AC only blows out of the defrost....? - Cooling - Third Generation F-Body Message Boards

nelapse · 06-28-2008, 08:47 AM

I know this is default mode for the AC...

I replaced the HVAC controller hoping it would eliminate this but it hasn't.

I suspect maybe the two vacuum lines that run out of the firewall are for the ac... however... where do they go? I hooked them into any ordinary vacuum port but it didn't work out. Any ideas?

thunderstick · 06-28-2008, 02:49 PM

yea, the "connection" on the back of the control valve - you're not getting a good enough seal on it. not enough of a loss to hear a leak, but i bet that's your problem...

nelapse · 06-28-2008, 03:55 PM

And this is the rotary valve behind the HVAC?

thunderstick · 07-02-2008, 07:26 PM

yea, the one that has the multiple vac lines attached to it.

nelapse · 07-05-2008, 03:16 PM

Do can you tell if it is leaking? seems to be fine?

thunderstick · 07-07-2008, 03:16 PM

not really - pretty hard to tell, other than the symptoms you have. some people have tried putting vaseline in the tubes and reconnect it to that valve, but not guaranteed to work. if, or whatever you do/try, make sure it works before you put it all back together, as in stuffing your stereo back in, etc. they just get dry and don't seal very well after a while. if that don't work, you'll probably have to replace that tube harness (pain in the butt), or reattach the tubes individually... lemme know.

Kevin91Z · 07-08-2008, 08:51 AM

The longer of the two vacuum lines goes to the coolant divert valve by the throttle body. The other one goes to the port on the TPI plenum that also goes to the cruise control vacuum ball. On a MAF plenum, one goes to the fuel pressure regulator, and the other is what you use for everything else.