Hi all,

Well, although I had thought I had all my vacuum issues with my HVAC figured out, last night on both legs of a 60+ mile round trip at highway speeds my air delivery for my HVAC system (Auto-Climate control) would spontaneously switch from defrost to the AC instrument panel vents. I had my OBD gauges set up to monitor the MAP pressure and I did not detect much of a change when this would happen as I was traveling at constant speeds on the flat. Changing among the different air delivery options seemed not to make a difference.

Last fall I replaced my under-hood vacuum hoses and used my Mityvac tool to check the individual lines. I thought I had it all fixed but I do remember that there could have been a slight leak at the one component I was never quite able to eliminate from being a source of the leak: The vacuum control assembly. (#5 in the diagram below)

Before I spend the money on this part, is there anything else I should check that could be the culprit?

Thanks

 

I have a similar problem Christine. Intermittently my vents will change while under load. My lines under the hood are new. I saw a post (can't remember from who) saying that their vent select switch was bad. I am curious to see what you find as a fix for yours.

 

Thanks for the confirmation that that same symptoms can occur with new hoses. I'll keep people posted.