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944 1986 - heater on hot tried all usual stuff (Read 674 times)
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944 1986 - heater on hot tried all usual stuff
Oct 30th, 2018 at 6:35pm
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My heating is driving me nuts right now (1986 2.5 lux) with being on hot the whole time!

Ive gone through the system as best I can and worked out the following:
- tested vacuum valve in engine bay - works fine if I suck on it or if I bypass the internal - pipesĀ and hook the brake vacuum directly to it
- swapped out both solenoid valves under dash
- swapped out heater control unit with a 2nd hand one and now when I hit the recirc button I can feel the rear solenoid work and recirc circuit works properly
no matter what I do with the heater knob it just blows hot air constantly - solenoid doesnt feel like its switching at all

I realise the system defaults to hot if theres a problem. All vacuum hoses seem to be ok.

Only thing I can think is that the heater rheostat is broken on my new 2nd hand heater control unit - Ive tried 3 now so would be d**n unlucky if I had 3 failed units? Either that or theres no +ve feed coming in to the rheostat that should then go out to the solenoid when the temp control is set to cold? As far as Im aware there are no hidden fuses anywhere to check?

Any help appreciated as Im not sure what to do next and cant afford to keep buying heater control units!

944 2.5 Lux 1986
GAX coilovers, cup II wheels, 186k drives like new!
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Re: 944 1986 - heater on hot tried all usual stuff
Reply #1 - Nov 2nd, 2018 at 7:28pm
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have you looked at this VERY common problem

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