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Topic: 1981 Factory Air Woes

in Forum: C3 Cooling and Heating Systems

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1981 Factory Air Woes (1/6)
7/29/15 7:33pm

apd 628
Former Member
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Joined: 6/25/2015
Posts: 4

I bought the car this past Winter, or at least what passes for Winter here in Texas. When I got the car, a lot of things did not work, and the last major issue is the AC. Since the temps are in the 100 degree range, I thought it would be a good idea to have a go at the factory AC.

I put my gauges on the system, then set the vacuum pump to work. I let it run for 45 minutes to be sure I evacuated the system, I let it sit for 20 minutes to see if the vacuum would hold, and it did. I then started adding r134a to the system, it had been updated by a prior owner a few generations back.

As the system pressures started to approache the numbers on the high and low side which would cause the clutch to start cycling, it did not. I thought my low pressure sensor cut off switch was not working right so I ran 12 volts to the driver side of the two prong plug on the compressor, and the clutch started working fine, and I filled the system to spec. as per the Chevy shop manual.

The car cooled down quite nicely, as it was blowing 46 degrees out of the vents, not too shabby since my shop temp was 95. The car has a nice auxiliary fan, and I had a couple of extra fans blowing into the intake of the radiator.

The next day I went to the parts store, and got a new low pressure cut off switch. I installed it, and fired up the system. The compressor immediately started clicking on and off quite rapidly, and I was back to blowing hot air again.

From the car, not me.

System is still pressurized to shop manual spec.

Any ideas?

Thanks

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Re: 1981 Factory Air Woes (2/6)
7/29/15 8:20pm

Sarge81

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WEST SENECA, NY - USA

Vette(s):
1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.

Joined: 12/3/2001
Posts: 2379

If all your pressures are good and the compressor is cycling, I would take the fan speed blower motor resistor off the top of the heater box and take a peak in there to see if the blend door is closed tight. If it's not closed tight or the seal around the blend door is deteriorated it will draw hot air in from the heater core.

Another thing we do with these cars is put manual shut off valves on the heater hoses to isolate the hot coolant from the heater core.

I'm also troubleshooting my A/C system since it just went out on my '81 last weekend. These cars can be a pain to get the A/C system working even somewhat cool.

______________

GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.

3.54 Dana 44

'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975

Click here to see more pics of my Vette on CarDomain.

Lifetime Member #26

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Re: 1981 Factory Air Woes (3/6)
7/31/15 1:18am

F4Gary

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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.

Joined: 8/26/2006
Posts: 1409

I don't think his problem has anything to do with the heater core or blend door.

I know nothing about a/c.

|UPDATED|7/30/2015 10:18:59 PM (AZT)|/UPDATED|

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Re: 1981 Factory Air Woes (4/6)
7/30/15 12:27pm

Adams' Apple

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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20129

apd 628 said: The next day I went to the parts store, and got a new low pressure cut off switch. I installed it, and fired up the system. The compressor immediately started clicking on and off quite rapidly,

I'd have to say the new switch you got is defective, or the connection is not quite tight enough. Check the wiring and the connector for the switch to make sure nothing is loose. Have you tried to jump 12v to the compressor again to see if the system will still cool like that? If it cools with the compressor hot wired, the problem has to be the "new" switch, or the wiring for it. Thumbs Up

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Joel Adams
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Re: 1981 Factory Air Woes (5/6)
7/30/15 1:54pm

Sarge81

Lifetime Member
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WEST SENECA, NY - USA

Vette(s):
1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.

Joined: 12/3/2001
Posts: 2379

Is this C3VR or Corvette Forum? Confused

I guess I'll head over there (CF) to offer suggestions to problems and in return get a kick in the nuts. Jeez...Sorry I said anything. I guess my similar issue and fix to my A/C was a figment of my imagination.

Sorry Joel, I missed the part of rapidly clicking on and off in "apd628's" statement. My bad. Wink

If you'll excuse me, I have to go now, my part came in. I have to go down to the shop and fix a A/C system on a '02 Crown Vic I diagnosed.

|UPDATED|7/30/2015 10:54:59 AM (AZT)|/UPDATED|

______________

GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.

3.54 Dana 44

'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975

Click here to see more pics of my Vette on CarDomain.

Lifetime Member #26

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Re: 1981 Factory Air Woes (6/6)
7/30/15 2:58pm

tb2k82ce

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Lemon Grove, CA - USA

Vette(s):
1982 C3 Collectors Edition 44000 miles, sat in the sun most of its life, My wife purchased it for me for Father's Day in 2007 from her girlfriend that had it for 19 years. It is on the road again. I'm retired but it is now my daily driver.

Joined: 10/17/2007
Posts: 2041

Darryl (Sarge81)

I had a similar issue with that door the hing was broken. Of course the hing is just plastic part of the door. I used and old binder cover that had the same type of hing. What a job to make one and fit it. I would have purchased one but how do you ever finds something like that that is in any kind of shape.

By the way I have the valves on my car. I have them on both sides of the heater core. I think I even have the valve part numbers they are two different sizes if anyone is interested PM me.

|UPDATED|7/30/2015 11:58:33 AM (AZT)|/UPDATED|

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