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Registered User
Join Date: Nov 2007
Location: chicago
Posts: 16
electronic heater controll unit fix? 86'

I get some very bizzare behavior out of my 911's heater system. Truthfully i'm not even sure how it's supposed to operate when functioning properly. All troubles seem to originate around the electronic controller in the center console. the footwell boosters run intermittently but in unison which omits bad blower motors. I have never heard or witnessed the engine compartment booster blower run. When I play with the thermostat setting sometimes it kicks the footwell blowers on and other times it does not. When working defrost setting runs them at full power 9 knocks it down a bit 8-7 runs the motors slowly with no change in output 6 and below nothing ever! even stranger I can often get the foot well blowers going by goosing it off an idle, almost like a voltage spike gets things going again however the run is always temporary and it shuts off and on again intermittently. I have also noted that cold temps initially seem to help operation. This I have to say this is with out any doubt the goofiest system i have ever run across. The servo driving the flapper functions fine all other blowers operate my suspicion is the temp sensor, relays, and or the main engine compartment booster motor having some effect on the system which i cannot confirm it's functionality. Where do i start? is there a way to simplify or even eliminate this overly complicated system? I thought i could read wiring schematics until i saw these. I would really appreciate any info. or a direction in which to start. mods etc.

Old 11-24-2007, 10:43 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Join Date: Jan 2004
Location: Pittsford, NY
Posts: 3,406
search for user 'mysterytrain' and you will find plenty of threads on this subject. Search function is upper right. Select advanced search and search his name or 'autoheat' in the subject.
Tony G.
2006 Cayman S
1973 914 1.7 project
"Rules are for the interpretation of wise men and the obedience of fools." Colin Chapman, Founder, Lotus F1
Old 11-24-2007, 11:05 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Join Date: Apr 2005
Location: In the wind...
Posts: 28,552
Some of what you describe is the normal functioning of the system. I'd start with reading the owner's manual, to get an idea of what the various settings do, and then read the umpteen posts on Pelicam about this.


Old 11-24-2007, 11:13 AM
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