dprantl

Ok, so on my '91 GT the recirc flap stays open when the climate control is set all the way to the left (on the "O"). I was looking over the manual, and all the pictures seem to indicate that this symbol is supposed to be like an "O" but with three circling arrows instead. So I tested the black vacuum line at the brake booster that goes into the firewall and it held vacuum just fine. Questions:

1) Do older 928's have climate control heads that open the recirc flap when they are set to the "O" position? I know my '86 does recirc with the climate control off.

2) If 1) was yes, does my GT have an older climate control head that was at some point swapped in since it has an "O" instead of the circling arrows?

3) Could there still be a problem with one or more of climate control vacuum actuators (or one of the solenoids themselves) even though the black vacuum line holds vacuum?

Dan
'91 928GT S/C
'86 928S 5-spd w/LSD *sale pending*

RyanPerrella

in 91 the head unit changed to include the recirc IIRC

dprantl

Are you sure, because my '86 definitely has recirc with the climate control off.

Dan
'91 928GT S/C
'86 928S 5-spd w/LSD *sale pending*

RyanPerrella

the feature maybe the same but the labeling is different.

RyanPerrella

if your 91 dosent have the circling arrows it is an older unit, wether thats just labeling or something different i dont know. I think there is something different with the unit itself but i dont know.

the flyin' scotsman

From the '91 Tech Spec:

IcemanG17

The head units did change in 1991.....the old style was the "off" postition at the far left....in 91 they changed that to the recirculation (3 arrows in a circle) position...

It is VERY likely that you have a leaky recirc acutator... a bit of a PITA to replace, but well worth it if you live somewhere hot like me!!

RyanPerrella

Question

Where is the actuator that controls the off portion of the <90 head unit. When i have my switch set there, i get a weird almost electrical motor noise from somewhere inside the dash and its annoying. I nearly have my dash apart and wouldnt mind replacing it if its easily accessable with how far into deconstruction i am currently in.

Alan

There is no single Off actuator - each of the slider positions is mapped to multiple flap positions.

Alan

dprantl

Hmm, if the black vacuum line that feeds all the actuators holds vacuum, would that not mean that I cannot have a leak in any of them?

Dan
'91 928GT S/C
'86 928S 5-spd w/LSD *sale pending*

Alan

No - you need to test for vacuum on that feeder line in all the modes of the control unit (every slider position) to know if there is a leak. If a solenoid valve for an actuator isn't open you won't know if there is a leak beyond the valve.

Alan

the flyin' scotsman

The black line supplies vacuum for the HVAC system..........the head unit distributes this vacuum to accuators via electrically switched solenoids.

Test for vacuum at the black line at the HVAC vac distribution point; engine running. After confirmation test that all actuators hold vacuum; these are normal source of failure.

If you have vacuum and all actuators test good but still have an issue there may be a problem with a solenoid(s) or the head unit itself.

John Pirtle has a great write up: http://members.rennlist.com/pirtle/svc.html

IcemanG17

Dan
Review Pirtles (above) or Tony's write ups (928intl has links) about the system as a whole.....

I am nearly 100% sure that your recirc flap leaks...its the blue line on the solenoid behind the stereo....Rich and I replaced ours last year...but I can't find the link?

dprantl

Yep, that's what it is alright. I looked under the dash on the passenger side and saw that at full cold, the flap was all the way down. I prodded it a little and it moved slowly up until it was about half-way up and stayed there. Anyone ever R&R'ed the recirc flap on a dual-airbag car?

Dan
'91 928GT S/C
'86 928S 5-spd w/LSD *sale pending*