The Fixer

I have removed my air conditioning and air conditioning related components.
But i do need heat and demisting and kept that part of the system intact.

When i finished up with the modifications last spring and finally removed the
condensing coil, thermo bi-metallic switch (which i thought i could do without) and Interior sensor (for the space to install a oil press warning light) My HVaC controls no longer work as they did (obviously) I didn't care about the AUTO function now that i no longer had AC but would like all else to function (flaps, heater valve etc.)

I thought it would be easier to figure this out but i am having trouble.

Note: My HVaC system worked as it should prior to these final weight
saving alterations a few months ago.

Currently Condition: my fan works only on the high setting, the defrost function works and occasionally the central vent flap will open and close properly and vent fresh air. My heater valve no longer functions and did prior.

I need advise on the correct way to bypass what has been removed (AUTO function) to once again have the heat and fresh air without a lot of fuss (the heater solenoid is not being energized as it should when the temperature control is slid to hot and cold.

Anyway this is a tough one to troubleshoot as my WSM is incomplete.

Again, once the Interior sensor and Thermo bi-metallic switch were removed these issues arose. I suspect i cannot have the rest function normally without these devices in place. If someone out there with a racer has been through this please advise. There are no vac leaks. TIA, Matt

Alan

You should put most of it back - it was a bad idea to remove the auto temp loop mode - it's the only way it works.

Put back the temp loop and you can have it work again. You are confused about the "thermo bi-metallic switch (which i thought i could do without)" it isn't a switch and you can't live without it - if you want to have multiple blower speeds.

It is always best to ask first, can save a lot of work. Closed loop temperature control really has nothing to do with the AC (it works with or without).
Open loop you get no heat or full heat - thats all.

Alan

SeanR

The defroster works by turning on the air conditioning, which pulls the humidity out of the air while giving you heat. Now all you are going to be doing is blowing hot, moist air on the windshield.

The Fixer

Agree that i should have asked, I shouldn't have assumed.

I will re install the thermo bi-met switch.

But to clarify: do you think I also need to reinstall the Interior Sensor to have full function?

I needed the space for the pressure warning light.

Yes i understand how the defroster works.

The AC was removed and never going back in.

It gets very cold here in Philly.

The defrost function would still be as useful for cold weather frost removal.

The rest (fogging) will be done with a cloth like in the old days..

Thanks though Sean.

Alan

You need the interior sensor and exterior sensor.

Alan

Jadz928

Matt, you could go with an early non-AC controller. It's vacuum actuated.

Run engine vaccum to the controller (its already in-cabin), then plumb the controller to the actuators you need, lastly hook up the a cable for manual blend heat... done.

You would have no need for the elecric solenoids to control actuators, or auto temp control.

The Forgotten On

Alan, you don't need the sensors if all you want is full hot and full cold, I have been running mine without them for over a year and have only needed the two extremes.

The Fixer

Great idea Jim, I didn't realize there were non ac controllers for the 928. That is a great idea. (I'd like to use an early steering wheel too)
The solenoids are very expensive anyway, be nice to rid the system of them.
I will look into this idea but it doesn't look like 928 INTL has any early non ac control heads at the moment. Will that be hard to find iyo?

Can you elaborate as to how you made your system work?
Thanks, Matt

Alan

I already said exactly that... if you think full off and full on is an acceptable working scenario then its easy. Remember full on is very hot...

Switching to a manual set up may make mores sense for what you want - but its actually lot of work swapping stuff.

Alan

Jadz928

You could use an AC controller... there would just be a setting that doesn't do anything (or you could use that setting for some other flap config)
Early AC controllers certainly are more plentiful.
I'm glad you like my idea. I kinda liked it too!

The Forgotten On

My system is entirely stock auto climate control although it is an 81 so it has a different head unit and set of vacuum valves ( the odd double valve in the center console).

I just removed the sensors and it works fine, all you would need to do is put back the bimetallic unit inside of the housing and use the econ setting for heat and no heat.

But because mine is the early style auto climate control, I don't have an AC button so I have to set it to auto to get the compressor to work. But you shouldn't need to worry about that.

You would also just need to close the center vent and set it to defrost for your defroster to work with the stock wiring.

The Fixer

Alan is right in that everything seems operational once the bi metallic thermo switch is plugged in. The heater valve also woke up but was either open or fully closed but then stopped working for some unknown reason. Maybe too much fiddling. I removed the marble i had in the heater hose before the valve thinking it may have wedged into the valve but once removed the vac diaphragm still not pulling the valve arm. Look at it tomorrow.

The Interior Sensor does not seem to need to be installed but i will double check all functions tomorrow to confirm.

Love the idea and enjoyed our phone convo my friend! I'd ultimately like to keep back dating the look and feel of my beloved 928!

I don't have an AC button on my early '83 either, it also would kick on the ac in AUTO setting..but my central vent is operational with the thermo do dad plugged in and my fan works properly. Seems all hot or all cold which is fine for me, I've never noticed that to be an issue for this vehicle.
Thanks for your help TFO! -Matt

Alan

Can we please all try to stop calling it that. It's a "Blower Resistor Pack" It has 4 resistors that give you the 4 speeds below max blower speed - the blower runs in all of them.

Without the blower resistor pack you get full on (4) and 4 switch selections that do nothing (0-3)

There is a thermal bypass switch integrated here on the older models - it has absolutely no function in normal operation. Newer versions have a series thermal switch (not bi metallic and also has no function in normal operation) and the newest of all have no thermal switch at all.

It is completely incorrect to describe this as a 'thermal switch' of any kind - since that function is quite irrelevant to it's normal operation.

Alan

AirtekHVAC

Matt, I'll pm you about a steering wheel.....

The Fixer

Alan,

Do not let your head explode!!

But this part #92861610100 (41 on microfiche attached)
is called: Thermo Bi-Metal Switch unless i am confused..

I agree it makes no sense. Thank you again for your help.


On a useful side note:

I was thinking today that 928 owners experiencing hvac control head issues should check the connections at this plug for corrosion.
Same type of connection used in 14 pin and elsewhere, mine had a lot of oxidation on them..

Ron,

Thanks for the offer Buddy.

I hope to see you and #30 soon and get you those manifolds i got taking up space in the garage!