ac blows cold then hot

Jim Fairbanks

wrench
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Nov 17, 2006
Messages
4,508
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38
Location
Portland,Oregon
Make
chevy
Model
conversion van
Year
1996
Miles
190000
Engine
5.7
hey guys...This is on my van. I don't do ac, so I am not sure what is wrong.It is a 1996 Chevy conversion van, 5.7..It will be working fine and then it starts blowing warm air.Sometimes after awhile it will start getting cool again but sometimes it won't till the next day. I had the ac fixed about a year ago, the guy put a new compressor in it and had it working good for awhile. I need to take it in but wanted to get an idea of what might be wrong with it....thanks....Jim
 

billr

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The first thing to suspect is a low refrigerant charge. Does the compressor rotate when A/C is supposed to be on, but you get only warm air? Is the front of the condenser reasonably clean? Is the engine cooling fan working? If it passes those quick visual checks, then the next step is to connect high/low gauges.
 

NickD

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Aug 28, 2007
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GM has been known to use an interference fit on the clutch assembly and the clutch gap when the AC is off should be less than 0.020". Cold AC coil current is about 4 amperes, but when that coil gets hot, that current drops to around 3.6 amperes. Excessive clutch gap, reduced current when hot, the clutch won't engage.
So easy to check, just look at it. Is a tool for removing and installing that clutch, matter of fact, three of them, keep on changing the design so you have to buy more tools.

You sure don't want a clean compressor shaft, want a rusty one, less chance of that gap increasing. Most others used shims and a nut, they don't have this problem.

In 1994 Crooked Al Gore forced the EPA to instantly ban R-12 and switch to R-134A, with R-12, GM was using a double lip seal, when R-134a came out they switched to a single lip seal. Many paid a fortune for a new compressor, when all was needed was to replace that compressor single lip seal with a double lip one. Talk about screwing everyone. People with R-12 could not buy this refrigerant anymore, but some could, instead of 30 cents a pound was 80 bucks a pound.

To switch to R-134a on most vehicles, had to be done firewall forward, but no components were available. At the same time, Crooked Bill Clinton told the IRS for the huge rebuilding industry we had before him to evaluate cores at finished retail value, put them all out of business, so he could open the doors to China. This guy should be hung, and this is not political, but fact in the automotive industry. Have seen millions of grown men cry and couldn't do a darn thing about it.

The Automotive Parts Rebuilders Association filed a complaint with the supreme, but they never looked looked at it until 8 years later, also in the crook class. This really opened the door for China that made Clinton, Gore, and Bidden, billionairs at the expense of our jobs. and parts replacement cost.

Again, not political, but cold hard facts. Political is lying.
 

jigfeett

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We had one on a trailblazer that would stop blowing cold at times and it turned out to be the compressor, even though it was clutching correctly and the gap was in spec.
That one took a long time to get a final fix. The Chev dealer misdiagnosed it as a bad condenser and accumulator but the real problem was the comp. Also replaced the orifice tube which was surprisingly clean.
Long story short, new condenser, accumulator, orifice tube, compressor and the system is still working at 40° even on a 90° day. On a side note, the fan and water pump were replaced a few months earlier.
Sounds like a lot of swapnostics but with over 200k on the odo you would expect problems.
All this is big money if a shop or dealer does the work....My 2 $.02
 

brcidd

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next time it is not cooling when it is supposed to be....stop open hood, look at front of compressor- is front hub turning?...
If not- bump front of compressor with a wooden hammer handle etc..if it engages then you've just diagnosed your wide air gap.
we'll go from there.
 

nickb2

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Location
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other day, another civic with a non engaging clutch, take a shim out, work likes a charm. If no hims left, some other smart guy was there before u!;):bat:
 

NickD

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I hate connecting gauges to those quick couplers used on R-134a systems, that diaphragm seal is of large diameter has a grove in it from pressure, and may not seat properly so you have service port leaks. Incredibly stupid design...

Service valve caps are next to worthless, and if a service port leaks, no longer a 50 cent Scharder Valve, but the entire low or high side pressure line has to be replaces for as much as a thousand bucks on some vehicles plus labor.

An incredibly stupid design by both the SAE and EPA. One tiny stone chip can wreck an R-134a condenser making a stone chip on your windshield mild compared to your condenser leaking. Completely unrepairable and with that stupid women's facial cream PAG, a PITA ass to replace, system has to be flushed, purged with nitrogen, deep vacuum and have the PAG injected and what for? R-12 never hurt the atmosphere, as a matter of fact 96% of it was blown into the atmosphere by cleaning and spray cans, only 4% including R-12 and R-22 was actually used for its intended purpose, refrigeration.

Spay can propellant replaced with propane, a nice little blow touch to play with, CFC were far safer.

Can you believe this is happening in the land of the free? Sure ain't the land of the free during tax time.
 

jigfeett

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Thanks,
Swapnostics came about when you have lots of parts money and less diagnostic skills.

Never cared for the 134a service ports, I still remember back seating valves, you could shut off the system and replace the comp without recovering the system. Not such a good idea but some people did it.

I will try the clutch trick next time....
 

billr

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I sure don't know about all R134a ports of that era, but my '94 Saturn has regular-type Schrader valves, and they gleefully develop leaks. I made metal caps with O-ring to seal the ports. So far, so good...
 

NickD

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My 1982 Pace Arrow had a York compressor with those valves, also a sight glass to see the oil level in the compress, oil was not pumped with the refrigerant like in practically all automotive systems. Was possible when compressors were moved from the top of the engine to bottom, oil will leak out the seal as its heavier and has the pressure of the refrigerant to push it out. And since the system shut down is dependent on low refrigerant to shut it down, compressor would run with lubrication and it would seize up.

GM's R-12 seal was bullet proof, speculated that when DuPont received a patent on R-134a, he and Clinton got a bundle of cash to kill R-12, patents were expired on R-12 and R-22 a long time ago, and DuPont did make a small fortune, was no senate investigation on this. With R-134a, GM comes out with a single lip seal.

On some vehicles with space between the grill and condenser, was able to hang a fiberglass screen angled down, this would prevent bugs from plugging up the condenser and stones from hitting it, can't do this in these new cars.

R-12 used mineral oil, impervious to moisture, just draw a deep vacuum, and charge it. PAG oil changes to acid with moisture, PITA, system should be flushed, purged with nitrogent, draw a deep vacuum, charge the system with R-134a for pressure, inject PAG oil to do it right. Not handy with basic AC tools, should purchase a charging station.

Still advertising that R-410A does not contain chlorine that kills the ozone layer over the south pole when it going through 6 months of no sunlight that is really necessary to create ozone, crooked Al Gore blamed even R-22 that only had 1/100th the value of chlorine in it.

If they want to blame chlorine for killing the ozone layer what about millions of acres of sewage disposal plants loaded with chlorine in out drinking water?

The other bad joke, is that only 4% of the total refrigeration, auto, your ice box, refrigerated box cars, trucks, plants were using this CFC's, R-12 and R-22, for all buildings, huge stores, etc. The other 96% was used for cleaning, spray cans, and studying ocean currents.

Leaded gas that was proven to cause brain damage, took 20 years to phase out, R-12 based on a stupid theory, banned over night. Millions of vehicles were not R-134a compatible, never held the manufacturers responsible nor the uses. Single mom with three kids were held responsible.

Think it was in 1974, the newly formed EPA banned asbestos that has a 3.000 history and my company was forced to have a recall on all products, we were just using a piece of it of insulation in and enclosed cabinet, many companies used more like women's hair dryers like a sped would fly off and cause lung cancer. I was also exposed to asbestos, am 81 years old with perfectly fine lungs. Really a major problem with asbestos dust is clutch linings and brakes, but the EPA gave them years to come up with something else. And if the World Trade Centers used asbestos would still be standing.

But R-12 with zero pollution history was banned overnight and by a crook that should be locked up in prison and would be if Americans weren't so stupid. Ha, I didn't say that, was told this by Japanese Engineers, but no argument about Americans being stupid.
 

Jim Fairbanks

wrench
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Messages
4,508
Points
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Location
Portland,Oregon
So I guess it was a pressure switch that goes in the accumulator that was sticking..That's what he said....anyway it is fixed and working again...Thanks guys....Jim
 
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