AC vents

[jsloden]

Have a bit of a weird problem. I can drive my car around with the AC on full blast and for about 10-15 minutes and it's fine. After that the main vents in the dash seem to open and close. At first I thought the actual blower was going out but that doesn't seem to be the case because you can still hear it going just fine. But it's like it loses vacuum and the vents close for 10-15 seconds then open back up. It will start doing this more and more frequently the longer I drive. I took a 45 minute drive the other night and was sweating before I got out of the car.

Thanks

[David T]

It could be the evap coil is icing up. Probably low on refrigerant.

[jsloden]

I had the amount checked. It was fine. It seems as if the vent is actually closing. It's like it's losing vacuum. I know the rest position of the center vents is to be closed so it would make sense that if it loses vacuum then it would shut. Does anyone know where the vacuum line that goes to the ac knob hooks up to the engine?

Thanks

[David T]

If it is the vent closing you should be able to see the actuator moving. Does your mode switch hiss? If it does then it is leaking and needs to be rebuilt.

[TTait]

I have a similar problem. Low airflow from center vent under acceleration.

I have just carefully rebuild and reinstalled my AC box. looks to be in good repair, nothing is broken, everything seems to be hooked up correctly. I just rebuild my mode switch. I don't think there are any vacuum leaks - either in the cabin or in general. Obviously however something is wrong.

I usually run the AC in max mode, and get excellent airflow from the center vent at idle or when cruising. Under hard accelerations however I lose airflow from the center vent. When I let up on the accelerator, the airflow returns immediately. I believe this means that when I have high vacuum, a flap is moving and cutting off airflow.

This was also happening before I did my recent round of work, before rebuilding the A/C Heater box and the the mode switch and before tracking down a few vacuum leaks. It could mean something was hooked up wrong before and I left it hooked up incorrectly during my work, but I tried to cross reference diagrams and didn't notice any discrepancies.

I feel like I've seen this condition mentioned in the forum before, but the search function here is kinda awful so I apologize for likely repeating it.

[TTait]

Looks like I found the answer:

http://dmctalk.org/showthread.php?14...s-off-A-C-fans