelle Wagon: 1970 SS Wagon (http://cornellgroup.com/Stoltz_File/Chevelles/ChevelleWagon.html)


[This message has been edited by rstoltz (edited 10-14-2000).]