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Skip

Automatic Heater Challenge

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I've been trying to figure out what could be my problem with my automatic heater. Specifically:

(1) the footwell blowers don't come on at all, but both do function with direct 12V current

(2) engine compartment blower actuates

(3) all connections tested as per enclosed diagram

A couple of questions:

(1) it appears that the additional blower relay under the hood (black round), has pin #85 and #86 reversed as it links to the automatic heater connection between the seats (I'm not sure if this could cause the footwell blower lack of activity or not however

- Wt/Grn wire runs from pin #86 to pin 4

- Blk wire runs from pin #85 to pin 3

As I don't quite understand how the relay is supposed to work, am nit sure if this would be problematic

(2) Not sure how to actually test the expensive little heater relay in the engine bay (with 12 pins) - I see a lot of posts on how to mod it, but can't find a bench test method

Any help would be appreciated.

Thanks

Skip

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To provide an update to this post, I've completed a lot of testing with the help of many on this and other forums. I've confirmed that the control unit between the seats functions a intended, the temperature sensor in the cabin and caloric feeler sensor in the duct function as expected with resistance changing as temperature changes. My initial fault finding identified a problem with the Engine Compartment Controller (small grey relay on the left in the engine compartment). The internal workings were not allowing the small relay (for front footwell blowers) to actuate - they did work when I opened up the relay and manually depressed the relay tab. I was able to find a used serviceable relay locally after some effort. This solved part one of the problem. The second issue, was that the engine blower had also failed at some point, so it was a chain reaction of sorts. I was able to order a replacement motor from Pelican and installed it yesterday. Amazingly enough, all systems now work with only a minor squeal at start up from the footwell blowers. I'll open those up in the coming week to lubricate them again - guess I didn't do it well enough the first time. I posted several of the processes on the Pelican forum as well at the following link, should anyone need to take a look at the overall testing phases.

http://forums.pelicanparts.com/porsche-911-technical-forum/649999-auto-heat-query.html

Thanks and good luck

Skip

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