Scraping Autoheat.

[rob justice]

Whilst doing a couple of jobs on the Autoheat system had me thinking - it must be one the the most overcomplex systems on the car. Has anyone done away with the Autoheat and converted it an earlier method of heating?
I appear to have a problem with the heat controller and second hand they are rare.
I was thinking of along the lines of the VW Beetle with a simple operating lever to operate the heat valves.
Any thoughts?
Regards
Rob

[cmonref]

Before autoheat, there were levers next to the parking brake that operated the heat boxes. The autoheat just made that automatic. When autoheat is installed, the bolt that mounts the brake handle and the heat lever is different that the manual's bolt, and there is a different arrangement of friction wafers that will either let the lever move freely (autoheat) or will hold it where you move it (manual heat).

Changing the bolt and wafers is easy. Leave the operating lever unhooked from the autoheat, and you can operate the lever manually. Presto, manual heat, but with the autoheat "box" still installed.

[rob justice]

Any idea what year Autoheat was a standard fitting?
I quite like the simple lever idea - I'll have a look at the Beetle arrangement tonight to see if any parts can be swapped.
Looking at the Autoheat and all the complexity involved - what were Porsche thinking off?

[cmonref]

Don't know when autoheat was first offered. It's on my 80 SC. When it worked, it was really good. After it started acting up, I compared the parts breakdowns for the autoheat and manual set up, ordered the small handful of parts (one bolt, several washers and friction wafers), and made the conversion. With the autoheat box still installed, it looks original, but operates manually.

Beetle arrangement is identical, but the parts may be different.

A few minutes with your friendly Porsche parts person with their parts diagrams will net you an order for the right parts and the knowledge of how it goes together.

[Jesset100]

Brian explained it good.
If you do go manual heat their are little springs on the flapper boxes. If you don't take these off it will pull the lever down.

[cmonref]

You don't have to remove the springs on the flapper boxes. With the correct number and order of the washers and friction discs and the correct bolt in the handbrake lever / heating lever mount, the friction overcomes the springs. That's the way Porsche did it for YEARS before the advent of autoheat.

[Noel]

Brian,

Great info. Do you happen to have those part numbers on your receipts? Care to share?

Noel

[bkreigsr]

came std on my 77 930.
PO had disconnected by removing the set screw on the lever.
probably originated on the 76 930
(no other modification required to make mine as manual)

[Mysterytrain]

Can someone tell me more about the various autoheat systems. I think it was an option on my 78sc but in the form of a plastic console with a knob on top that was turned that did nothing more then move the levers up and down. Then I think when the factory went to the footwell blowers there was a version with pull levers and a 3 speed knob on the console and then another version that had sensors on the heater boxes and a temp sensor in the cabin. The finally version is interesting because the control box has some interesting connections. In addition to the sensors and the rear blower and footwell blower connections there is a blower temperature switch { ok, what's that for???} and a white/red wire that goes to the speedometer!

[erobinson]

My car is a 76. It has the dial with the 0-def numbers (not just the three numbers). It has the flapper box temp sensor and the cabin temp sensor. I saw someplace where in the engine bay there is supposed to be a silver control box for autoheat and then another for rear defrost. My car has only one silver box and a standard round relay. The really weird part is, with no blower installed, if i put the blower fuse in, the car switches on. I am seriously considering scrapping my autoheat at this point simply due to the amount of work itd most likely take ot get it operating. Also with the blower fuse out, the speedo doesnt work.

Eli

[cmonref]

Noel,

Well, scrambling thru receipts from 1988, I find that two parts were needed:

Bolt, 911 424 515 00
Lamina, 911 424 735 03

My scanner does not work or I would send you the exploded parts diagram. If someone else posts it, refer to it and do the following:

Disconnect the operating rod from the heat lever, inside the autoheat box.
Remove parts #18 and #20.
Install the new bolt
Put the new lamina between #30 and #24

Now, be careful. This was 17 years ago, and my memory ain't what it used to be. Good luck.

[Noel]

Many thanks Brian. I have the Porsche PET CD so I will post the diagram for others to use when I get home tonight.

Thanks again.

Noel