Automatic Heater

My 83 SC has an automatic heater that hasn't worked since I got the car, six months. I think the cables are rusted. How much trouble is it to switch to a manual heating setup and what do I have to do? THANKS

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83SC

I have a 1976 911S that I have done this conversion on. I'm not sure if the setup on your year is the same as mine. It was really easy. On my car there was a dial between the seats that was housed in a black box. Inside the box was a servo motor that actuated the heater lever. There was a small ball joint on the side of the heater level that was attached to the servo motor. If you disconnect the ball joint from the servo motor, try to pull the lever manually. If the level will not move, the cables that run to the flapper valves may be bound up. I actually removed the servo motor/black box completely and replace the heater cables. I used some grease on the cables when I replaced them. The other thing to check in the actual flapper valves. They are located in front of the engine. Follow the flexible hose from the headers/heater boxes to the flapper valves. There was a spring that would return the valve to the open position. Make sure that these springs are still there and you should be able to see the other end of the cable hooked through the flapper valve. Good luck.

Thanks for the info, I am not clear on how you replaced the control levers to operate the heater boxes. Did you just get the two levers and mount them alongside the brake lever or do you have to get a brake lever with the two heater control levers mounted all togather. I think will end up doing the same thing you did.

There was already one heater lever on my conversion. Both of the cables were connected to this one heater lever. Some years actually have two heater levers, one for each flapper valve. In 1976 I think that the automatic heat control was an extra option. All they did was attach the existing manual heater lever to the this servo motor/black box thing. If there is no lever visable on your car, try to remove the black box and find the two heater cables. The servo motor in the black box should be connected to the cables. With a vise grip try to pull on the cables one at a time. They should move freely. When you let go of the cables, the springs on the flapper valves should pull the cable back to the normally open position of the flapper valve(no heat). To make the entire conversion I think that you are going to have to buy a heater level. It is not too bad to install. I think that there is one bolt that holds the heater lever and the e-brake. Remove the e-brake boot and you should be able to figure it out. Good luck.

Thanks alot John, will give it a try.

Thanks for the discussion guys. I'm trying to figure out a similar problem in my 87 carrera wich has automatic heating as well.

The driversside flapperbox cable holder is broken. so I need to fix that (probably by installing a new flapperbox) Also I'm not sure about the automatic heater working at all. Thanks to your input, I now know where to look and what to look for since there is no documentation to be found on this topic.

Let me know how the conversion is going and if you find some sort of difficulty anywhere.

Greetings from (freezing) Holland

Maarten Pop

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PS Should the automatic heater control work when ignition is on and the engine is off?
Or does it only work with the engine running as well?


[This message has been edited by maarten (edited 01-11-2000).]

I have an 87' targa, that I parted out. Very few parts left, but what I do have is the hand brake assembly with the two red handles that connects to the heater valves.I guess you would consider mine being the manual set up.I also have the center black box thing, with control knob, but of course it does'nt have the servo motor.Unfortunatly I do not have the long cables that attach to the heater valves if yours is rusted out.$35 for the hand brake assy with levers, and $40 for black box thing, includes shipping where ever you are. Hope this helps!

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First of all the parts for sale in the preceeding message are a good buy. I bought a manual conversion kit because I didn't know what needed.

I have everything done but hooking the manual heating box up. The manual box has one connector with five wires. They are: light blue with dark blue stripe, brown, black, white with black stripe, and brown with white stripe.

The wires inside the care are first going to the rear of the care two separate yellow wires. There is also a plastic connector with a white and a black wire. I think that one goes to the heat sensor in the flapper box.

The wires headed towards the front of the car is one connector with a bare ground and a white wire. That maybe going to a sensor. The other connector has a brown wire, a bluish wire, and a red wire with a white stripe.

Thanks in advance.

83SC - no heat

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83SC

One of the wires activates the engine campartment auxiliary fan. Somehow you need to have this switching occur when you pull up the handles manually.

Following your interesting discussion,I have another question: Can anyone explain the wiring to the engine compartment blower motor?
I have a '76 2.7 CIS, coming back to Germany after 20 years in Guatemala (!). Unfortunately, someone removed the blower motor and all hoses (I expect no ice & snow in Guatemala). I have managed to reinstall nearly everything using good used parts, but I was not able to correctly fix the electrics. Up to now, I have just connected the blower motor to the fuse box in the engine compartment, blowing air now all the time when ignition is on. The wiring to the heater lever is definitely missing completely.
Any description would be of great help!

THE WIRES ORIGINATE FROM ALL THE HARNESS STUFF IN THE DRIVER'S SIDE OF THE ENGINE COMPARTMENT. IF MEMORY SERVES ME WELL, ITS A TWO WIRE , YELLOW AND BROWN (GROUND) THAT ARE TAPED TOGETHER ORIGINALLY. THE HAYNES MANUAL FOR 911'S HAS A PRETTY GOOD SELECTION OF WIRING DIAGRAMS. IT MAY HELP.

The manual switch heating box I was trying to hook up is for 84 and later models. The switch is for the two small blowers in the cabin. The SC doesn't have any blowers in the cabin. The two yellow wires are all you need to hook up to get the blower in the engine compartment running with the manual levers. They hook on to the front base of the manual lever. The blower in the engine compartment comes on when you lift the levers. The only thing I had to do was splice in a couple more inches of wire so would have enough to reach the front of the manual levers. The yellow wires hook on to the back of the automatic heating unit so they were a little short for the manual levers. This is really a easy conversion if your automatic heating unit is shot. Thanks to all who have been helping me out including Bob I think at Pelican Parts over the last few weeks. Should have heat now as soon as my new hoses get here from Pelican Parts naturally.

Sorry to drag up an old topic.

What is the thinking behind fitting manual heater controls? Is the automatic unit not worth fixing?

Cheers

The auto heating control has a temperature sensor between the heater exchangers and the flapper valve that measures the temperature of the heating air as it enters the flapper box. There is also a sensor in the cabin at the center of the top of the windshield frame that measures temp in the cabin. Those two sensors feed a circuit board in the heating control box which then raises or lowers the heating control lever depending on where you set the manual knob on top of the box.

My unit failed when the temperature sensor at the flapper box failed, about 10 years ago. $229 to replace then, if memory serves. So I disconnected the servo in the control box that controlled the heating lever, bought and installed the bolt and the friction discs that are part of the MANUAL system (that keeps the heating lever in place when you move it). Then put the automatic control box back into place (do not reconnect the servo!) and operate the heating lever manually. The auto control box serves only an aesthetic purpose -- it fills the hole it has been in its whole life!

The heating lever is mounted on the same bolt that holds the handbrake lever. To convert from the automatic control to manual control, a different bolt is required, plus 2-3 friction discs. Less than $10 at the dealer. You will have to find a friendly counter person who will let you study the different setups between the automatic and the manual systems for you to properly list the parts that you need for the conversion.

This all assumes that the cables, flapper boxes, etc all work properly. And it applies up to 1983 911SC's, but not to later models with the fans under the dash.

Hi Brian

Thanks for this info.

One more question - how is the engine compartment fan controlled with your set-up?

Cheers

Phil

The engine compartment fan on the SC's is on when the ignition is on. No way to turn it off.

If the heater fan quits or squeals, just unplug it. Leave all of the hoses hooked up, and you will still have plenty of heat. What you will lose is some defrost capability early in the engine warmup cycle, but after the engine is warm, you'll have plenty of heat. 911's have always had plenty of cabin heat, even before the engine compartment fan was installed. That fan was installed to meet US DOT requirements for defrost early in the engine warmup cycle.


[This message has been edited by Brian K. Haggard (edited 10-26-2000).]

Thanks!

So another 911 quirk - a fan that's on whether it's required or not! :-0

I'm on my 4th 911 and the engine compartment blowers have all worked the same way: When raising the manual levers if so equipped, or turning the knob in cars with automatic control, the fan comes on. In NO case have I seen a 911, correctly wired, with a fan that runs constantly.

Yep, I stand corrected -- the heater blower IS switched by a switch under the handbrake/heating lever boot that turns on the fan. For 18 years with the same '80 SC, I never had occasion to discover that. A quick check reveals that my switch is shorted, so the fan ran all the time! Until it started to squeal, that is, and now it is unplugged. And the heat works fine, still, here in Virginia.

I guess if I fit a manual lever, the easiest option would be to fit a separate switch for the fan?