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Unusual A/C issue

 
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  #1 (permalink)  
Old 30 Apr 2011, 10:17 am
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Default Unusual A/C issue

Ok I have a 2001 PT. A few months ago I had someone change the radiator. I don't know if that has anything to do with my problem or not. Anyway, As things started to warm up I tried to use the A/C and it didn't work. I hooked the A/C gauge to the car and it is reading 60 to 70 psi which is into the red on this gauge. I started the car and the compressor isn't kicking on. I pulled the low pressure switch off and shorted it with a piece of copper. The car immediately started surging at idle. I disconnected the jump wire and hooked the switch back up and it is still surging. I'm at a loss. Any ideas?
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Old 30 Apr 2011, 10:28 am
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Default Re: Unusual A/C issue

First of all, if the pressure was low (as you read it) why didn't you charge it up and why did you try and test the low pressure (recycling) switch. When the pressure is low, the HIGH pressure switch on the compressor is the one that will stop the compressor from coming on. get the system fully charged up to the normal specs and go from there. Second, if you are low on R134a, you have a leak somewhere. You'll have to find it or you'll just loose the new charge.

Just taking a guess on this part but because the compressor is trying to come on (Your A/C is ON) and the high pressure switch is shutting it down because of the low pressure (R134a) in the system, that may be the surging you experiencing.
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Last edited by CREWZIN; 30 Apr 2011 at 10:30 am.
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Old 30 Apr 2011, 10:46 am
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Default Re: Unusual A/C issue

Well I if I'm reading the gauge right then the low pressure isn't low it is way to high. If I lost any 134 I am guessing it was when they changed the radiator? They done it way to quick to have drained the A/C system. So what do you think my next move is? try and shoot some 134 in?
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Old 30 Apr 2011, 11:00 am
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Default Re: Unusual A/C issue

I'm not sure of the exact pressures you should have, but find out and get it straightened out. Then if the compressor doesn't come on, it could be a defective high pressure switch (on the compressor itself). The low pressure (or recycling) switch only cuts the system on and off for proper operation. When that goes out the system freezes up but first the compressor needs to be ON. If all the fuses are good and the pressures are correct, the main culprit is the high pressure switch.
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Old 30 Apr 2011, 04:27 pm
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Default A/C issue - Couple Thoughts & Fan Relay Questions

Just joined this morning, my first post ...

2007 PT Cruiser
46,000 miles
Fairly Basic Model
Wife is Primary Driver (until something breaks)


Having problems with my AC also. Trying to diagnose. My air actually blows cold for long periods of time and then will blow warm.

First place I wanted to check is the fan. I've read:

(i) That the fan should always turn on when the AC button is pushed. I push the button, hear the AC Clutch Engage (it puts a load on the engine and you can hear it sort of pulse as the engine adjusts to the higher working load). BUT - no fan. I had the hood open in the driveway, got out and look carefully and the fan definitely does not run. (I'm in Florida and its 81 F today).

(ii) Possibly related, my wife reports that the car has had issues of really idling rough at stop lights when the AC is on. If I understand other posts correctly, the radiator fan should run constantly when the AC is turned on and if it isn't working, the extra work load from the AC will really make it idle roughly until the high pressure switch trips off the compressor. All of this information reasonably describes my situation.

So here's my unique problem:

I've located the fan relays - they are located on the passenger side of the fan shroud. I understand how to test the relays and how to jumper out the relays to test the fan motor. HOWEVER (!) I cannot get the darn things out! They are marked "Tyco" on the top so I think that I'm looking at the right component. There is a plastic clip on the shroud side and when I release the clip the relay will lift straight up and off its mount. The problem is I cannot release the relay from the wiring bundle that comes up from underneath.

There is a second plastic clip located on the firewall side of the relay. Remember the clip to release the whole unit (wires still attached) is on the shroud side. The clip on the opposite side of the relay (fire wall side) looks like it should pop open and the wiring harness should pull out of the bottom of the relay. If I could do this the rely would come out and the wire (and presumably male plug) would stay in the vehicle.

Everything is very tight - but I've been able to open the second clip (again the one that connects the relay to the wiring harness that comes up from the bottom. However, it doesn't want to pull apart.

Has anyone ever had this experience and am I missing something?


Finally, back on the pressure questions related to this post:

My Xterra AC requires 35-50 PSI on the low side and 225-275 on the high side. If you're reading your pressures on the low side, you're high. 60 - 70 won't kill it, but it is hard on the compressor. My Xterra is "high on the low side" because that's what it takes to get the high side up to the minimum of 225 PSI. However, my compressor (or the electric clutch) is dying on that vehicle so an overcharge is sort of palliative care.

The Harbor Freight HVAC Gauges are a pretty good investment if you're going to be "messing about with cars". They are typically on sale for $44 and you should be able to scare up a 20% off coupon. The pressures for my Xterra are fairly common for auto AC so you wouldn't be too far off if you used them.

That's all I've got on the pressures, but think that you might have similar problems on the fan side.

Finally, do we know for sure sure sure that the fan should come on when the AC is switch on? My guess if that is true is that my slow fan relay is shot and that my vehicle doesn't overheat because the high speed relay kicks on the fan when it gets hot. (Just a guess).
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Old 30 Apr 2011, 05:35 pm
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Default Re: Unusual A/C issue

Ok so I'm some what an idiot lol. When I pulled the low pressure switch off to short it I knocked a vacuum line off and thats why it was surging. So I am back to square one. My compressor isn't kicking on. I crawled under and looked the best I could and there is a ground wire that is hanging disconnected. Would the compressor have a ground wire going to it? I checked fuses and relays and they are all good.
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Old 23 Jul 2011, 03:25 pm
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Default Re: Unusual A/C issue

can you change the High pressure switch on the compressor it self ??how hard is it to do

changed low pressure switch did not fix issues just keeps cycling on an pressure goes way up then blows off

not sure if its the rad fan as we got it to work other day but tried again next day same thing again does the high pressure switch control the rad fan for A/C to shut off
also when compressor comes on at idle in car shakes like it wants to stall could it be the : Idle Air Control (IAC) Valve
causing this
any info would be great please
need to get this fixed hot as hell in ontario right now
thanks
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Old 25 Jul 2011, 12:14 pm
themadgreek187's Avatar
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Join Date: Aug 2008
Location: Jax FL
Posts: 104
Default Re: Unusual A/C issue

Quote:
Originally Posted by ginuwine View Post
can you change the High pressure switch on the compressor it self ??how hard is it to do

changed low pressure switch did not fix issues just keeps cycling on an pressure goes way up then blows off

not sure if its the rad fan as we got it to work other day but tried again next day same thing again does the high pressure switch control the rad fan for A/C to shut off
also when compressor comes on at idle in car shakes like it wants to stall could it be the : Idle Air Control (IAC) Valve
causing this
any info would be great please
need to get this fixed hot as hell in ontario right now
thanks
u have to have the a\c flushed to remove the high pressure switch. i have done the LPS and HPS to no avail. i think my PCM is bad. too bad the dealership wants $90 to diagnose it. a/c is fine in the AM after the car sits overnight.
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