Re: More Notes on HVAC... (archive)

The only time I hear my HVAC pump running is when I don't have the engine running and I operate the HVAC buttons. I have never heard the pump run when the engine is running so I can only conclude that engine vacuum is more than enough for proper HVAC vacuum motor control. I guess I'll just have to disconnect the pump to verify this.

demet

Well i figured out my HVAC problem...I had the blue/black check valve in backwards! Also, the vaccum line connection at the manifold was pretty loose...I think the valve being in backwards for so long ruined it! So I have a new one of those coming.
What I did was replace the hose & spliced in a straight piece where the check valve was....and bingo! All the functions work!
However, and this is where i think i might have had some wrong info, because the check valve is gone, the system looses vaccum as soon as you shut the car off...you can hear it. THis valve apparently holds the vaccum when the car is not running...not preventing hot air from entering the system -- maybe someone can verify. Maybe this will prevent someone from tearing their dash apart!

The check valve is designed to hold vaccuum. I do not understands your reference to "hot air". The internal vents will default to defrost if you have a vacuum leak. Leaks are one of the biggest problems with e23 HVAC systems.

What I was trying to say was-I had seen somewhere someone said to valve was to prevent hot air from entering vaccum system - I was just making the observation i thought it was to hold vaccum, thanks for verifying that.

Follow Ups:

[ Follow Ups ] [ 7-series (E23) Message Board ] [ Msg. Board FAQ ]

Questions, comments, or problems, please visit the Roadfly help desk.