Electrical gremlin

911buff · 911buff's Garage

I need some advice. I have an electrical problem that I am clueless on. I went to start my '74 2.0 And the fuel pump would not work. Troubleshooting the simple things first, checked the fuses, all OK (including the fuel pump fuses on the relay board in the engine compartment). Good continuity from relay board to pump...just no power. Relays check out, too. So I headed to the fuse panel in the cabin, all in order. But then it blew #8 fuse, twice. So a little more investigation but nothing obvious. Then out of the blue, the gages went dead. The lights still work and the starter works when I turn the key. Just no active gages and still no fuel pump. I have torn the dash apart and can find only one issue. The turn signal switch had to be repaired. The plastic extension that connects the switch to the wiring harness plug was missing. I repaired the wiring but when I went to connect the switch, there are six wires but only five slots in the plug. The wiring diagram in the Haynes manual is less than helpful. If anyone has a lead to a usable diagram, I would greatly appreciate it. But back to my main trouble, I am lost! I pulled the wiring harness plug from the starter switch and jumped the wires. Same outcome. Lights and starter but no fuel pump and no gages. So i assume the ignition switch is OK. Is there something I am missing? Please give me some guidance. I have dealt with some weird electrical issues on my 914s but this one has me stumped. Any help is greatly appreciated!

911buff · 911buff's Garage

An update, I was able to get the fuel pump working and the engine running. However, the turn signal relay comes on as soon as the key turns, even though the turn signal is off. Even with the wires disconnected from the switch, the relay comes on. It blows the #8 fuse almost immediately. When I put a 25A fuse in #8, it stays on but the relay starts to smoke...so something is still really wrong. Likewise, the wiper does not function. The washer/two sweep function is operational, but not the normal functions.
I read the tech forum to replace the column switches but the diagram does not make sense. The stock setup has two separate plug leads from the switch to the harness plugs. They match up. But the matches are opposite of the tech forum. So that diagram doesn't help me either. I hate electrical issues!!! Again, any insight is greatly appreciated!

911buff · 911buff's Garage

Correction...it is blowing the #9 fuse (ventilation fan/horn). So now I am really confused. Thanks!

Dave at Pelican Parts · Dave at Pelican Parts's Garage

One of those fuses powers the gauges, so them dying when it pops is expected. Yup, the wiring diagram says S9 (fuse 9) is what powers them.

A smoking relay has probably been damaged; if the smoke isn't due to the damage itself, it may just be showing you that putting too much current through it is damaging it.

The clicking relay can also be because the handbrake handle is pulled up, or the pressure switch in the master cylinder has tripped.

Fuse 9 powers: The gauges, the center console gauges, the reverse lights, the brake lights, and the turn signal switch.

--DD

911buff · 911buff's Garage

Thanks but that really doesn't help me much. Why is it blowing the fuse? according to my owners manual, fuse 9 powers the ventilator fan and horn but according to the diagram it powers the turn signals which makes sense because the turn signal relay does not come on when the fuse is missing. And is there a diagram to clearly show the turn signal and wiper wiring? Thanks.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

The only diagrams that I know of are the factory ones. They are reproduced in Haynes and on our site (in pieces, but in color).

You can also look through Jeff Bowlsby's site; he has a lot of stuff about 914 wiring and other stuff. 914/4 Tech Notebook

The 73 wiring is not identical to the 74, but some people find the earlier style of diagram easier to read. You might check into that.

Chances are that you have a wire that is shorting to ground--somewhere. In my case, the fuse block itself was shifting because of a missing mounting nut, and one connection on it was shorting to ground. I've also had mis-wired license plate lights cause gauge problems. I've even seen strange problems from putting the wrong light bulb in one of the front or rear turn signal buckets...

Did anyone do anything in particular to the car before the problems started?

--DD