Heater Blower Power

I think I repaired my heater blower motor, but it is not getting power. I think the switch on the handbrake assembly is not getting power. With the key on, and the engine off, it is not getting power. Is the heater blower supposed to work with the key on, and the motor off?

I wish I had greater skill at reading electrical diagrams. In case someone's still reading: it looks like it gets power from circuit 50, a yellow wire that also feeds the starter and the fuel pump relay.

Where is my fuel pump relay (the Haynes really sucks for SCs)? It looks like this circuit si what actually powers the fuel pump while the motor is running.

Wish I knew what all those symbols mean. Many mechanics are no better than I at auto electrical, sadly, but those who do understand it are really helpful.


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'83 SC

Super,

You probably need to check fuses #22 and #23 ... maybe this diagram may help:

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_Part1-2.jpg

Just for clarification, any numbers adjacent to any device is a 'Terminal Number' as designated by the DIN standard 72552, whereas circuit numbers, or 'track numbers' are located down at the bottom of the diagram, like a footnote ... the only exception is a wire that goes off the page, then a Roman numeral designates which page (sort of) and the Arabic number desgnates the circuit track number where it reappears on the other page.

Back to your heater ... it looks like power for the heater blower relay comes from fuse #22, and the power for the blower motor comes from fuse #23. Looks kind of like some not-quite-redundant NASA circuitry to me, as a fault at either fuse #22 or #23 takes out your heater!

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Warren Hall
1973 911S Targa

Warren is right. Fuse 22 and 23 are piggybacked. The center fuse of the three located in the engine bay is the heater fuse on my 83 SC. Check for corrosion on the ends of the fuse and the socket it fits into. Just got mine going. Clean the socket and put in a new fuse.

Thanx for the tips, guys. The two fuses in question are next to each other in the engine bay and both look fine, but I'll inspect further.

Warren, I can usually find the numbers on relays and such that correspond with numbers on the diagram, and I can see how circuits skip to other pages, like the VI 12 reference just under fuse 22, which goes to a 'test connection' on p. 6.

I thought the Heater Ventilator Relay got its power from above, a system of yellow wires called "50," across the top of the page, like the famous #30, #15 and "X." This circuit goes to the fuel pump relay and the starter, in addition to the heater ventilator relay, and it seems to originate at the ignition switch. This is in contrast to the vision that power for the heater relay comes from fuse 22. Can you look at this and tell me which way to "backtrack" from the Heater Ventilation Switch, looking for power? That switch is not getting power. Thanks in advance, if you find the time.

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'83 SC

Nevermind. Problem fixed. Bad fuse. It's a good thing too, because I have been POOR at understanding what these circuits are doing by looking at the diagrams. So far, problems have turned out to be fuses and relays only. Which makes sense because I've noticed that the wiring harnesses in you guys' cars is pretty high quality.

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'83 SC