awilson40

The heater fan doesnt do this ,but when running the AC, the fan 'sounds' like its slowing and the air volume drops off as I approach zero vacuum and build boost.
Is this normal??
Thanks

Brian Morris

I think I noticed a similar thing on my car a couple of years ago. I don't think it's the fan speed changing but more likely one of the HVAC doors moving - they're controlled by little vacuum motors. There's a little canister right behind your battery that's a vacuum resevoir - I think it's supposed to hold vacuum for the HVAC system - since the turbo cars aren't always in vacuum. I think my problem was the little vacuum line to this had blown off causing a little wackiness in the HVAC system.

I may have this all wrong - but I think the issue is probably vacuum related and you may have a hose off somewhere.

--Brian Morris
89 951

awilson40

You could be right, time to dig deeper,
thanks

threesticks1

After I got my car back together I had a choice of which way to install the small check valve in the vacuum line. I chose unwisely and put it in backwards and my AC did what you are talking about. After I turned it around, it worked better but still had problems so i connected up a vacuum gage to the vacuum line after the check valve and found that it was leaking slightly under boost and pressurizing the vacuum lines.

New check valve and the problem went away.

Steve Frew

'86 951 Mostly stock and all fun!

awilson40

Wheres that check valve located???
Is this the one coming off the brake booster vac line? If so...then I've checked that <img border="0" title="" alt="[Wink]" src="wink.gif" />
Thanks