Along those same lines, if you have a 74 or early 75 Super Beetle (and maybe others, but this is the only place I've seen them), a big source of starting problems in the seat belt interlock relay on the back of the fuse box. This has to the most over-engineered idea VW ever put in one of their air-cooled vehicles. There were contact switches in the seat cushions and in the seat belt latches. If there was someone sitting in the seat, the seat belt had to be latched in order for the relay to kick in. The ignition wire that already goes from the battery to the fuse block to the ignition switch and back to the starter was fed through this relay. The switches in the cushions have long since bit the dust and the system has to be by-passed. The way I've seen it done most often was to wrap a piece of wire around the ignition wire in and out terminals on the relay and then plugging it back in the socket. That works for a while, but it'll make you pull your hair out (I'm living proof!) when the wire gets covered with corrosion a few years later. I can't tell you how many good switches and starters I changed out before I figured out what was really wrong with Joy's 75 convertible! :-x
Once I figured out what the problem was, I pulled the relay out, pulled all the wires out of the fuse block that went to the realy, and removed them all the way back to the seats and seat belts. Then I took the big heavy wire that from the ignition switch and the one going back to the starter, cut about a foot off of each of them, slid a piece of heat-shirnk tubing over one, soidered the ends together and sealed the connection with the heat-shrink. It shortened the circuit by about two feet and eliminated 2 push-on terminals and two home-made wire wrapped connections.
Again, I don't know what other vehicles may have them, but if you have intermidant problems with the starter not kicking in on 74 or early 75 Super, this could be the source of your problem.
