Porsche Repair: 911 climate control problem, haynes automotive repair manual, porsche club of america

Question
1991 Carrera 2 Targa. It appears that the blower fan cuts out
any time the temperature control switch is set above the very
coldest setting. Some warm air comes out of the vents but
without the fan running. Similarly, depressing the button for
front defrost yields forced air for one to two seconds only before
the fan cuts out. I don't know where to start with
troubleshooting nor where to get the appropriate schematics.

It's getting cold around here these days... Thanks.  

Answer
Hi Gary,

The heating system on my 356's is quite rustic when compared to your car.  I wish I could be of more help.  

The research I've done indicates there has been a recall program for your car related to the blower motor and its resistor.  I can't seem to find any detailed write-up on it though.  Also, my trusty how-to manual (Haynes Automotive Repair Manual, covering 911's from 65 thru 1989...their product number 80020 (264)) only shows wiring diagrams thru '85.  The diagrams would likely be very similar to your car, as the heating system is fairly basic in operation and not subject to much change.

For the '85 example, the engine compartment blower is energized by its relay, which takes its cue from the Heating Control Unit.  The notion of the blower "cutting out" would normally be accompanied by a blown fuse.  I'm curious why you don't seem to be experiencing this as well...along with ice cold fingers.

Here are a couple of ideas:  first, I found this article ( http://www.porschenet.com/bruns02.html ) which seems to explore the heater blower problems...unfortunately very little detail is provided for fixing problems.  It might give you an idea.  Also, you might find the local region of the Porsche Club of America helpful ( http://www.pca.org/ ).  I've found owners are usually quite responsive to other owners with assistance.  And Porsche people always like talking about their cars!

Usually, I enjoy the challenge of an electrical problem.  With the information I have now, I'm drawing a blank.  If you have any additional info...or if you find something you'd like to talk about...please don't hesitate to write back.

Dave