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Topic: a/c expansion valve

in Forum: C3 Cooling and Heating Systems

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a/c expansion valve (1/9)
9/6/18 4:27pm

Drose

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Solon, OH - USA

Vette(s):
1981

Joined: 10/14/2015
Posts: 37

So I have been trying to get my a/c working and it is a on going battle. As I try to identify the A/C parts on my 1981 vette, I can't find an expansion valve. This valve is pictured in the parts books and I do not see one on my car. If I understand its fuction correctly this valve controls the flow of R-12 or 134a and through this valve I can increase the flow or decrease the flow.

My unit blows cold air and does not have a leak that has been found. The problem is the cycling time for the compressor, it is 5 seconds on and then 5 seconds off and sometimes the air is barely cool and other times it is nice and cold. I figure a compressor can't last long in this situation?

Any ideas where the valve is or suggestions to remedy my problem will be greatly appreciated!

Thanks

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Re: a/c expansion valve (2/9)
9/6/18 5:59pm

73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 866

Have you checked the charge level? Rapid cycling can be a sign of a low charge.

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1973 L-82 4 spd

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Re: a/c expansion valve (3/9)
9/7/18 11:37am

Drose

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Solon, OH - USA

Vette(s):
1981

Joined: 10/14/2015
Posts: 37

I haqve checked the charge level more than three times. Thanks for the suggestion.

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Re: a/c expansion valve (4/9)
9/7/18 11:51am

Have you checked the pressure on the high and low sides when the compressor cuts out? It could possibly be one of those sensors is going bad.

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1973 L-82 4 spd

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Re: a/c expansion valve (5/9)
9/7/18 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: 20128

'81 Corvette should have an orifice tube, not an expansion valve.The orifice tube will be in the small(high pressure) line going into the evaporator core, right where the line connection is.

You don't say what the pressure readings were on the high and low side while running, so diagnosis is a little tough.

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Re: a/c expansion valve (6/9)
9/8/18 12:55pm

Drose

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Solon, OH - USA

Vette(s):
1981

Joined: 10/14/2015
Posts: 37

I was told the pressure numbers were what they should be when it cuts in and out. Where are the sensors located that you are talking about? Thanks for your help.

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Re: a/c expansion valve (7/9)
9/8/18 1:10pm

Drose

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Solon, OH - USA

Vette(s):
1981

Joined: 10/14/2015
Posts: 37

When using a gauge set by a certified mechanic, he told me the pressures were where they should be for cutting in and out. Sorry I don't remember the numbers. When I used a auto zone refill bottle the pressure was in the high green area when it cut in and the low green area when it cut out so I never added any charge. Thanks for enlighting me about the orfice tube, it has been removed a couple of times and always looks clean. I have had three different technicians work on this a/c unit and have to date have not been able to get it to work properly for more than 24 hours. Any suggestions are welcomed. I have had it dye tested for leaks and there does not appear to be any, I have had it evacuated and refilled three times and it still cycles on and off every 5 seconds.

Thanks for your help

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Re: a/c expansion valve (8/9)
9/8/18 2:26pm

Drose said: I was told the pressure numbers were what they should be when it cuts in and out. Where are the sensors located that you are talking about?� Thanks for your help.

On the A6 compressor one of them was located on the back of the compressor and I'm not sure where the other one is. But you have an R4 compressor and I don't know where they are. One of the three places you had it to should be able to tell you though.

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1973 L-82 4 spd

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Re: a/c expansion valve (9/9)
9/9/18 11:43am

Drose

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Solon, OH - USA

Vette(s):
1981

Joined: 10/14/2015
Posts: 37

Thanks, I will find out, appreciate the help.

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