Small (but very scary) electrical fire

JT4SC · February 12, 2015, 04:45:57 PM

Looks like I need to get a pro out to look at my coach and see whats going on with the electrical wiring.... Any suggestions for someone good in San Diego? Anyone want to come out for vacation, I got a great place to stay!!...

eagle19952 · February 12, 2015, 05:09:30 PM

i am always leery of electrical connections that are covered with heat shrink at terminations ... they can cover a multitude of sins and are not necessary...

in the middle of a wire/splice....ok.

i think the magority of your current problem is mounting, vibration fatigue, and suspect teminations, not wire size, ( would need to see/know) more.

you can buy all the proper pieces and tools cheaper than an expert

luvrbus · February 12, 2015, 05:52:04 PM

That setup should have at least continuous 200 amp relay or solenoid which ever you want to call it, with a intermittent solenoid they will burn the terminals off that is small wire most have a cable ? do you still have the 270 amp alternator

lol I don't know the proper name Del City calls it a solenoid and Texas Industrial Electric calls it a relay same brand,parts number and amps your choice I guess

Lin · February 12, 2015, 06:22:04 PM

A solenoid is a magnetically activated device. It can be a switch or a valve, or something else. A relay is a switching device that is activated by one power source to complete another circuit. Generally, there is a low current source that triggers the relay to complete the circuit on a higher current. An example is your ignition; a low current wire runs all the way back from the dash to your starter motor's solenoid activated relay that connects the cables with the high current needed to spin it. Not all solenoids are relays and not all relays are solenoid activated. The relay you have in your picture is solenoid activated and is almost universally referred to as a solenoid.

If you are going to be trying to trace out wires, you may want to look into getting a tone generator. That tool has two pieces; one that sends a signal through the wire, and the other plays the signal as a tone when touched to the wire down the line. This takes the guess work out of tracing wires. You can determine correct wire size by determining the amperage it is supposed to carry and the length. Wire size charts are available online.

JT4SC · February 12, 2015, 07:25:15 PM

I thought it would be a good idea to take a picture of where I believe the wire Mike connected is located on the main electrical 'board' (on side of coach just below drivers-side window). In the picture I am pointing at the connection. This is the wire which ultimately connects to the right hand side of the relay (which still is good).

This wire is located on the right hand side of the main electrical board, in the middle. It's exact terminal is 3R. Does this change anything?

azdieselman · February 12, 2015, 07:55:09 PM

I know it's semantics, To me, that's a relay. A solenoid uses magnetic force to do work. Like a starter solenoid pulls in the lever to engage the drive gear. Or like an engine shutdown solenoid pulls in the rod to move the fuel rack.

digesterman · February 13, 2015, 02:54:22 AM

The problem could be something as simple as that connection on the end of the wire getting lose over time and getting hot and then burning, happens all the time, lose wiring connections will create a lot of heat because the connection is being maintained through the equivalent of a small wire vs what you see and think you have.

krcevs · February 13, 2015, 04:40:29 AM

I agree with digesterman. If it was an electrical short the wire would have been burned most of its length. A loose crimp will only burn at the crimp.
You need to clean up the mounting and correct how the wires are attached. It looks like the black wire off the solenoid is rubbing as well. HTH
Ken

luvrbus · February 13, 2015, 05:31:19 AM

The problem he has with the set up if he leaves the bridge on when starting, if the cranking batteries are low it will try and draw power through that wire and burn the terminal off Mike never spent money to do anything right after Tom left

eagle19952 · February 13, 2015, 07:40:34 AM

Quote from: azdieselman on February 12, 2015, 07:55:09 PM
I know it's semantics, To me, that's a relay. A solenoid uses magnetic force to do work. Like a starter solenoid pulls in the lever to engage the drive gear. Or like an engine shutdown solenoid pulls in the rod to move the fuel rack.

a relay does not have a movable core, Power relays are called CONTACTORS; control relays are usually known simply as relays.

scanzel · February 13, 2015, 07:50:30 AM

If you look at the red wire and how it is burned for a few inches and look at the crimp connector angled toward the metal wall it looks to me that the vibration finally rubbed through the side of the red wire and shorted it out causing it burn because of some high amperage. Remove the connector and replace the red wire and reconnect it and make sure the crimp end in down and not angled toward the wall. This is just my observation on what I see.

JT4SC · February 13, 2015, 09:55:14 AM

Thanks guys! So if I take what you all have said it looks like the red wire was used to give the starter batteries some back-up from the house batteries. The amount of amperage the house batteries were capable of producing makes the red wire (most likely) too small for that application. The red wire most likely rubbed or vibrated on the wall where the relay is located to create the fire.

I still don't know what the wire Mike installed from the main electrical board to the relay/ solenoid does, or what the middle wire to the black box in the battery compartment does. I do know I need to rotate the relay to make sure no wires are contacting the wall of the battery compartment.

I also need to figure out how the house batteries and generator are connected, and if the red dial pictured in my initial post is correctly installed. I took the red dial off the wall and took a picture of the connections, which includes the other end of the infamous fried red wire (attached to this post).

Jim Eh. · February 13, 2015, 11:35:08 AM

Quote from: scanzel on February 13, 2015, 07:50:30 AM
If you look at the red wire and how it is burned for a few inches and look at the crimp connector angled toward the metal wall it looks to me that the vibration finally rubbed through the side of the red wire and shorted it out causing it burn because of some high amperage. Remove the connector and replace the red wire and reconnect it and make sure the crimp end in down and not angled toward the wall. This is just my observation on what I see.

^ Gets my vote. Turning the relay will create strain on other wires because the terminals are positioned all around a the cylinder. The last picture you posted looks like the small(er) gauge red wire was pinched under the switch when mounted. Another future issue?

TomC · February 13, 2015, 12:48:20 PM

I have the same set up on my bus to charge the house batteries when going down the road, and to be able to jump start the starting batteries if need be. Since my bus is 12v, the DN50 alternator is 300amp. I bought two continuous rated 150amp relays and used heavy gauge steel to strap them together to make their capacity 300amp. Even if the alternator is pumping out the full 300amps (which is rare), the relays will take the load. My cables are also 3/0 to handle the 300amp load.
I have also used the relays to jump from the house batteries when the starting batteries were to low to start the big engine. Very convenient to have! Good Luck, TomC

gumpy · February 13, 2015, 02:38:39 PM

That solenoid is there to charge up your house batteries from the bus starting batteries, not the other way around. The other side of the solenoid is connected to the 12v terminal
of the Vanner, so I assume you have a 12v house bank. I also assume there are no fuses on either end of that red wire?

Now you know why they make fuses. If one had been installed, it would have blown. On a system of this nature, you should have a fuse on the house side, and one on the black
wire between the Vanner and the solenoid. However, the Vanner has a circuit breaker, so you're probably ok on that side.

That terminal broke, probably due to fatigue, and the wire shorted to something. It didn't short to the panel the solenoid is mounted on because that's fiberglass, which
isn't conductive. It may have shorted to the solenoid itself. There's probably a negative ground wire attached to it for the solenoid coil. It may have grounded to the metal
frame that main disconnect is attached to, though it appears to be mounted to the fiberglass, too.

There's no concern of the bus starter drawing too much current through that wire because the Vanner is in between. And you don't need bigger wires because the Vanner is limited to 35 amps or so. But you do need a fuse on the line.

It's poor workmanship. You got lucky. But it may not be over.

What I'm about to say may sound harsh and over critical, so please know it's meant with the best intentions...

I'm concerned that you've owned this bus for 7 years and don't even know how your electrical system works. Makes me wonder what else has been neglected. Are you having the coach
maintained professionally? Are you watering the batteries? Adjusting brakes properly? etc. The electrical system is a basic system and you need to have an understanding of how it's
put together, what all the components do and how they work. You don't have to be an expert, but you need a good working knowledge of it. This is a prime example why. You didn't indicate what you did, so I'm guessing you didn't turn off the house batteries, and therefore are holding a hot wire in the later photos? Do you have a disconnect on your house batteries? Does it
disconnect power to that wire, or does it run directly to the battery terminal?

Yes. You need to get an electrician out to look at this system and explain how it works. Have him install a fuse.