Ducman82

Anyone else have the old manual hvac unit with the vac hoses plugged directly in to the head unit? I am double checking my connections and my brain is not grasping the "on/off" set up in the WSM.......

jwillman

Go to 928 classics site. Jim Dorr has a four page guide on the system with improved schematics and photos.

Ducman82

http://928classics.com/uploads/3/3/4...ac-version.pdf

Ya, my car is just.. ODD. i am missing an actuator, (F in the diagram) and my routing is slightly different. and i have a separate AC button. 81 was a strange year....

Ducman82

here is a picture of the back of mine...... ya, not the same.. LOL....

Jadz928

Jake, I'll ask the dumb question... how is it your 81 has a vacuum HVAC system? I thought only 78-79 was vacuum.

Ducman82

That is a very VERY good question. i have Zero Ideas on why it does. infact, i even have one small little vacuum control solenoid right behind the head unit that seems to control the main center flap and has a small purple/yellow stripe wire going to it from the head unit harness. this manual HVAC makes my head hurt. i need to get a vac hand pump and do some tests.

for example the Red line on the top connection has a total of 3 lines coming off it. in that picture you can see how one is red, splits to green and the just see the connector that splits again, and 2 more red lines vanish in to the dash...... Magical....

if i could find a way to adapt ELECTRIC hvac i sooooo would. I'm not above figuring out the wiring...

Ducman82

did a little digging. so the same RED line that splits up, that same port controls the Center flap (E), Heater valve (W), and via the solenoid when activated, the Recalculation flap (F)....

The Forgotten On

80-82 had a different vacuum setup to previous years. Auto climate control was an option and became standard in 83.

I have auto climate in my 81, but most of the parts cars I have seen of the same year had vacuum. I think it was a $200 option for automatic climate control in 1981.

Early 81 also had a weird air temp sensor in the cabin in that the vacuum motor and temperature sender were one unit and were only used until February of 81 which then switched to the separate motor and sensor units.

granprixweiss928

Ducman, did you ever get this figured out.

I just looked at mine, on my 81, because I have a constant hiss sound behind my dash center console when driving.

My ports look like yours did- with the red T and the green and red hoses. off that red T the red hose goes to a solenoid where the blue hose connects....the blue does not come up to this connection block. mine also has the two open ports upper left as in your picture.

I have no purple hose?

My blue and red hoses run thru the firewall- the the red goes to the heater valve. the white is an actuator just under the drivers side, below the steering wheel, the yellow right behind the radio.

Two short green ones T together and then its open. is this the discharge?

I Mityvac'd all the lines going to the actuators...they all work and hold.

granprixweiss928

All my hvac controls seem to work ok, AC has always been good.

Cruise control however will set ok but not hold speed.

Ducman82

i ended up using pliers to pinch each line. turned out the hiss i had was from the center flap actuator having a leak. if i remember right it T's off the red one.