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AC fails during long drive


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Hi all, my AC stops blowing cold air, loses air pressure after an hour or 2 of driving. Sometimes it'll shoot out a puff of visible moisture before it loses pressure and switches to warm/hot air. Turning the AC off for an hour or more sometimes fixes the issue. I presume there's still enough Freon because it does cool air for at least an hour. My theory was one of the actuators is failing. Anyone have any thoughts on this?
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This is actually interesting because on hot humid days this happens to me (I think the same thing). On max fan speed (I can hear it going full tilt) but minimal flow out of the vents. I turn off the A/C for about 15 min, then it blows fine again. Always ice cold when it does blow. Only on long drives with A/C on max (coldest temp)

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Happens to me too on long drives when it's really humid AND AC is set to 65. I believe the evap just ices over.

 

 

 

I found that if I set the temp to 67-69 then it works fine without interruptions.

2005 LGT Wagon Limited 6 MT RBP Stage 2 - 248K

2007 B9 Tribeca Limited DGM - 258K

SOLD - 2005 OB Limited 5 MT Silver - 245K

SOLD - 2010 OB 6 MT Silver - 205K

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Do you lose air flow out of the vent? Sounds like the evap might be freezing which shouldn’t be possible unless the evap temp sensor is bypassed or faulty

 

Hi, thanks for the response. Yes, I lose airflow, sometimes only on one side, L or R. It feels like a door closes most of the way and whatever air flows is from the heater or hot outdoor temps.

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I fixed this issue in my wagon by replacing the $6.00 A/C Relay Lower right corner in the fuse box. Think it may have been that bright blue one...?

 

The dealer will have them.

 

 

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Few years back, the AC would slow and stop blowing cold air on a long drive. After shutting it off for a few, it would work fine.

Edited by Max Capacity

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

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I fixed this issue in my wagon by replacing the $6.00 A/C Relay Lower right corner in the fuse box. Think it may have been that bright blue one...?

 

The dealer will have them.

 

Few years back, the AC would slow and stop blowing cold air on a long drive. After shutting it off for a few, it would work fine.

 

 

Older son's 2005 OB had that issue. Symptoms were that the panel would indicate the AC being ON but in reality it would be intermittent.

 

 

 

It died finally on the long drive back home from NH one summer. Fixed by replacing the AC relay as Max said.

 

 

EDIT: you can test for relay working or not. Pop the hood and have someone sit in the cabin and turn AC on/off while the engine is running. With the hood open you should hear the AC clutch engage before the fans kick in. If there is no sounds of AC clutch engaging when AC gets turned ON, the AC relay is faulty.

Edited by SubOperator
Added test procedure.

2005 LGT Wagon Limited 6 MT RBP Stage 2 - 248K

2007 B9 Tribeca Limited DGM - 258K

SOLD - 2005 OB Limited 5 MT Silver - 245K

SOLD - 2010 OB 6 MT Silver - 205K

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This is actually interesting because on hot humid days this happens to me (I think the same thing). On max fan speed (I can hear it going full tilt) but minimal flow out of the vents. I turn off the A/C for about 15 min, then it blows fine again. Always ice cold when it does blow. Only on long drives with A/C on max (coldest temp)

 

Happens to me too on long drives when it's really humid AND AC is set to 65. I believe the evap just ices over.

 

 

 

I found that if I set the temp to 67-69 then it works fine without interruptions.

 

 

Same for me on hot and humid days. Have to turn off the AC and let the fan blow for a bit. Sucks.

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FWIW, I think someone has said in the past there are other relay's in the fuse box that are the same ?

 

If so, you may try swapping that one in.

 

But, again, the new one is $6.00

I seem to recall I bought two of them and replaced the one in the Spec, just because.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

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  • 3 weeks later...
Update, I replaced the relay. (It was cheap enough to try.) I drove 2 1/2-3 hours to go camping, AC worked the whole time. I didn't have it blasting full bore and it wasn't heat wave temps outside, but it works. Will report back if it happens again. Thank you all.
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Wait, You all use your A/C :eek:, I never turn mine on unless it is very hot. Today it is hot and I might have to pick up the kids so it will be the first time using it in like 9 months or longer. :lol:

 

I go windows down, but on a real note I do not dire the car on hot days.

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  • 2 weeks later...
Welp, another long drive on a hot day and A/C failed. I tried accessing the "A/C control system self-diagnosis" mode by turning the car on holding the A/C button and front defroster buttons. Nothing. A few tries, with a few variations, A/C on when I turn off the car, defroster on when I turn off car, the opposite, etc. nothing. What am I doing wrong? It's got to be something I'm missing as I fry in the car. Side note, I installed a P204-uh and GROM Bluetooth adaptor into my 05. Any thoughts?
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May be it's time to let an expert fix the issue.

 

I did have my trusted mechanic service both my cars a few years back. I didn't need any parts, just had the system drained and refilled. Both cars have been fine for a number of summers.

 

It was only $60.00

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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You want to press AUTO and MODE buttons and pass the control tests first.

 

If that all passes, the next step is to press the front defrost and A/C buttons to enter the system level diagnostics.

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