Prior to recharging AC, gauge reads MAX pressure?

Tiny
BSULLI4
  • MEMBER
  • 2002 HYUNDAI ELANTRA
  • 4 CYL
  • 2WD
  • AUTOMATIC
I bought an A/C recharge kit with a pressure gauge for my 2002 Hyundai Elantra. When I attach the hose to the low pressure port in the car, the gauge jumps up to a maximum pressure reading. I've never recharged my system and the car blows outside temperature air. So what could the problem be?
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Monday, May 30th, 2011 AT 11:28 PM

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Tiny
CARADIODOC
  • EXPERT
If there is enough refrigerant still in the system that some is liquid, the low and high side will equalize and the pressure will be somewhat close to outside air temperature. If it's 70 degrees, you could have over 80 pounds of pressure in the system. If you were to bleed off a little vapor, some of the remaining liquid would vaporize and expand causing the pressure to go right back up to where it was. Pressure in the system will not drop until enough refrigerant is gone that what's left is all vapor.

When you run the compressor, the low side will get drawn down to a lower pressure and the high side will go up. The compressor will typically cycle rapidly on and off. If it does not turn on, you may have to jump the low-pressure cutout switch to keep the compressor going.

If the can of refrigerant doesn't empty within a minute, place it in a pot of hot water. Be sure to wear safety glasses at a minimum. A face shield is better. Escaping refrigerant can freeze eyeballs and cause frost bite.
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Monday, May 30th, 2011 AT 11:55 PM
Tiny
SATURNTECH9
  • EXPERT
Then You need to take it too a shop to have the a/c looked at sounds like you could have a restriction in the line somewhere bad compressor inop cooling fan etc. Sounds like trying to charge it would be just dangerous and a good chance you could get hurt trying to fix it yourself.
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Tuesday, May 31st, 2011 AT 12:01 AM
Tiny
BSULLI4
  • MEMBER
So how does one "jump the compressor"?
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Tuesday, May 31st, 2011 AT 6:28 AM
Tiny
CARADIODOC
  • EXPERT
Locate the low-pressure cutoff switch. It will be on the hose going from the firewall into the compressor and will have two wires on it. Unplug the connector and connect the two wires together with a stretched out paper clip, cotter pin, or piece of wire. That will defeat the switch and let the compressor run.

If you have a high reading on the gauge already you shouldn't have to bypass the low-pressure switch. The compressor might cycle on and off rapidly at first but that will clear up once the refrigerant gets drawn in.
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Tuesday, May 31st, 2011 AT 7:50 AM
Tiny
SATURNTECH9
  • EXPERT
Lets try this with the car cold turn on the a/c and see if there is power going to the white wire to the compressor if there is and the compressor isn't running then you have a bad a/c compressor.
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Tuesday, May 31st, 2011 AT 6:38 PM
Tiny
BSULLI4
  • MEMBER
So I've gotten under the hood to take some pictures. There are two wires - both emerge from the compressor. One of them goes to a plug. That plug joins other wires and goes thru the wall of the car, presumably to the dashboard. The second wire goes to a screw which is screwed into the compressor. Here are a couple of pictures.

I went ahead and tried to charge it with some r134, but it wouldn't take any. When I first attached the pressure gauge to the low line, the reading was past the maximum the gauge could go to, 100psi. Watching the pressure gauge while I attempted to add freon, I saw it dip momentarily when I opened the freon, but it jumped back up.

Any thoughts on how to get the compressor going?
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Thursday, June 2nd, 2011 AT 6:30 PM
Tiny
CARADIODOC
  • EXPERT
If you have 100 psi in the system, it's not cutting out due to the low-pressure-cutoff switch. You have some other problem, and it's very likely the system might not be low on charge.

The next thing I'd look at is the compressor relay. It will be in the under-hood fuse box. The easiest way to describe it is to remove it, pop the cover off, reinstall it that way, then squeeze the contact. If the compressor engages, that part of the circuit is working and the problem is in what controls that relay. If the compressor does not engage, there is a problem in the wiring to the compressor. That would include the fuse that feeds the contact in that relay. The clutch coil itself could be open but that isn't real common. You could prove that by unplugging the connector, then connecting the two terminals in the compressor side of the plug with two jumper wires right to the two battery posts. If it still doesn't click to engage, the clutch coil is defective.
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Thursday, June 2nd, 2011 AT 6:58 PM
Tiny
SATURNTECH9
  • EXPERT
The one going to the screw to the case of the compressor is ground start the car up and turn the a/c on see if the other wire has power to it. If it does and the compressor isn't running you found your problem.
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Thursday, June 2nd, 2011 AT 8:12 PM
Tiny
BSULLI4
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Where can I get a diagram or something of the fuse box so I know which one to pull?
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Thursday, June 2nd, 2011 AT 8:51 PM
Tiny
CARADIODOC
  • EXPERT
There's typically a chart under the cover. Otherwise use a test light to test all the fuses. They have two tiny holes on top where you can poke the test probe. A voltmeter will work too. You're looking for any fuse that lights the test light in one test hole and not the other one. If the light turns on from both holes, the fuse is good and that circuit is powered up. If the light is off at both holes, that circuit is not currently turned on so that method won't work for testing that fuse.
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Thursday, June 2nd, 2011 AT 9:02 PM
Tiny
BSULLI4
  • MEMBER
Problem SOLVED! The fuse labeled HORN A/CON was bad. I was wondering why my horn had quit working, no idea that the two problems were connected. Thanks for all of your help guys. I'm driving to Massachusetts tomorrow from Denver -- a three day drive that would have been miserable but now will only be EPIC.

Thanks!
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Thursday, June 2nd, 2011 AT 9:19 PM
Tiny
CARADIODOC
  • EXPERT
Dandy news. Chrysler bundles multiple circuits like that too for a very good reason. You knew the AC wasn't working, but you might never know the horn wasn't working until that kid on a bicycle rode out in front of you!

Of the two, the horn is the most likely item to short. If that's what is failing, they aren't usually intermittently shorted; they typically short completely, then the fuse blows each time you turn on the horn. If you have two horns, a low note and a high note, unplug one, then see if the fuse still blows, (if and when it becomes a permanent short). That will help you decide which one needs to be replaced.
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Friday, June 3rd, 2011 AT 12:40 AM
Tiny
SATURNTECH9
  • EXPERT
Glad to hear you got it figured out thats what were here for.
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Friday, June 3rd, 2011 AT 6:03 AM

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