LoveMyBus.com - Here, learning, experience, ya

This 4th of July weekend, my alt light came on '77, type IV, FI, stopped and checked belt. It was there belting away doin' it's job so I figured the old used alternator wasn't alternatin' any more, or the voltage regulator wasn't regulatin'. Then I noticed my blinkers didn't work, no blinkie. Then I noticed I was out of gas, gas gauge wasn't gauging. Weird. Turn on my 4 way flashers Ok got flashie. I think, OK flashers work blinkers don't. WTF. Whip out the Bentley. Gawd I hate electrical. Turn the key to run after disconnecting green coil wire to distributor (don't want to fry my points while troubleshooting) now I see my oil light isn't on nor my alt light. Gas gauge isn't moving either. Try blinkers, I hear one blinkie tinkie sound from flasher relay and the alt light comes on simultaneously. OK weirdness like this usually means a ground issue, right? I've already ruled out the alt and VR as I show 13.5 volts at idle with a VO meter and 12.25 shut off. So I study the wiring diagrams in the Bentley to find what all these dashboard things have in common, Flasher switch looks like the culprit, the flasher switch handles a lot of tasks for the dash board. But they either work or they have fallen apart and don't, mine works and is in good shape. I still think its suspect but I leave it be for now. I have the dash out so I can get in there, and I get a call from Nan at our sammich shop and she needs some produce. Pop the dash in lose and start it up. Oops forgot the green coil wire. Plug that in and start it up. BAM everything is normal, I hate it when they fix themselves. Finish the day with out doing anymore. I didn't install the dash because this little gremlin will be back.

Next morn, on way to the shop Bam back again. Well I know the alternator and VR are doing there thing so I can deal for now but I hate not having blinkers during tourist season.

Next day. I dig in again. I know the idiot lites work on ground not positive, the idiot lights always have power, the sending units complete the circuit to ground. But whats with my gauge and blinkers? They all get their power from the one source, as well as any bus that has working EGR and CAT lights. The power source is fuse position 12. Fuse looks good, give it a spin in the holder to make sure it has a connection check 11 too cause that is involved somewhere in this mess, I think it's the blinkers can't remember. Fuses OK.

So for a test I bring in power from somewhere else. The spade connector that has 2 black wires toward the bottom of the cluster of idiot lights is the power source for the lights and the wires coming out of the bulb sockets are the grounds. When I put the outside power to the cluster all lights work properly and I think I have a hack fix. Blinkers no blinkie, but they light now. So the correct power source is wired to the flasher relay some how and I have to track down the actual problem. Great, what a can o' worms the wires going into the fuse panel looks like. So I start wiggling the black wire trying to follow it and presto lights start working. I'm on the right track! I follow to fuse 12, just like the Bentley said, I love that book. I start tuggin, the wire while watching where it goes into the fuse box, I see the fuse wiggling and my lights going on and off. OK it's the wire connection in the back of the fuse box? No! The fuse was bad! It wasn't blown, the tit on the end wasn't worn off ( they do that ) It had a crack across the fuse link just under the top tit where it goes from being a cap to the narrow band that runs to the other cap. Wiggling the wire opened and closed the gap!

Moral of the story, always check the cheap and easy stuff THOROUGHLY first, when dealing with an electrical issue just replace the circuits fuse with a new one first.

The weirdness in the gauge cluster was caused by the back flow of power from the alternator field/idiot light wire, to power the circuits when they demanded power. Electricity is like water, it'll leak if it can and it's lazy. When you start the engine the power from the cluster tickles the field in the alt to get it working, once it's working it energizes that wire and itself and does not need any juice from the dash. If it needs juice from the dash while running the light will come on. If you get a backflow of juice to power the other circuits in the cluster it has to go through the alt idiot lite first.

Sorry for the long post but I thought you folks might learn something about electrical systems and how they work. I still hate electrical, I can muddle my way through and if you have enough ability to fiddle with FI you can fiddle under the dash.