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#1 |
A-Adam A-Adam
Join Date: Apr 2003
Location: Sarpy Co. Ne. South of Omaha
Posts: 263
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Air conditioner problem
I finally replaced the clutch on my AC. It is cooling well. Works fine at idle and around town but when i get out on the highway between 55-65 it freezes up.
Any Ideas? ![]() ![]()
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70 3/4 ton GMC Camper Special Last edited by s95930; 07-02-2005 at 10:46 PM. |
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#2 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Does the ac continue to work when the ice forms on the outside of the pipes?
Jim |
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#3 |
Registered User
Join Date: May 2005
Location: South Mississippi
Posts: 81
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Do you have condensor coil cooling fans. Do you have a seperate relay to turn on your fans or is it common with your compressor clutch relay. I had the same problem with an old air system. The fan motors are permenant magnet motors, at highway speeds the blades are driven by the wind and the motor becomes a generator. It produced enough power to hold the clutch in and freeze everything up. I added another relay to isolate the fans from the clutch and have had no problems since. Don't ask how long it took to figure this one out. Steve
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1969 C10 Long Step,355,700r4w/lockup, HEI,Weiand,750 Performer,1.6 rockers,Camel Humps,Comp 262Extreme,Hedman,2 1/2"pipes, tele/tilt,SunRoof,ps,Disc pb,ac,Cragar,eaton,Corvette style roll pan, Bowtie louvered tail gate,lowered 2/2. |
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#4 | |
A-Adam A-Adam
Join Date: Apr 2003
Location: Sarpy Co. Ne. South of Omaha
Posts: 263
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Quote:
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70 3/4 ton GMC Camper Special |
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#5 | |
A-Adam A-Adam
Join Date: Apr 2003
Location: Sarpy Co. Ne. South of Omaha
Posts: 263
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Quote:
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70 3/4 ton GMC Camper Special |
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#6 |
Active Member
![]() Join Date: Jun 2002
Location: L.A. Lower Alabama
Posts: 453
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Could be a low on refrigerent this will cause the evaporator to freeze up. Might try adding a small amount at a time to see if it helps.
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1969 C10 350 3spd 1995 GMC 3500 XC 350 dually When Thomas Edison worked late into the night on the electric light, he had to do it by gas lamp or candle. I'm sure it made the work seem that much more urgent. George Carlin |
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#7 |
blood type; Retumbo
Join Date: Jan 2004
Location: next to my reloading bench
Posts: 10,269
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I could be wrong but it sounds like a POA valve problem.
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Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card |
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#8 |
Lovin' Life in Miss.!
Join Date: Mar 2004
Location: Puckett, Mississippi
Posts: 1,937
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Clutch on our trucks is engaged continuosly when a/c is selected. Evaporator freeze-up in a properly functioning system is prevented by the poa (pilot operated absolute) valve.
I am too new to A/C to arm chair diagnose your problem. You can try asking over in the a/csource forum. Be prepared to provide high/low gauge readings though.
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The truck... you hear that? No really, you did hear that?!!! |
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#9 |
More Cowbell....
Join Date: Mar 2004
Location: Puckett, MS
Posts: 3,569
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I agree with zeke. Check for low refrigerent. That has happened to me before.
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There once was a member from Puckett.....Who ( fill in the blank blank blank ) bucket |
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#10 |
Senior Member
![]() Join Date: Dec 1999
Location: Southern California
Posts: 2,810
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Freezing can be caused by an overcharge condition, not an undercharge. Low airflow at the evaporator or condenser can also cause freezing. Seeing as you probably have plenty of airflow across the condenser at highway speeds- that is out. Leaves and other crud coming in through the cowl can clog the evap coil. A sticking POA valve is another definite possibility. Check the airflow in the cab at all fan speeds. if it is fine probably the POA.
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Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746 |
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#11 |
Registered User
![]() Join Date: Jul 2000
Location: Hampton, Ga, USA
Posts: 217
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I had same problem, replaced expansion valve and it did not cure problem. Tried to find new POA valve but they are not avail. Repaced POA valve with an adjustable valve that cycles the compressor off before evap. freeze up. Works fine now.
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68 Short Stepside, 350, quadrajet, 700r4, 3:73 posi, power front discs, HEI, Factory Air, Tilt, Tach, accelerator cable instead of rod, sway bar. 96 Impala SS 97 Monte Carlo |
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#12 |
Registered User
Join Date: Feb 2000
Location: Edmonds, WA
Posts: 322
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Just to be clear (I am an AC novice), the compressor does not cycle on and off if the truck has a factory set-up? If that is so, isn't that unusual compared to the way most vehicles' AC behaves?
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'72 Chevy Suburban Custom Deluxe 10, 402/TH400 |
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#13 |
Registered User
Join Date: Aug 2002
Location: Muskogee, Oklahoma
Posts: 2,914
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You ar correct, as I am an A/C novice myself, I asked this same question when I was getting ready to recharge my system after re-installing a new compressor. My system was bone dry and I turned on the A/C and the compressor stayed engaged. This as I was told is normal function for these model year trucks. There is a single switch that supplies power to the compressor clutch and when this switch is made the compressor stays on always.
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#14 |
Lovin' Life in Miss.!
Join Date: Mar 2004
Location: Puckett, Mississippi
Posts: 1,937
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You can get a poa eleminator kit that will turn your system to a cycling clutch. Old air products. Around $100.
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The truck... you hear that? No really, you did hear that?!!! |
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