Automatic Heater Woes

ericheavner · 01-11-2008, 08:47 PM

Hi all,

I have an '82sc with automatic heat problems. I have the single lever heat with the rotary button on top of the control box. It heats up great, but never stops. Heat pours out at all times, regardless of setting. The motor doesn't push the red heat lever back down when I turn it to zero. No matter what setting, heat pours out, frying my little piggies.

I have removed the cover and find the barrel connector intact but OMG at the wires. How do I troubleshoot this bad boy? Can I just remove the entire automatic heat system and put in a two lever control, removing the blower fans, etc. from the engine compartment? How difficult would that be and what problems would it cause?

I've also had a problem with the battery draining overnight, after each drive, requiring a jump start the next time. Could these problems be related?

Thanks a ton!
Eric

javadog · 01-12-2008, 04:10 AM

If I had a buck for every autoheat question I've answered in the last year....

There have been at least two threads in the last week detailing the proceedures for troubleshooting this system, if you want to keep it. If the servo lever does not operate, either you have no power to the system or a dead control unit. The wiring isn't really that tough. You have inputs from two sensors and some power wires. I don't have a wiring diagram handy here at the house, so I can't tell you what color to look for but I'd bet 30 minutes with a meter would answer all your questions.

If the servo operates but doesn't move the lever, the two are likely disconnected. Most likely the valves under the car are rusted and stuck in one position.

You can convert it back to manual control. You'll need the two levers, the shaft they fit on, various washers, nuts and friction discs, two new wires to the valves and a handbrake boot.

JR

Noel · 01-12-2008, 04:17 AM

In the mean time, you can simply remove the small screw that attaches the heater lever (With the red knob on it) to the lever controlled by the auto heat servo motor. THen you can operate your heat manually by raising and lowering the arm yourself, just like with the manual heat cars. The only difference will be that your left and right heat will be controlled together since you only have one lever.

cmonref · 01-12-2008, 04:36 PM

To continue what Noel started: after you disconnect the lever from the servo motor and start to operate manually, the levers will not stay UP -- the springs in the system will return the levers to the OFF position (down).

You could use a small piece of wood with three different dimensions for L, W, and H. (Perhaps 1/2", 3/4", and 1". Pull the levers up and put the wood underneath the lever --- and let the spring pull the lever down to the wood.

Not high tech, for sure, but an effective first step while you plan a more sophisticated solution.

Richard Burns · Richard Burns's Garage

Try getting under the car and see if the heater flaps are permanently closed (rusted maybe) this will cause the heater to be on all the time. A bit of WD 40 or similar will help to free them up if rusted. If they need replacing then go to our host for the parts.There is a chance that the heater fan is staying on causing the battery to drain. I think you are the first I have heard complain about a Porsche heater being too hot.
Good luck.

Noel · 01-13-2008, 03:57 AM

Quote:

Originally Posted by Brian K. Haggard

To continue what Noel started: after you disconnect the lever from the servo motor and start to operate manually, the levers will not stay UP -- the springs in the system will return the levers to the OFF position (down).

You could use a small piece of wood with three different dimensions for L, W, and H. (Perhaps 1/2", 3/4", and 1". Pull the levers up and put the wood underneath the lever --- and let the spring pull the lever down to the wood.

Not high tech, for sure, but an effective first step while you plan a more sophisticated solution.

Brian,

Actually, the heater levers should stay in the position that you set them, assuming that the friction plates are OK. Mine does without the aid of wood.

javadog · 01-13-2008, 04:29 AM

Quote:

Originally Posted by Noel

Brian,

Actually, the heater levers should stay in the position that you set them, assuming that the friction plates are OK. Mine does without the aid of wood.

The cars with auto heat typically do not have the nut on the shaft tightened enough from the factory for the lever to stay in place against the spring tension of the valves. I've never seen one that would hold a setting. If you were going to run it this way for an extended time, you could just tighten the nut, I suppose.

JR

cmonref · 01-13-2008, 07:41 AM

Javadog: you were right in an earlier post. To convert from autoheat to manual control of the levers, you need a different shaft (common to the levers and the parking brake) plus a couple fo the friction discs. The friction discs do not come with the autoheat.

Tightening the nut on the autoheat shaft does no good. It has a shoulder that prevents compression on the discs and lever.

javadog · 01-13-2008, 09:29 AM

Quote:

Originally Posted by Brian K. Haggard

Javadog: you were right in an earlier post. To convert from autoheat to manual control of the levers, you need a different shaft (common to the levers and the parking brake) plus a couple fo the friction discs. The friction discs do not come with the autoheat.

Tightening the nut on the autoheat shaft does no good. It has a shoulder that prevents compression on the discs and lever.

You have to add a washer to tighten the nut enough to do any good. Although, if it were my car, I'd just fix the thing correctly. I had one of these fail a long way from home on a really cold night. 'Twas a pain having to hold the lever up. Had nothing in the car to prop it in a comfortable position.....

JR

Noel · 01-13-2008, 11:27 AM

I wonder why mine is sticking in place then??? Perhaps I should check my heater boxes during the next few months to make sure that the springs that close them are operating OK. Any other ideas?

javadog · 01-13-2008, 12:26 PM

I'd check the valves first, to ensure that they move freely. If they are fine, I'd then check the sleeves that the cables move in, to make sure they are not filled with dried lubricant or have grooves in them from the cables moving back and forth. Lastly, you could check that the lever, it's shaft and the various washers are as designed and nobody has screwed with them in the past.

Most of the time, the valves are at fault, although I have had to replace the guide sleeves before, too.

JR