Auto heat part deux.
 

I did a thread many years ago about the auto heat and how it works and what goes wrong. I repaired my ckt board once and it went bad again. Then I ordered a new digital board and it just burned up so I am done with it.
I have thought for a while about just a switch to turn on the heat and keep it original looking without spending a fortune so now I am finally doing it

Biggest problem with this is where to mount the switch.
I finally decided on the left side on the removable cover. I have always left the right cover off so I can feel the arm move and how much it moves. So I will leave it that way.

All you need on the ckt board are the two diodes That are part of the circuit that turns off power to the motor when the arm reaches its limit.
The fan will still have low med and hi speed controlled by the rotary dial.
Low is 1-7. Med is 8-9 and hi is def.
I used a DPDT on-off-on rocker switch. ($26).
Wire the 4 outside terminals in an “X”.
Two terminals on one end goto the motor.
The two middle terminals go to 12v and ground.
All the wires go to the ckt board. I will show you where. Later
I cut everything off the board except the two diodes. I also had to cut the ckt board in half just past the bracket that holds the ckt board in place
I also removed the connectors and wiring that goto the temp sensors and I cut the part of the board off that held the two connectors so the switch would fit.
The way it will be wired up I can have heat without the fans being turned on.

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Ckt board is cut in half
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The temp connectors are cut off along with the wires and terminals that goto the variable resistor. That’s not needed anymore

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It’s still a tight fit

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How I laid out the lines to cut the hole for the switch. Then I put the cover back on and marked the cover and used a cutoff wheel on a dremel.

A little bit about how it works.

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The switch on the right is for low speed fan. The two big wires. The other two wires are for the limiter for the motor. This is the switch that goes bad
All the time but there is a “spare”. The switch under it is the same. Just swap them out.
I think when this switch goes bad the fans run all the time.

The switch on the left is the limit switch for when the heat is turned on.

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The switch at 10 o’clock is no longer used but it just provided a ground for the ckt that acts like a temp control.
The switch at 8 o’clock turns the fan on to medium
The switch at 3 o’clock is the hi speed switch. It provides a ground for a separate relay just for hi speed.

Tomorrow I will finish it.
I need to get power to the switch and trim up the wires.
I have to figure out my connections since I got the switch close to the reostat.
You have to be careful of the emergency brake. I will put the 12v on the upper terminal away from the brake.
I should be able to operate the rocker switch with my thumb.



I hope ����

great idea and very clean job....

Ivan

Thanks for sharing, adding it to my Subscribed list.

Hey Ivan.
I have not been on here in a very long time.
Good to see you are still around

It’s in !!!!
I have heat and now I can even turn it off ….
It’s a bit tight getting to the switch but I have turbo seats.
You can do this with both seats in the car but getting it out may be tough.
I have taken the passenger seat out but that can open an entirely new can of worms getting the bolts out.

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I decided to solder the wires on after I did crimps.

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The clamps that hold the wires didn’t have the rubber on them so I put some heat shrink on there to protect the wires

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You do need to be able to solder.

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The two purple wires are for the motor
The yellow wires is 12v
The grey is ground.
The switch is wired in an “X”. With the 4 outside terminals.
You can connect the purple or motor wires to either end but on the same end.
Power and ground go to the middle two terminals. Again it doesn’t matter.
I wanted forward to turn off the heat or move the arm forward.
I have the right cover off so I can feel where the arm is for how much heat is on and I can verify it is moving. That’s just me.

Just a note.
On the circuit board the two very small wires are for the motor.
Power is red/blk and ground is brown.
One motor connection is obvious the other one is where the two diodes connect together.
You could cut the power wires and connect directly to them but I wouldn’t try that with the motor wires. Way too small.

Total disaster, given how simple the auto heat unit is to fix!

here we go again...i would not expect anything else from loren;-))))))))))))))))

Yann says hello & has a job for you, at his new shop on Sepulveda.

so, he bought out Marcel`s and Robert`s Swiss motors?-))))??
Ivan

Loren fixed my auto heat and it work’s great.

I have fixed mine many times.
I have repaired the circuit board twice. Put in a new aftermarket circuit board that burned up and I have fixed one of the switches.
I have had it. No circuit board other than two diodes.
I have been sideways in my 930 at 120 and there is nothing more scary in a Porsche than the smell of a electrics burning.
There are those that take it out completely and put in the old levers and I considered that but finding the levers and the cost I thought this was better for ME.
I just shared another option.