Weird AC problem

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Echomirage

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when running the AC, after about 30min of driving, i will suddenly get very little airflow out of the vents. i can blast the fan speed, turn all the vents but 1-2 off, either on recirc or fresh air, and nothing more then barely a sneeze comes out of the vents. the fan is running on high, still cold air, but almost nothing coming out.

ill then hit the AC button off, let the vent blow, and itll return to normal. i then have to turn the AC back on, and so forth every 20min or so.

it only seems to do this while on AC, not vent.

i replaced the blend door actuator thing, down on the floor under the dash, and had a shadetree mechanic replace the actual blend door itself, and i still have the same problem. im actually thinking its a vacuum issue? possibly a leaking vacuum canister or line?

anyone have this issue or an idea on whats wrong.
 

east302

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It is probably ice accumulation on evaporator core, blocking air flow. Check to see that the condensate drain (passenger side firewall below the heater hoses) isn't clogged.

Not sure what causes it, but have read where some said it was a system pressure issue or bad cycling switch. An a/c shop could probably figure it out.



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Bob L

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An easy thing to check is to remove the blower motor and make sure there are no leaves in the evaporator case. With the motor removed look to the left and you can see the evaporator, it should be clean. Then reach in and feel the bottom of the case for leaves that can blow up and block the air from going through the evaporator.
There are several videos on You Tube showing how to clean. It can be pretty crappy in there and cleaning can make a big difference. Mine was very dirty.
 

chipskittles

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Agree on the evaporatator core freezing. I've experienced the same issue on long trips. Cheap thing to try if you have already checked for debris in the evaporator and verified the system is charged properly is a new cycling switch. A quick test of the cycling switch: Start vehicle and put AC on, and run it until inside is pretty cool. Then put the air on recirculate and drop the fan speed to the lowest setting. After a few minutes the compressor should start cutting off every couple minutes or so. This happens because the load on the system drops, so the refrigerant is not absorbing as much heat, so the pressure goes below the threshold for the cycling switch and cuts off the compressor until the pressure goes back up, then it kicks back on. This is what it's supposed to do. If it just stays on and never cycles the evaporator will get too cold and it will start freezing up.

I spent the money on an AC Delco cycling switch after figuring out the part store switch never worked right. No freezing up since.
 

east302

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Is that the switch on the accumulator?


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east302

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