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Need Help w/ Vacuum or AC Duct Problem

tperk100 on Sun July 24, 2011 10:51 AM User is offline

Year: 04
Make: Ford
Model: F350 TD
Engine Size: 6.0
Refrigerant Type: 134A
Ambient Temp: na
Pressure Low: na
Pressure High: na

MAX AC is on. After shutting down my truck for a few minutes, and then re-starting it, the MAX AC air is exhausted through the DEFROST duct. After about 5 minutes of driving I can hear the ductwork damper(?) straining but moving into what is probably the correct position. The AC seems to be working correctly as it blows all air out of the AC registers at this point.

What is perplexing me is that the thing starts to work correctly after a few minutes. If the vacuum or the damper were defective, you would think it would be that way full time.

I suppose I could start by asking how the AC duct system USED to maintain the damper position when things were working right. Is there some sort of vacuum reservoir that should maintain vacuum with vehicle shut down....therby keeping damper in correct position?

Any other thoughts / suggestions?


Tom P

mk378 on Sun July 24, 2011 11:38 AM User is offline

Almost everything that late model uses electric actuators, not vacuum. You will also likely be dealing with a CAN bus.

Especially considering it's a diesel, so the engine isn't usable as a source of vacuum.

Edited: Sun July 24, 2011 at 11:39 AM by mk378

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