95 Crown Royal close call with electrical fire... need help

[153stars]

Yeah that isolator looks toasted as well and going to need new cables made up . That's why I casually suggested Bluesea magnetic latching ACR as well as another poster.Two "birds" one stone.You're looking at $150 on low side for the pair already. I haven't ran down every spare wire in my crown royale for the control switch but there's a whole loom of wires front center of dash , behind Magellan GPS and security system unit. I would make real close inspections of all cables, then take pics ,strip out all burnt stuff, take some readings for shorts and maybe make up 10 gauge test jumper/s with a fuse/s to double check" not jump batteries or anything high power." There's still a mystery of what happened in my mind "root cause". Maybe just the boost solenoid went all catastrophic and shorted to ground just sitting there ????.

[CrownRoyale]

I have not had time to tear into it yet. But I think the solenoid was stuck on for quite a while, that's why batteries are running down & eventually it burnt and went to ground. Was planning a trip on the Christmas break but that's probably not going to happen now.

[YC1]

If that big cable was indeed glowing you have a massive short and you must find the cause before throwing parts at it.

It is possible they reverse charged a bank of batteries. I'm trying to think out of the box here. Why didn't it go up in smoke on the way home?? Not sure of course.

More pictures would sure help. I have worked on vehicles for close to 50 years installing telecommunications equipment and public safety gear of all kinds.

A couple of voltage readings would be important to start. Both battery banks of course.

I know they are disconnected but need to see if your house bank is reversed or shorted.

Then I would start at the burned area and follow that heavy cable. It could be pinched somewhere. Again out of the box thinking. Suppose it got caught under some radiator mount and the insulation wore through on the way home. Whatever the cause it may or may not be from the service shop but document every area closely with video and stills.

At first glance it looks like the combining solenoid is directly below the isolator.

The combining solenoid is very unlikely to cause such a short. If it did I suspect from the massive current it would about crumble in your hand. Again, more close ups.

[doublechevy]

with that kind of damage and not knowing your coach wiring Schematic
I would be wondering why the protective battery fusing did not limit the damage or even prevent it

I have seen this kind of burning of cables and connections due to loose connections and a high current demand

this damage appears to be excessive especially when not having any previous indications or problems

[153stars]

I was suggesting a fused jumper after testing for a short . The battery isolator or the combiner really don't need to be there to use the coach. Could just bolt alt. to chassis cables instead of on isolator. Then test to combine around the combine solenoid with both sets of batteries fully charged for limited draw. Will still need some cable repairs. I supposed it could started arching inside of solenoid burning off copper creating a plasma arc. The fuses may have been too high to trip or none used there, they do combine to start rig.

Originally Posted by YC1

If that big cable was indeed glowing you have a massive short and you must find the cause before throwing parts at it.

It is possible they reverse charged a bank of batteries. I'm trying to think out of the box here. Why didn't it go up in smoke on the way home?? Not sure of course.

More pictures would sure help. I have worked on vehicles for close to 50 years installing telecommunications equipment and public safety gear of all kinds.

A couple of voltage readings would be important to start. Both battery banks of course.

I know they are disconnected but need to see if your house bank is reversed or shorted.

Then I would start at the burned area and follow that heavy cable. It could be pinched somewhere. Again out of the box thinking. Suppose it got caught under some radiator mount and the insulation wore through on the way home. Whatever the cause it may or may not be from the service shop but document every area closely with video and stills.

At first glance it looks like the combining solenoid is directly below the isolator.

The combining solenoid is very unlikely to cause such a short. If it did I suspect from the massive current it would about crumble in your hand. Again, more close ups.

[twinboat]

You know that you can weld with 50 amps.

A bad connection on a 12 volt system, with large cables, arcs and creates large amounts of heat.

I have sent the type of damage the OP has many times. It wasn't a short or reverse polarity, just a bad connection at the cable end.

Even if the cables were fused, most starter cables are not, including boost start circuits, resistance in the circuit limits the amp draw and wouldn't climb high enough to blow fuses rated for that cable size..

[gofastnow]

Might venture to say (guess) that it was a simple breakdown of the cable post insulator with resulting battery + taken to ground thru the steel housing of the solenoid, but I would follow previous suggestions to thoroughly ohm out all connections prior to replacing the solenoid.
Something owners of older Monacos, and my guess other coaches, might also want to be aware of is with the design of the OEM alternator's positive cable post NOT being of press-in design, the post to rectifier plate connection can become lose over time. And this can result in high resistance between the battery post and the rectifier plate internal to the alt possibly resulting in a meltdown of the rectifier plate. I experienced this. As happened, my voltmeter indicated no charging was occurring and upon immediate inspection I discovered smoke rising from the alternator. Took alt apart and it was toast inside, fire wasn't far away. New replacement alt had modern press-in design post, so I used a nut on nut fastening of my battery cable to the post and confident of a less troublesome connection. Especially for older coaches, I might suggest a tightness check of your alt's battery post / cable connection. If I had checked mine I believe I would still be running with the original alternator.

[CrownRoyale]

I am finally ready to start fixing my coach it has been setting since December and I just have not had time to work on it. I think I have found the isolator and battery parallel relay on Amazon and the cables I can source from my local parts store.

[CrownRoyale]

https://www.amazon.com/dp/B001VIXLRO...ing=UTF8&psc=1

Or yes I can go this route I suppose.
However I'm not sure how it needs to be hooked up in place of the isolator and the solenoid

[YC1]

If you don't have confidence in a re-design, put it back as it was and you will get many more miles out of it along with many others with the same setup.

Why "install" more problems if you do not or cannot do it with confidence.

It worked the old way just fine for a long time. Loose connection most likely contributed to its demise.

[153stars]

Search here Bluesea there are pics and drawings in one post. Forget the big solenoid all together this will take place of both. Put this where isolator is. Put ALT wire to chassis on one lug. The house to other. You have 1 wire from dash and ground already that was combiner solenoid for the red switch. Anyway look for a bundle/loom of a dozen or so spare wires on drivers side motor under bed on top of frame rail. I'm pretty sure the other end of spare loom under center of dash console door . Check colors at each end. Test for voltage each end and if grounded to be safe. Pick a couple tie them together say yellow and blue if tied they go to zero ohms you identified them chose another color use yellow or blue again to say a red . Use these spares for red switch. Or buy a multi wire cable and run new.

[nvs4602]

Sounds like you should file an insurance claim, and let a professional fix it. You be further ahead and if something happens you can go back on them.

[gofastnow]

Originally Posted by 153stars

Search here Bluesea there are pics and drawings in one post. Forget the big solenoid all together this will take place of both. Put this where isolator is. Put ALT wire to chassis on one lug. The house to other. You have 1 wire from dash and ground already that was combiner solenoid for the red switch. Anyway look for a bundle/loom of a dozen or so spare wires on drivers side motor under bed on top of frame rail. I'm pretty sure the other end of spare loom under center of dash console door . Check colors at each end. Test for voltage each end and if grounded to be safe. Pick a couple tie them together say yellow and blue if tied they go to zero ohms you identified them chose another color use yellow or blue again to say a red . Use these spares for red switch. Or buy a multi wire cable and run new.

I replaced the big solenoid and isolator with the blusea some 4 yrs ago on my '94 Crown Royale and have been very happy since with its operation. Found the spare wires as described by 153stars above. As a note, the reason I replaced my big solenoid was it no longer worked due to high resistance (open circuit), across its terminals when energized. Theoretically, that could have caused your failure if yours was energized at time of failure and a high current draw was being demanded, as high resistance equals heat production when current flows.

[CrownRoyale]

I ordered the blusea. Will get it installed next week.