TheSamba.com :: View topic - Your thoughts as I continue to diagnose (electrical)

Sun Oct 18, 2009 2:31 pm

Well, here is some info and maybe someone can chime in as I continue to try different things.

Started with my new bus, 79 federal, which I picked up after 4 years of sitting. I've been doing a lot of mechanical, but mostly I've been working to get her back to running good order.

As far as the electrical goes, it started with a short somewhere. When I got a new battery and hooked it up the parking lights immediately came on. Everything seemed to work though- headlights, blinkers, hazards, brake lights.

This may be a stupid question, but how do I get the dome light to come on?

Anyway, I did some research on here and decided to replace the hazard switch and at the same time replace the headlights switch as well. I also cleaned all the wiring that was nasty for the switch plugs. So now the symptoms seemed to have changed and I'm gonna run through this the way it happened because it might be important.

First I hooked up the battery. I was excited because the short seemed to have gone away and I thought it was fixed. Next I installed the hazard knob and when it got close to being tight I saw a small spark. As I played with the blinkers I noticed that they are now not functioning properly. When I toggle the switch, I can hear the flasher relay making some weird buzzing noise. This is for either blinker. I then noticed that the drivers side headlight went out in this process (it worked only a couple weeks earlier when I installed the conversion kit) but the high beam still works.

I disconnected the battery again and put the original switches back in. BTW both switches came from Bus Depot.

Now it works like this. The blinkers will work, but I have to play with the switch a lot and hear the buzzing from the flasher relay. The drivers headlight is still out. And the parking lights still come on without using the headlight switch, only this time they only do so as soon as I put the key in the ignition.

I should mention that the horn doesn't work either, but I'm not sure if it's related.

I've been trying things, but to no avail. Next I'm gonna try to match up the wiring diagram with the bentley for the fuse box.

It doesn't look like the PO messed with too much. There are stereo wires dangling, but thats it. I think that is a good thing not having to mess with someones jerry rigged system. I'd like it to just work. Especially the headlight, I've already gotten a fix it ticket.

BTW, the main positive battery cable, the ground battery cable and the tranny ground cable are all new too.

Thanks to any that offer ideas.

Sun Oct 18, 2009 2:54 pm

Check all grounds. When a ground is lost, the power will try to go other places. this can lead to some very interesting relsuts. So, clean all of the grounds and then see what happens.

Sun Oct 18, 2009 3:00 pm

Are you matching the wire colors to the terminal numbers on the switches exactly? or just swapping into the same locations on the other switch?

Mon Oct 19, 2009 12:44 pm

Checked the wiring behind the fusebox and it looks clean and factory. Are there only supposed to be 2 relays?

I also removed all the stereo wiring from the PO. The only one left is the blue wire that was hooked up to radio power.

When I changed the switches I matched the numbers from the old switch to the new switch. Currently the old switches are in.

Also, on the headlight switch when I installed the new one it is not the same switch. What I mean is that there is a metal type washer that holds the switch to the dashboard (not sure if there is a name for this) and the one from the old switch is not the same size and thread pattern.

Anyway, I also checked the bulb and its fine.

When I rotate the headlight knob a little with the headlights on, the R headlight flickers.

Mon Oct 19, 2009 4:09 pm

ranzuo wrote: Are there only supposed to be 2 relays?

Yes, and a tiny one a little bigger than a sugar cube, that's the door buzzer, if yours is gone it's not a big deal.

Quote: When I changed the switches I matched the numbers from the old switch to the new switch. Currently the old switches are in.

But did you confirm that each color wire was on the correctly numbered terminal as stated in the diagram?? Never trust a PO's wiring.

Quote: Also, on the headlight switch when I installed the new one it is not the same switch. What I mean is that there is a metal type washer that holds the switch to the dashboard (not sure if there is a name for this) and the one from the old switch is not the same size and thread pattern.

No biggie, different manufacturers may use different threads on the nut. Where'd ya get he switch?

Quote: When I rotate the headlight knob a little with the headlights on, the R headlight flickers.

Now that's odd because if it was wired properly both may flicker (although they shouldn't) as the circuit doesn't split until the fuse box, once again, where'd ya get the switch?

Mon Oct 19, 2009 5:21 pm

The switches are from Bus Depot and do not match the part numbers exactly, but are the ones that say are correct.

I'll have to go over and match the wires to the correct numbers on the switch with my bentley.

Did you happen to know how to see if the dome light works?

Also, when cutting out the radio wires the PO had a wire connected that I don't know if it's supposed to be ground or power. But the wire is the black wire that runs to the rear defroster. The rear defroster switch seems intact, as well as the two wires that run to it.

Lastly, you say it's ok that the switch is different as far as the washer that connects it to the dash, but then how do I connect it? Otherwise it's just gonna hang there cause I have no other way to secure it to the dash.

Thanks again.

Mon Oct 19, 2009 7:55 pm

Ohhhh....You didnt say the switch wouldn't fit the hole :shock: Electrically most switches are the same but your issue is something you need to take up with Ron and see what he proposes to do to make it right. Unless you got a deal on something that warned you of this in the description.

The rear defog is supplied with keyed power by a black wire, there is also a brown ground wire for the light in the switch and sometimes a grey/red wire for dash lights, the wire to the back window is fatter than the rest and black.

The dome light is constantly supplied with battery power by a red wire from the fuse box, when you open the door or move the switch on the light it grounds the other end of the bulb. Check for power at the red wire and clean all the switch and door switch contacts (brown wires, some with a white stripe).

Mon Nov 02, 2009 12:35 am

Ok, so I checked all my connections with the bentley and it all seems to match up and I still can't get this headlight to work correctly.

Could it be the dimmer relay? I followed the wiring from the headlight to the fusebox and all is in order.

I have to say that I am glad that there isn't much messed with in the electrical system. I should be in good order after I figure out what is goin on with this headlight.

Got the dome lights to work, thanks.

And I'll look it up in the bentley later, but I just need to know where to hook up the fatter black wire going to the rear defroster. At the moment it is lying around.

Mon Nov 02, 2009 6:50 am

ranzuo wrote: I followed the wiring from the headlight to the fusebox and all is in order.

When you say followed, do mean visually, or did you check for voltage? I assume that you are just looking at the wire and connections. This is not the way to troubleshoot electrical problems. You need to check for voltage. Begin at the switch and work your way to the headlight.

Mon Nov 02, 2009 7:07 am

ranzuo wrote: I followed the wiring from the headlight to the fusebox and all is in order..........

From the headlights to the fuse box? or headlights switch to the fuse box? The wire from the headlight switch goes to the relay and the wires from the relay go to the fuse box, then the individual headlight wires go to thier respective lights.

The big black wire for the rear defog goes on the switch below the glove box. The black wire feeding the switch goes to (comes from) the fuse box.

Mon Nov 02, 2009 11:04 pm

Ok, so I just visually checked the wiring for routing and condition. I haven't yet checked voltage. I'm not the best at wiring, but do have a multimeter so I'll give it a shot.

Thanks for the info on the defroster wire.

Mon Nov 02, 2009 11:53 pm

Good to see you are getting lots of great experience. When we're all up there for the August KOA Kampout we'll know who to contact for help if we need it :wink: