seat belt and ignition shut-off?

[L Sjoberg]

I just bought a '74 1.8L. Apparently it has a system that prevents the car from being started w/o the seat belt on. The car shut down on me this a.m when I tried to start it BEFORE putting the belt on. Unfortunately, it won't crank now. The battery is fine, but no juice - no radio, lights, turn over; etc. Can the shut-off system be manually reset? And on another note, can it be bypassed altogether? Is there anything else that could have caused the car to just shut down? I'd like to drive the car north this weekend, and tuck the 911SC in the garage : )

[Dave at Pelican Parts]

The Infamous Seatbelt Interlock relay is located under the passenger seat.

To temporarily disable the system, you can trace the wires from the seat belt receivers. They'll come to a connector, which you simply unplug.

That still leaves you vulnerable to a failure of the relay or socket. Which means that you need to watch out if you ever get water in the passenger compartment.

A more permanent fix is to find the two big yellow wires that go to the relay socket. Cut them off before the socket, then use a crimp-on connector (or other connector of your choice) to hook them together. Shrink wrap on the join is essential--you don't want water getting into the connection and corroding it.

I don't think the relay will affect the radio, lights, etc. If you aren't getting any of those either, your problem is most likely somewhere upstream of there. Check your fuses (they can look good even when they aren't).

The ignition switch may also be going bad. Try wiggling the key a little bit.

To really start troubleshooting, though, you'll need a wiring diagram. Go out and buy a Haynes manual. Get it from Pelican so that they can keep this website running. Haynes has the next best thing to the factory color diagrams. (Which I hear will be posted up elsewhere on the site shortly, YEAH!)

Good luck!

--DD

[L Sjoberg]

Thanks, Dave - I think I've narrowed it down a little further now : ) I got the seat belt wires disconnected, and was able to get the car started w/ a jump. Battery was still registering at 14V, and everything came on. I checked the fuses, and replaced the low beams left fuse. After letting the car idle about 45 sec., I tried the lights and the car shut down again. I checked the wires for the lights on the passenger side (the one that had the bad fuse), and the white wire is cut in two : ( Could this be the ground for the headlights, and would this short the system (ie: could the bad ground at the headlight shut the car down when I try the lights)? This may or may not be a silly question, but I'm notoriously bad w/ electricity...

[L Sjoberg]

At the risk of writing a book on this dang problem...

I fixed the wire issue up front - car started w/ a jump again, but ran erratically on its own. I swapped the battery from my SC, and everything worked except the ignition - the starter isn't turning over, not even a "click" from the coil. At the very least, my guess is the battery is no good, after all. Before I swap for a new one, though, is there something else I should look at?

[JP Noonan]

The white wire cut in two is not a ground. Porsche uses brown as the ground wire. Try honking the horn and putting the lights on. If the lights are bright and the horn loud (as with everything on a 914 "loud" being relative)then the batt is OK. My guess, as has been suggested, is that the ignition switch is bad, they only cost about $15 and fail all the time, not worth having a spare, but if the car has an original switch then...
My '74 had already been hacked up, and the seatbelt interlock relay was replaced with an open terminal block that has to date started one car stopping short (stopped dead going 85-90 MPH, alt. light came on, nothing else elctrical worked, stopped, pulled neg. teminal found short by following SMOKE, and started right back up) and an intermittent oil pressure light. So follow Daves advice and crimp the wires correctly. One thing to add to Daves directions is to strip the wires then scrap them until they are shiny. Another test is to short the starter out to the batt. This involves either bypassing the plug at the relay board or crawling under the car. If as you say you are not comfortable with 12 volt systems then buy a test meter and trace the ignition circut through the car before tring to "hot wire" anything. See if +12V makes it to the switch then see if it makes it to the starter.

[Dave at Pelican Parts]

Jim Thorusen has a nice article on the starter system. Check under the Tech Articles section of this very page. He can get you pointed in the right direction.

--DD