924Board.org

[!tom]

I'm in the process of making the heater work in my car.

The motor was a melted mess when I pulled it out. It hadn't worked for some time, and I knew the blower didn't work when I bought the car.

I re-wired the motor and got it running again on my workbench, and now it's time to reassemble everything. I was somewhat perplexed at the fact that the motor had provisions for 3 speeds, but the controls looked like they only would provide 2 speeds plus off. It also looked ilke the A/C switch controlled the same motor, and may provide all 3 speeds. I'm in the process of removing A/C components (something the P/O started), so I had not intended on putting the A/C switch back in.

So, I hit the Haynes manual wiring diagrams to sort out how to get power to the fan upon reassembly. I see that it uses the A/C relay; mine consists of some broken plastic pieces where the relay is supposed to mount.

Looking at page 267 of the manual, it looks to me as though to restore function to the heater fan switch on the dash, I would connect the brown wire in current track 5 to the gr/bl wire in track 13, bypassing the non-existant relay. I can only assume that S19 will interrupt power to the red wire in track 14 when the key is off.

However, if I do this, it appears as though the fan will ALWAYS be on, powered through resistor N23, presumably at a low speed, especially since the brown wire on the blower fan is connected through a 15 or so ohm resistor. The console control will power the fan through the 0.75 ohm resistor (which I replaced, since it had turned into a puddle except for the resistor element), and no resistor at all.

So, is this right? Is the fan supposed to be ALWAYS on when the car is running? It appears as though I can disconnect one terminal of the plug T2c to get the fan to turn off, if I need it to.

Am I reading this right? Is this really how its supposed to work?

If S19 doesn't interrupt the power when the car is on, then I don't see how the fan ever turns off without a relay.
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78 924 NA
5-lug

[-nick]

The later heater fans (late '82 / early 944 / 924S) are always on at low speed while the car is running. Porsche justified it as wanting to keep fresh air flowing in the cabin at all times. I think it was designed to help with the moldy smell that accumulates in these cars from battery tray leaks.
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

[!tom]

[-nick]

Good call, almost forgot about that
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

[Paul]

Or could it be some Germans wear the same shirt to work all week?
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.