A strange thing keeps happening with my A/C. After driving on the highway with the A/C on, I’m getting a good strong cold air flow from the vents, but after about 1-2 hours the air drops off. I can turn the fan up to max and still can’t get good air flow. It sounds like the air is just circulating in the air box. It does not come out anywhere. I've tried changing to defrost mode, floor position, no difference. If I stop and let it sit for a hour or so everything works normal again for another hour. Then I’m back to the same problem. Anyone have and ideas?

 

Broken blend door.

 

Or freezing up. This often indicates a charge just low enough to be in the critical range. High humidity exacerbates the situation.

 

Mine had a similar problem with the blower running slower and slower and finally not blowing at all. I could "bump" it with my metal flashlight and that would help for a while. Then it might work fine for a while or start slowing back down again.

The solution for me was to replace the blower motor. 3 screws, plug and play. All good now.

..

 

Classic symptom of the A/C freezing up. Most likely cause from being low on freon. Also helps by not running on recirc for long periods of time.

MikeyB

 

Thanks for the info -- It happens both on recir and normal settings. I thought it might be freezing up. It takes a while for it to start dripping under the truck. I'll have to take it to the shop later to check the freon.

 

I agree on the freezing up, mine did that (scared the heck out of me at first). Turns out I was a 1/2 lb low on refridgerant.

Wasn't there a TSB about relocating the evap temp sensor?
I forget what years that applied to though.

MikeyB, why would it help to not run it on recirc?
Wouldn't running recirculate reduce the humidity in the air therefore less condensation and less chance of freezing?

 

Running on recirc will cause the interior temperature to keep falling and even though the air is dryer it still could freeze up. Outside vent air is much warmer is will help keep the evaporator temp higher.

My truck on recirc gets down to about 38 degrees at the vent (driver side center). On outside air it's about 44 degrees. Ambient outside temp is 95 degrees.

MikeyB