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Intermittent A/C Problem - cold at idle, warm during driving

  • Thread starter Thread starter thisxstyle
  • Start date Start date Jun 15, 2021
T

thisxstyle

New Member
Jun 15, 2021
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San Antonio
Jun 15, 2021
#1
  • Jun 15, 2021
  • #1
I'm hoping to get someone that has some feedback about my recently purchased 02'.

I bought this car as a project car, and went to repair the A/C. The car had a small hole in the discharge line, so I ordered one, replaced the line, the o-rings, drier, orifice tube, then had the system vacuumed, I checked for leaks and refilled with 34oz of refrigerant. For the first day, the a/c worked perfect, however now I have a super annoying problem where the a/c only works at idle, and doesn't want to work when I'm driving. It continuously cycles warm, then cold. I've noticed that under any acceleration (pedal at 20% or 50%) will cause this warming to occur where the air blows at around 70 degrees. When I let off of the pedal, or slow to a stop the a/c returns to the correct temp of around 40ish degrees.

I have checked the clutch gap, and it is around .020, I've replaced the high and low side pressure switches, verified that the air inlet and mix door isn't blocked in any way and functioning properly. I cannot seem to get the problem to replicate at idle so I haven't been able to use my a/c gauges to see if anything is irregular. I read suggestions of pulling over as soon as the car starts blowing warm to look at the a/c compressor clutch, however, as soon as slow down to pull off the system functionality returns to normal. Upon pulling off I did notice that the line containing the orifice tube was warm, so I re-evacuated the system and installed a new one to eliminate that as a problem.

Does anyone have any suggestions as to how to go about troubleshooting this? Thanks
 

TIGGER

Founding Member
Mar 6, 2000
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Portland, OR
Jun 19, 2021
#2
  • Jun 19, 2021
  • #2
Interesting problem you have. Sounds like something is happening with the compressor above idle. That is the only thing that makes sense to me. If the compressor is not turning you are not going to have Cold air in my opinion. I would hook up your gauges and run the car at idle. If and once the ac is working properly I would wedge something in the throttle body and bring the rpm up and monitor things and see if you can pinpoint what is happening.

The AC pump went out on my wife’s ragtop shortly after we got it. The AC pump would seize randomly. Air would stop being cold. Car would overheat or get much warmer than normal. And then you would smell something burning(belt). I figured out what was happening by doing the same thing I mentioned above.

Hope this helps some.
 

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
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Kearney, NE
Jun 19, 2021
#3
  • Jun 19, 2021
  • #3
Just a different idea in addition to compressor issues. The earlier AC systems have an acceleration cut out switch. I have no idea if it is computer controlled or how it’s handled on an 02, but the compressor disengaging under full throttle is what you describe under any acceleration.
 

KRUISR

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Apr 16, 2015
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Jun 19, 2021
#4
  • Jun 19, 2021
  • #4
I would go with either not enough refrigerant or not enough air flow across the condenser.
 

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
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Kearney, NE
Jun 20, 2021
#5
  • Jun 20, 2021
  • #5
KRUISR said:
I would go with either not enough refrigerant or not enough air flow across the condenser.
Click to expand...
A if there is not enough flow across the condenser, it would be better while moving than at idle.
 

manicmechanic007

5 Year Member
Sep 26, 2017
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Roy, Utah
Jun 20, 2021
#6
  • Jun 20, 2021
  • #6
The WOT relay may be cutting the compressor out. It's the sometimes elusive grey one. It is the wide open throttle cutoff relay. There are pressure charts and compressor on off time charts in the manual for those of you who do not have the cert or recyclers -ie evacuate and recharge capability. You can figure out the charge level yourself without gauges pretty close. I still use R12 in those old ones if they are worth it. It's R1234yf I'm pissed at currently gonna cost me another 10K for a new machine and identifier
 
S

Shelby_GT500

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Mar 28, 2026
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Santa Rosa Beach, FL
Mar 28, 2026
#7
  • Mar 28, 2026
  • #7
Greetings! It’s been a hot minute, but was there a resolution? My sons sn95 is doing the exact same thing. At idle, the AC is blowing cold and under /driving it started to get warm. There are no leaks in the system and the compressor was recently replaced. I did notice that the cluch disengaged periodically when we’re giving it throttle and the ac starts to warm up.
 

KRUISR

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Apr 16, 2015
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Mar 28, 2026
#8
  • Mar 28, 2026
  • #8
On my Escape we had a similar issue where the system would work and then shut down after running for a while. It was due to an overpressure situation in the system. I watched pressures live with Forscan and I could see the system pressure would increase to the point of shutdown. Ultimately the fix was replacing the compressor. Been working great for the last couple years since.
 
S

Shelby_GT500

Member
Mar 28, 2026
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1
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Santa Rosa Beach, FL
Mar 28, 2026
#9
  • Mar 28, 2026
  • #9
We had the compressor replaced and I've checked the pressure with the basic guage from Advance and it's in the correct range. I may just need to take it to the shop again.
 

manicmechanic007

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Sep 26, 2017
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#10
  • Mar 28, 2026
  • #10
Just in case, make sure the cooling fan is going in the right direction
I'd run it at 2000 - 2200 rpm with a gauge set on it for 5 minutes in the shop with a fan on it and see what happens with the pressure
 
S

Shelby_GT500

Member
Mar 28, 2026
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1
13
Santa Rosa Beach, FL
Mar 28, 2026
#11
  • Mar 28, 2026
  • #11
manicmechanic007 said:
Just in case, make sure the cooling fan is going in the right direction
I'd run it at 2000 - 2200 rpm with a gauge set on it for 5 minutes in the shop with a fan on it and see what happens with the pressure
Click to expand...
Which fan?
 

nickyb

I gotta say i never painted my nuts, Never Ever
15 Year Member
Apr 3, 2009
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nevada
Mar 28, 2026
#12
  • Mar 28, 2026
  • #12
The fan on the radiator.
 

manicmechanic007

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#13
  • Mar 28, 2026
  • #13
I had a guy wire an electric one backwards
What happens if you run it with a gauge set on it?
 
S

Shelby_GT500

Member
Mar 28, 2026
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Santa Rosa Beach, FL
Mar 28, 2026
#14
  • Mar 28, 2026
  • #14
nickyb said:
The fan on the radiator.
Click to expand...
Hmm. I just replaced it a couple of days ago. It only fits in one way but that definitely gives me pause. I'll check it out. Thanks.
 
S

Shelby_GT500

Member
Mar 28, 2026
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1
13
Santa Rosa Beach, FL
Mar 29, 2026
#15
  • Mar 29, 2026
  • #15
I checked it and changed the polarity on the fan so now it’s pulling instead of pushing. Hopefully that will fix it. Thanks for the tip!
 
Reactions: manicmechanic007

nickyb

I gotta say i never painted my nuts, Never Ever
15 Year Member
Apr 3, 2009
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#16
  • Mar 29, 2026
  • #16
Hope that does the trick.
 
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