bad foot dimmer headlight switch

[Tedsoldbus]

I really am trying to get better at fixing this bus myself. I'm about to go to Indiana for a new fridge, and my headlights said "thanks for playing!".
I don't drive at night but pretty stupid to leave home without lights. I'm getting good at multimeter and spent 2 days determined to figure it out. Out of time, I did the 2 hour drive of shame over to my Prevost mechanic. We call it camp Benjamin because you better bring some Benjamins if going there. I felt somewhat better when his pinball wizard who figures out all things electrical - took 2 1/2 hours to figure it out instead of his usual 10 minutes. Headlight switch checked out, all wires to relay were still on the mark. All wires into the headlights were good. ( I checked all that but watched in quiet fascination as went through his steps. He NEVER fails.)
This old bus still has that beloved foot switch to change from bright to dim. Until we got this bus, I had not seen one since the trucks and Camaro cars of my youth! I love that the bus still has one!
I had checked the wires going in and out of the footswitch. They tested good. Pinball wizard saw the same thing, but then he stared at the switch with distain and a squint in his eyes for about 3 minutes. He doesn't say much, and I've learned I shouldn't attempt to talk to him when he stares at something...
He went away for a while. Came back with screw gun, tools etc and removed the panel under wheel well and pulled out the dimmer footswitch. Well protected, it was not rusted. Just old. The footswitch was bad but the wires did not tell us that. So an hour later I got some brandy new wires, a new foot switch (NAPA still has them!) and a few Benjamins later, I'm back home.
I know, I know. The old guys are laughing right now. Rita says I am slow but trainable, but I am not giving up. What bothers me is that when I fail and they fix something like that, my 2 days of diagnosis should have worked? And though the repair was interesting to watch, I'll never need to change that again!
So the teaching points are: I have lights. A brand new really cool dimmer switch. People that do this all the time know more than me. I have less money in my wallet. Guess that is about it....
Though I never expect to have to fiddle with that switch again, I share this to give the mechanics a chuckle and hope it helps somebody else when your lights say "Not today Skippy".
My next smart move is to head north on Friday for a Sunday appointment at Shipshewana. That should pretty much have me in the ugly storm crossing the country from the time I leave until I get there. You know what Forrest Gump's mamma says about stupid....

[dtcerrato]

Shipshewanna is the best place in the country to be bringing an RV fridge!
We have three dimmer foot switches, one for the low - high beam headlights, one for the low - high beam fog lights, & one for the 1953 NYFD 6V fire engine hood alarm - yep - just added that as it was in the shop junk box for decades. I just hope I'm never stupid enough to be cited for using it at the wrong time because it is LOUD.

[windtrader]

Appreciate posting your experience on chasing electrical issues, never enough ideas to spin through why something is not receiving correct power.


In general,  how does one know if a circuit is corroded or rusty? For example, in this headlight instance, it seems the multimeter shows adequate voltage on the circuit. A semi-failing switch in this case but could be any corroded piece of wire or connection that probably can't pass the needed current creating the fault.


Is the way to diagnose different if the suspected source is on the positive or negative side? Most situations posted here end up at the ground wire. Again, there could show voltage but can't pass the current. Is there a simple current test? It seems if you have to put the rated load onto the line, you need testing equipment that most DIYers don't have in the box.

[Tedsoldbus]

Thanks for making me feel a bit better. I have learned over the years I should not mess with any kind of natural gas, electricity, or the big spring above the garage door. I have decided I MUST learn to play with some electricity if I plan to own a bus. At least my Prevost is "pre" all the lighted mirrors in the ceiling, Liberache guchi lights everywhere, and it still has just one TV and no fireplace that pops up out of the floor. However, can't be going to camp Benjamin every time there is a light bulb flickering. I'm learnin'

[Jim Blackwood]

Many VOMs have a 10 amp circuit for measuring current up to that level. But headlamps provide enough of a load to be able to measure a voltage drop across a bad switch. Therefore with the headlights on, a bad connection or switch should show a voltage when measuring across it. A perfect connection would show no voltage.

Jim

[chessie4905]

mine was bad when we brought ours home. had to hit button 3 or 4 times to get them to stay on. easy to replace. wires to switch in drivers compartment.

[belfert]

In general,  how does one know if a circuit is corroded or rusty? For example, in this headlight instance, it seems the multimeter shows adequate voltage on the circuit. A semi-failing switch in this case but could be any corroded piece of wire or connection that probably can't pass the needed current creating the fault.

A little story related to this, but with a riding mower instead of a bus.  My neighbor called me on Sunday because the electric clutch on his riding mower didn't work.  I checked at the plug at the clutch and I swear it was showing over 16 volts with the engine running and the PTO turned on.  I turned the engine off and ran wires straight to the plug from the battery.  The clutch clicked on as expected.  I was stumped at that point and my neighbor was just going to wire the clutch straight to the battery with a switch.

My neighbor happened to show me the plug at the ignition switch.  The plug was melted pretty bad, but everything was still connected.  I replace the plug with crimp terminals and the deck switch worked fine after that.  Only 14.xx volts at the clutch too.  I don't know if the melted wires were not letting enough amps through or what?

[belfert]

The only problem with my high beams is the high beam indicator light only glows faintly when the high beams are on.  I suspect I may have a 12 volt light bulb in a 24 volt socket.  My dash lights are a combination of 12 volt and 24 volt.  The exterior lights are all 12 volt.  It hasn't bothered me enough yet to open up the dash to check.

[Tedsoldbus]

My switch was easy to get to as well. I tested the wires but not smart enough to know it was the footswitch. Glad it was not the dash switch. I pulled that part way out hoping for a loose wire. They were fine. All 9 of them! 

[Jim Blackwood]

That dim high beam light is more likely a 24v bulb in a 12v circuit.

You can think of an electrical circuit kinda like a water hose. You cut down the flow (resistance) and the pressure builds up. (voltage)

Jim

[buswarrior]

Lots of people would love to have a dim high beam indicator...!

Be careful what you wish for!

Happy coaching!
Buswarrior

[belfert]

That dim high beam light is more likely a 24v bulb in a 12v circuit.

Oops.  I meant a 24 volt bulb in a 12 volt socket.  A 12 volt bulb would likely die immediately from the high voltage.

[chessie4905]

If you have a too bright high beam indicator, just add a resistor or rheostat to the wire going to the bulb. You could also go to a lower candlepower bulb.