84 Autoheat repair or convert to manual

[Inniswhe]

I have issues with my Autoheat and am not sure what to do.

My car was missing the cabin sensor between the visors when I bought the car about 10 years ago. I am assuming a p.o. removed a faulty sensor and shorted the wires to give a full heat demand signal. The car had heat via the 10 position dial but it never backed off ( no thermistor) so it was manually controlled by selecting a dial position. Not great but acceptable.

Now the system only operates in position 10 on the dial with full heat. Every other position blowers seem to shut off so terrible control.
I wanted to properly repair the system and have searched for years for the nla cabin sensor and never found one.
I don't know what to do at this point. I would like to repair the system to at least get variable manual heat but don't know where to start after reading many threads.
I do believe my footwell blowers and rear blower work as they ask come on at position 10. Would this be controller related or resistor related.

If I knew where I could get the necessary used parts for a conversion to manual heat with levers I would be happy to do that option as it may be easier ? Maybe someone has a list of the required parts to source ?

Does anyone have a suggested place to source a compete used manual heat system or have suggestions on where to start with repairing my autoheat ?

Desperate I know but fed up. I have repaired everything on this car needing attention including transmission refresh but this heating system is driving me.
I actually went to a local mechanic , only guy who works in old 911's. He gave me the factory manual and told me to figure it out , as he wasn't interested !

Sent from my SM-G930W8 using Tapatalk

[Jack Stands]

I'd check with DC Automotive or put a WTB ad in the classifieds. There's probably someone that's converted to a track car and has removed the entire heating system. Even so, I really miss the simplicity of the old style SSI heat exchangers and levers to open the flapper valves. Worked without a bunch of relays and blower so, and didn't break.

[Inniswhe]

I am going to do the manual heat conversion. So far I believe I need the manual heat control box between the seats, Double lever assembly, new cables/guide tubes/grommets. Anything else ?

Can anyone who has done this conversion tell me how what the wiring changes will be. I see that the levers have contact switches so they must wire to to something.

Sent from my SM-G930W8 using Tapatalk

[KiwiJohn]

I gave up on my autoheat but I wanted the rear blower motor to work on demand. This is normally switched by microswitches on the servo in the control box. (On my car anyway.) With the autoheat inoperable this blower will not operate.
I traced the wires in the control box going to the rear blower relay in the engine compartment.
Yellow to brown from memory.
I connected these to the 10 position rotary switch using the 2 on/off terminals, (by-passing the rheostat.)
There is also a push rod connecting the servo to the lever(s) This needs to be disconnected at its ball joint.
My car has one lever for the flapper boxes.
For heat...
1. Pull up lever.
For more heat
2. Rotate 10 position switch to its stop to start blower.
Not perfect, but it gives me some control over the system and it still looks stock.
I do not have footwell blowers and I think these use a different engine compartment relay.

[Inniswhe]

There are no levers on my 1984 so I was planning on installing the 2 lever 4 position switch control from a manual heat car. Does anyone know what brings the rear blower on in the manual heat control . I am thinking is must be the contacts in the lever assembly ?

Sent from my SM-G930W8 using Tapatalk

[javadog]

You need to decide whether or not you want to keep the footwell blowers. A 911 can produce enough heat without the footwell or rear blower if you drive it normally. They were originally installed for increasing the heat output if you spent a lot of time idleling, or in stop and go traffic. If your driving is more recreational and your engine speeds are normally in the 2000-3000 range, I don't think you need them.

I don't like the footwell blowers at all, given their propensity to fail, or make lots of noise, and the huge cost to replace them. The rear blower is less problematic, although I don't use one of those either.

If you don't run the footwell blowers, there's no point to the manual blower control. The rear blower can be turned on via switches on the heater levers.

You can run manual heat with either one lever or two levers. You shouldn't need to change the guide tubes when eliminating the auto heat.

JR

[gomezoneill]

Need help with conversion of Autoheat to Manual

and another

Scraping Autoheat.

[Inniswhe]

I have always seemed to need the footwell blowers in cold weather but my system has likely never worked even close to correctly.
Last year I fixed one non functioning footwell blower by installing a new front a/c condenser fan motor I had on hand.
Right now if I turn the knob to position 10 both of the footwell blowers start as well as the rear blower. If i turn it back to 9 the footwell blowers slow down and the rear blower continues for a few seconds and then everything stops.


Sent from my SM-G930W8 using Tapatalk

[javadog]

The problem with an autoheat system, is that it works in stages. The footwell blowers have three speeds, the servo opens the flapper valves to a position determined by the heat level you select, etc. You may have seen situaltions where you had a low fan speed with a large flapper opening, at least for a short while. The only time you might have experienced the full possible heat output would have been with the dial in the Def/9 position. And that's if everything was working.

If you want to keep the footwell blowers, try to find a complete system (including wiring) from a car with the 3-position blower control.

JR

[86 911 Targa]

Originally Posted by Inniswhe

I have issues with my Autoheat and am not sure what to do.

My car was missing the cabin sensor between the visors when I bought the car about 10 years ago. I am assuming a p.o. removed a faulty sensor and shorted the wires to give a full heat demand signal. The car had heat via the 10 position dial but it never backed off ( no thermistor) so it was manually controlled by selecting a dial position. Not great but acceptable.

Now the system only operates in position 10 on the dial with full heat. Every other position blowers seem to shut off so terrible control.
I wanted to properly repair the system and have searched for years for the nla cabin sensor and never found one.
I don't know what to do at this point. I would like to repair the system to at least get variable manual heat but don't know where to start after reading many threads.
I do believe my footwell blowers and rear blower work as they ask come on at position 10. Would this be controller related or resistor related.

If I knew where I could get the necessary used parts for a conversion to manual heat with levers I would be happy to do that option as it may be easier ? Maybe someone has a list of the required parts to source ?

Does anyone have a suggested place to source a compete used manual heat system or have suggestions on where to start with repairing my autoheat ?

Desperate I know but fed up. I have repaired everything on this car needing attention including transmission refresh but this heating system is driving me.
I actually went to a local mechanic , only guy who works in old 911's. He gave me the factory manual and told me to figure it out , as he wasn't interested !

Sent from my SM-G930W8 using Tapatalk

^^^^^
Auto heat replacement thermistors.

pm me as needed.

Gerry

[Inniswhe]

Jacked the car up today ( Canadian Thanksgiving) to have a look at the flapper valves thinking now is the time to replace them. The rivits holding the heating supply duct thermistor rusted off , sensor was hanging beside the flapper valve housing so it would not sense warm air ( assumming it is even functional). Maybe that is why my blowers turn off after a few seconds on partial heat ??
Shoved in back in the hole and will test. If that had any positive effect maybe there is hope to repair the auto heat.
Going to contact Gerry about the cabin thermistor

Sent from my SM-G930W8 using Tapatalk

[86 911 Targa]

Originally Posted by Inniswhe

Jacked the car up today ( Canadian Thanksgiving) to have a look at the flapper valves thinking now is the time to replace them. The rivits holding the heating supply duct thermistor was hanging beside the flapper valve housing so it would not sense warm air ( assumming it is even functional). Maybe that is why my blowers turn off after a few seconds on partial heat ??
Shoved in back in the hole and will test. If that had any positive effect maybe there is hope to repair the auto heat.
Going to contact Gerry about the cabin thermistor

Sent from my SM-G930W8 using Tapatalk

pm sent.

Gerry

[rokemester]

Originally Posted by Inniswhe

Jacked the car up today ( Canadian Thanksgiving) to have a look at the flapper valves thinking now is the time to replace them. The rivits holding the heating supply duct thermistor was hanging beside the flapper valve housing so it would not sense warm air ( assumming it is even functional). Maybe that is why my blowers turn off after a few seconds on partial heat ??
Shoved in back in the hole and will test. If that had any positive effect maybe there is hope to repair the auto heat.
Going to contact Gerry about the cabin thermistor

Sent from my SM-G930W8 using Tapatalk

Careful careful if you go to clean up or replace the heat exchanger control valves. The three bolts are a b)$&@ to get to. Very easy to strip. Beefier bolts would have been nice. Use heat if you can. Just a PITA!!

[Inniswhe]

Originally Posted by rokemester

Careful careful if you go to clean up or replace the heat exchanger control valves. The three bolts are a b)$&@ to get to. Very easy to strip. Beefier bolts would have been nice. Use heat if you can. Just a PITA!!

Yeah the nuts look miserable to get at and pretty corroded /small. I had a look at them and spayed some pb blaster up there to start the process. I am not sure if I will try and replace the valves . Not sure how one can get at the upper nut of the 3. The lower 2, I can probably get some heat on.

Sent from my SM-G930W8 using Tapatalk

[930cabman]

Better get moving with this project, it was 38 degrees (abt. 3 in your neck of the woods) in Buffalo this morning. Our '87 cab suffers the same issue but I have never gotten into it. Good luck with the repair and keep us updated with your progress.

From where I stand it looks like another great German design???

[CCM911]

Gerry - Where do those Thermisters go? Is this a common wear part?

[86 911 Targa]

Originally Posted by CCM911

Gerry - Where do those Thermisters go? Is this a common wear part?

This is a replacement part for the cabin temp sensor
located between the two sun visors.

Google "Thermistor" and the correct p/n.

Or, call the mfg @ 1-800-4-newark.

Or Electronic Components Distributor Newark element14.

I don't have any of these.

The pics I posted are from my P-Car reference folder.

Best,

Gerry

[86 911 Targa]

84 Autoheat cabin temp sensor
^^^^^
Here's a bit more help.

Also, do a search-thermistor, lots of help there.

Gerry

[rokemester]

Originally Posted by Inniswhe

Yeah the nuts look miserable to get at and pretty corroded /small. I had a look at them and spayed some pb blaster up there to start the process. I am not sure if I will try and replace the valves . Not sure how one can get at the upper nut of the 3. The lower 2, I can probably get some heat on.

Sent from my SM-G930W8 using Tapatalk

Heat, heat, heat! Acetylene torch, white hot the only way to go. I wish I had a proper torch. I have a suburban variety with small canisters. The third bolt can be accessed with a flexible extension.

[Inniswhe]

A few years ago when I was doing some work under the car . I looked at those heater valves. They looked pretty corroded so I sprayed them down with wd40 or something similar to try and slow the inevitable corrosion and try and keep things from seizing.

When I checked those nuts tonight after spraying with pb blaster last night , all six loosened easily so I guess I got lucky. Never had to turn on the map gas.

Sent from my SM-G930W8 using Tapatalk