It's Hot in Here! A/C problem

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  #1  
Old 07-29-05, 11:00 AM
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It's Hot in Here! A/C problem

Hello-

1998 Chevy Prizm, Auto. Earlier this week we were on a 2-hour road trip. An hour into it, the a/c starts blowing hot humid air. I turned it off and waited 15 minutes. Turned it back on. It ran cold for about 5 minutes, then hot and humid again. Couldn't get it to run cold for the remainder of the trip. Next day, I tried it again. It ran cold for 5 minutes, then hot and humid. Never worked since.

A friend at work suggested trying to recharge the system. I bought one of those cans with the gauge from walmart. When I hooked it up, the gauge went to RED-Danger. Yes, it was on the low pressure side. The gauge won't hook up to the other (right?).

When I hit the a/c button, the car revs more "under load" if you know what I mean. However, I can see anything turning on the front of the compressor. Mind you, I'm not a/c proficient, but the book says a clutch should rotate. The back of the new can's instructions say that it may not turn if the charge is down, but, like I said, it's shooting up to the RED-Danger zone on the gauge.

Ideas??
 
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  #2  
Old 07-29-05, 03:41 PM
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It's shooting to the red danger area because the compressor isn't running. When the compressor is running it will drop the low-side pressure.

If the compressor isn't kicking on it is very likely low on refrigerant. Put the gauge on the new can of refrigerant and start charging the system. I usually flip the can over until the compressor kicks on (so you'll be charging as a liquid).

Another thing to keep in mind is the rather large swing in pressure you will get with r-134a with ambient (outdoor) air temps. If it's really hot out (90 F+) you should charge to the top of the "full" range. If it's rather cool out (75 F and under) you should charge to the bottom of the "full" range on the gauge.
 
  #3  
Old 07-29-05, 10:06 PM
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I'm not trying to sound like I doubt you, but I want to keep all my fingers in place. Why would I hook up a can to a system that is already showing in the red zone? Wouldn't that be like asking to have the can blow up in my face?

If the gauge is already showing max psi on the gauge, how can any recharging take place? And more importantly, how can the system be low on refrigerant and still be showing so high a psi?

To clarify, I have not yet hooked up the can to the one end of the gauge. I've only hooked it to the low-side valve and got instand red zone readings. Should I now hook up the can and "charge" it?

I know I'm sounding chicken. Sorry. Thanks for putting up with me. Too many
 
  #4  
Old 07-30-05, 06:22 AM
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When you turn the A/C on, does the electric fan(s) come on? Some models require the fan to complete the compressor circuit. I think I'd take a look at the fuses and relays for both the compressor and the fans, and if you have access to a test light, see if the clutch is getting power when the A/C circuit is turned on. Very well could be the clutch has gone bad. Personally I agree.. I need all my fingers to type with
 
  #5  
Old 07-30-05, 06:45 AM
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Question

Is the A/C compressor clutch kicking on the compressor? Just watching the pulley go around on the compressor does not mean it is on it free wheels when off.
Make sure that the front of the compressor or the clutch moves in when on.You might hear a click as it pulls in.
 
  #6  
Old 07-30-05, 08:34 AM
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Yes, the fan kicks on when I turn on the A/C.

No, the clutch is not engaging. No click and no visible movement. The instructions say to start charging it when this happens, like the one fellow said. Could it be so low on refrigerant that the clutch plate cannot kick on.

No, I don't have a tester. I can see about replacing the compressor relay, but wouldn't that just go out, and not come back on again? My "symptoms" include coming back on about three times before finally giving up the ghost.

Thanks
 
  #7  
Old 07-30-05, 09:01 AM
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Agreed, it's not likely the relay acts that way..But with electrons, anything is possible.. LOL On many cars, the relay for the A/C compressor is exactly the same relay that controls the horn. (verify part numbers!) If they are the same, swap them. if the a/c starts working and the horn no longer works, it's the relay..If they aren't the same, it's time to check voltage at the compressor..You can pick up a cheap test light at Radio Shack, and check to see if voltage is being applied to the clutch..
 
  #8  
Old 07-30-05, 09:10 AM
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Will check into the relay swap. Great advice.

How do I use the tester once I get it?

Are you saying that I shouldn't add the refrigerant at this time?

Thanks again.
 
  #9  
Old 07-30-05, 09:21 AM
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Swapped the relays. The both make the horn work. bummer.

How do I test the circuit on the compressor? By the way, the clutch will free spin by hand. I don't know if that's useful, but I wanted to include it.

Thanks
 
  #10  
Old 07-30-05, 09:27 AM
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Lightbulb

I don't mind being doubted I do it all the time.

You misunderstand when that gauge's reading is to be taken literally. If you hooked it up to a can of refrigerant with 1/100 of the refrigerant left in liquid form in the can, that gauge would go to the red danger zone on your gauge.

The gauges that are only labeled "low, full, danger" are only correct when the compressor is running.

The pressure on the low side is always higher when the system is off (or the compressor isn't running). It will drop when the compressor kicks in.
 
  #11  
Old 07-30-05, 10:01 AM
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I'm sitting here at home (in the cool A/C LOL) with no information data available to me, so am going on memory..The car has a fairly small refrigerant capacity, he stated it worked for a short time then quit, worked again, then quit totally..He has pressure on the guage, So, my line of thought is not a charge problem, but a bad clutch.. It wouldn't be the first time today I was wrong, but the symtons he's described, have me leading there first..As small as the system is, it seems like a gauge reading high should allow the clutch to cycle. The electrical checks I'm suggesting are quick and painless, and as he's stated he's not experienced in A/C work, these checks will keep him safer, and hopefully keep him from over charging the system..I do agree, an A/C system in "static" mode (not on) will show the low side being a lot higher than it should be, compared to what it'll read when the compressor is running, but that indicates a presence of freon/pressure..I have no info available to me that shows at what pressure the clutch will be cut off for low pressure, and as he doesn't have a gauge that reads in PSI it'd be of no use to have those numbers..A test light to confirm voltage at the clutch will definately prove me wrong..
 
  #12  
Old 07-30-05, 01:46 PM
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Another idea

Another idea I have is just hot wire the clutch with engine running you will see two wires on connector or maybe one if it is grouned thru the compressor.
You could apply 12 v battery voltage to the wire and see if clutch engages.(use kind of a thick guage wire like).If I recall there is a low pressure switch that prevents compressor from going on.Doing this jumper will bypass that switch. Also a test light like stated would be of great value to see were you have voltage.
 
  #13  
Old 07-30-05, 05:43 PM
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Take a hammer and lightly tap the clutch center section in slightly (very carefully without getting yourself in a dangerous position as the vehicle has to be running and AC switch set to on and calling for cooling) to see if it will engage. I have seen some that just need a simple air gap adjustment but first verify 12 volts at the wires to the clutch coil. If no voltage there check your low pressure switch if this vehicle is a Fixed Orfice tube system with a accumulator can they are typically mounted on the side of the can. Pull the wire if it is a two wire plug simply short across it with a piece of wire and your compressor should engage. BIG CAUTION if your car uses a TXV type valve it will have a trinary switch with three wires NEVER SHORT ACROSS A THREE WIRE SWITCH as one leg feeds five volts to your computer and you will fry your computer and buddy those things are not cheap!!!!!!!!!!!!!!!!!!!! post back if you need more help. A good set of manifold guages makes AC work much easier I have seen sets for well under 100 bones! I have sold some of my old working sets at yard sells for around ten bucks.
 
  #14  
Old 07-31-05, 06:03 PM
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Originally Posted by msargent
He has pressure on the guage, So, my line of thought is not a charge problem, but a bad clutch.. It wouldn't be the first time today I was wrong, but the symtons he's described, have me leading there first..As small as the system is, it seems like a gauge reading high should allow the clutch to cycle.

I absolutely agree. I am glad there people here who have had their coffee.



The OP saw how full of it I probably was.... good thing!

Hopefully you're able to get it going again.
 
  #15  
Old 08-02-05, 05:34 PM
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Wanted to stop by and let you guys know that I took it to a garage. Sorry, I'm not too handy and some of the stuff you said to do was beyond me.

Anyway, turns out that there was a broken wire going to the compressor which caused it not to work. They put on a new wiring harness, charged with new freon (which I didn't need), and charged me with $120. Oh, well. Lot better than a new compressor. I'm thankful.
 
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