2 electrical problems

AndyinCT · January 22, 2020, 06:06:02 PM

Hello!
I need help diagnosing 2 electrical issues.
1) maybe this is normal but its my first MCI - when I shut off the engine the brake lights stay on. I have to throw the master switch on the batts to get them off.

2) when I hook up the 12v house battery, the clearance lights come on. No idea on this one.

Any help or information you could provide to begin to diagnose would be great.
Thanks!

DoubleEagle · January 22, 2020, 06:22:36 PM

The brake lights being on until you hit the disconnect switch happens on my Eagles too. The clearance lights being on while the house battery is on is the result of some miss-wiring. You will have to trace the wires to see where the mistake is. The previous owner is always the culprit.

AndyinCT · January 22, 2020, 06:35:14 PM

Ok, thanks! So the brake light issue is normal. Is there a way to override this so I dont have to switch off the batteries all the time?

As for the clearance lights -
I was afraid you were going to say I had to chase these wires...

Lin · January 22, 2020, 09:32:24 PM

If your release the parking brake do the brake lights stay on? I believe that my brake lights go on when the parking brake is applied. However, they turn off with everything else with the dash main switch.

richard5933 · January 23, 2020, 02:56:53 AM

My GM's brake lights are on any time the parking brake is set AND the "ignition switch" is in the on position. Once I turn the key off, they go off. Perhaps yours are connected to the wrong side of the switch, if you have one.
Parking lights being on i can't explain. Perhaps they are not correctly wired to the headlights switches.

Do you have an "ignition switch" of sorts on the bus that you have to turn on before starting? If so, check to see if it's wired correctly.

AndyinCT · January 23, 2020, 03:52:18 AM

This bus doesn't have a key switch, it has a toggle switch for the ignition and 24v power. The brake lights stay on with the switch "on" or "off". ONLY way to get the brake lights off is to throw the giant Frankenstein battery lever in the cargo area.

richard5933 · January 23, 2020, 03:59:21 AM

Unless this is how all the MCI buses of this model are wired, I'd suspect that the brake lights should turn off with one of those switches. That would be a question better answered by someone familiar with MCI.

If they are the only thing that remains on, then I'd be double checking the wiring diagrams to be sure things are in the correct place.
Assuming that this is the only circuit remaining 'on' with the switch(es) in the 'on' position, it wouldn't be that difficult to add a relay to the circuit to have them turn off with the dash switch.

buswarrior · January 24, 2020, 06:36:14 AM

Something wrong.

Brake lights on with either foot brake or parking brake, when ignition is turned on.

All should be dark with ignition off.

Start formulating profanity aimed towards previous owner(s)...

Electrical fires due to idiots are not uncommon... better get both of these tracked down to see what other crap has been done. Rarely is stupidity confined to a single observable fault...

Too harsh?

Happy coaching!
Buswarrior

Happy coaching!
Buswarrior

AndyinCT · January 29, 2020, 04:07:46 PM

Quote from: buswarrior on January 24, 2020, 06:36:14 AM
Something wrong.

Brake lights on with either foot brake or parking brake, when ignition is turned on.

All should be dark with ignition off.

Start formulating profanity aimed towards previous owner(s)...

Electrical fires due to idiots are not uncommon... better get both of these tracked down to see what other crap has been done. Rarely is stupidity confined to a single observable fault...

Too harsh?

Happy coaching!
Buswarrior

Happy coaching!
Buswarrior

Not too harsh at all! I just don't know where to start with the brake light issue. I guess its an air pressure switch due to the fact that it has air brakes?

richard5933 · January 29, 2020, 04:37:55 PM

Do you have the wiring diagram?
If so, start with the forward electric panel and start tracing the brake light circuit. My hunch would be that someone connected a hot lead to the brake light circuit (relay) from the wrong side of the ignition switch.

buswarrior · January 30, 2020, 08:18:12 AM

I have seen the bus engine start through an 18 gauge jumper wire, that someone installed for powering something else, bypassing the ignition...

Makes some great smoke...

I'm not kidding when i say previous owners burn down their buses, whether during their ownership, or during yours...

Wires that bypass systems have unintended consequences.

Happy coaching!
Buswarrior

AndyinCT · January 30, 2020, 06:41:47 PM

Quote from: richard5933 on January 29, 2020, 04:37:55 PM
Do you have the wiring diagram?
If so, start with the forward electric panel and start tracing the brake light circuit. My hunch would be that someone connected a hot lead to the brake light circuit (relay) from the wrong side of the ignition switch.

I don't have a wiring diagram but this makes sense. Many of the dash panels are loose so I'll look for signs of hacking...

AndyinCT · January 30, 2020, 06:44:20 PM

Quote from: buswarrior on January 30, 2020, 08:18:12 AM
I have seen the bus engine start through an 18 gauge jumper wire, that someone installed for powering something else, bypassing the ignition...

Makes some great smoke...

I'm not kidding when i say previous owners burn down their buses, whether during their ownership, or during yours...

Wires that bypass systems have unintended consequences.

Happy coaching!
Buswarrior

I was just watching a busgreasemonkey video with and MCI and there was a fire below deck from some 110 electrics! When the weather is warmer and the days are longer I'll have to go through it all.
Anyone in the tristate area that can lend an expert eye?