ELECTRONIC MELTDOWN

SunMan

SunMan

King Taco
Joined
Sep 9, 2007
Messages
2,364
Location
Oxnard, CA.
This is a bit long so please bear with me here.

We were heading home yesterday from the Racetrack via Lippincott after 4 epic days in Death Valley, approaching Lee Flat on Saline Valley Road (heading downhill) I tap the brakes to slow down and the pedal hits the floor, I pump it several times as we are picking up speed and quickly go for the E brake and stop the rig uneventfully as I see blue smoke pouring from under my hood. WTF?

I get out and pop the hood and watch the hotwire that goes from my battery to the isolator and back to the blue top house battery in my camper literally melting down. I run back to the camper and let my poor dog out of the now smoke filled camper, pull up the couch and detach the hotwire from the house battery as it is melting down. I continue to see smoke coming out from the front of the camper so I unload the better part of my fire extinguisher on it, let the smoke clear and try to assess the situation.

While following the burnt wire going into the bed of my truck and camper I noticed a burnt spot that looked almost arc welded as if perhaps the insulation of the wire rubbed through and caused a short. This is my theory as to what caused this event.

Ultimately after cutting all of the connections my truck started fine and my brakes functioned properly and we drove home uneventfully.

Some questions I have for you electrical gurus:

- Does my above theory make sense? Was this just a simple short?

- Would an event such as this have fried my isolator or would the current have just passed through without harming it? How can I test the isolator to be certain? I have a fluke multimeter and know just enough to be dangerous with it.

- Is there anything else I should be checking? Electrical components in the camper?

- Why the hell would my brakes have gone out and now be functioning fine?

If my theory is correct I'm hoping I can just replace all of the wires and be good to go but I'd hate to wire it all up only to fry it again. Comments, opinions and theories welcomed and if I need to take it to a professional I will.

Anyway, just thought I'd share my story and see if I can't learn a little something as well. Ultimately I'm just glad we made it home safely and that this didn't happen 40 minutes sooner on Lippencott, I shudder to think what could have happened.
 
EEEEKKK !

:eek:


Did you have any in-line fuses ? ?

Did you have a thermal breaker somewhere in-line ? ? ?

What kind of isolator were you using ?


The main camper wiring could have rubbed down somewhere under the truck and starting touching the frame ?

The only time I have heard of something severe like this, is if the customer did their owner camper wiring, did not use any in-lines fuses or a thermal breaker, and hooked up the camper wiring opposite of what it should have been.


Electrical can be very strange.

When things go crazy, sometimes the camper works great and only a few items won't be working.

Other times the entire system can melt down.

:(


But the truck brakes ?

Not sure on those ??

Maybe the short / current was running through the truck frame and freaked out some sort of electronic brake sensor ?



.


.
 
Sounds like a direct short to a solid ground. I've seen large'ish wires melt like that before. It was sucking the truck battery to the short and the camper battery to the short. I'm guessing no fuses/breakers anywhere in lines? I have a 30 amp self resetting breaker in my to the camper line from the truck - I hope it would prevent a situation like this.


I'd check everything - but unless the HUGE amps were going through the device it should all be fine. But the back feeding through the ground of that many amps - could have screwed stuff up - I'm guessing that is what happened to the brakes - the computer/sensors for the brakes went crazy when power started coming up the ground side of the system and it threw the resistance or whatever readings it uses way off. If you weren't freaking out from the smoke - I bet you would have seen your gauges/speedometer/lights/etc were going nuts as well.

I had a short in a truck on the cable from the battery to the starter - it drained my battery and melted the wire in seconds... Scary stuff.
 
I think you maybe lucky and only have a bad feed to the camper. On the rewire I would put a thermal breaker no further than 12" from the battery to the camper.
 
To answer some of your questions, I had the isolator and wiring installed at a local RV company, thinking about the set up now I don't think there is a fuse/thermal breaker in there that I can think of (note to self). The set up has been fucntioning fine for over 3 years.

I'm not sure what brand the isolator is and am having trouble finding an image of it online at the moment. I think I agree with Stan and Uglyscout that is was just the current making things go haywire temporarily, its good to see others think that is a possibility too as that was my original thought.

Realizing anything is possible and certainly holding everyone harmless is the consensus that it should be reasonably safe to just try a re-wire?

You can be sure I was freaking out. All I can truly remember seeing on the instrument panel was that the ABS light was lit or flashing but obviously i was concentrating on getting us stopped quickly!

I really appreciate the rapid input and if there is anything else that comes to mind please give me a shout here or via PM. Camper comes off tonight to inspect for any other damage.
 
Whoa, what a story! Glad you are okay. I also have a 30 amp fuse under the hood on the line going back to the camper & house battery. Sure hope it would blow if the same scenario would occur. Hope the simple cause is it and no other damage has happened and its an easy fix for you.
 
Likely just the short. Most likely no other damage but I couldn't rule any out.

Aren't drive by wire vehicles fun? In the old days you'd never have lost your brakes.
 
That's a bad place to loose brakes, I'm glad you managed to stop your truck and extinguish the immediate problem!

A high current short circuit or an open ground can find all kinds of weird paths through with to complete the circuit. I'm not familier with your truck, but I assume that you have either Rear Wheel Anti-lock Brakes (RWAL) or full ABS, nor do I know how your camper battery is grounded.

Assuming that the camper battery is grounded through the bed of your truck:
1) It's possible that the current from the short of your camper battery was more than truck bed's ground could handle.
2) Therefore, the battery returned current through the path of least resistance, which may have included the ground for your Brake Controller Module (BCM), and other components.
3) Hopefully there was no permanent damage (other than the burnt out wires you already found), but I would inspect all of the wiring aft of the bed, especially the wires leading to the rear brakes.
 
To answer some of your questions, I had the isolator and wiring installed at a local RV company, thinking about the set up now I don't think there is a fuse/thermal breaker in there that I can think of (note to self). The set up has been fucntioning fine for over 3 years.


Wow that is pretty hacky of them honestly.


I'm curious of the spot you saw the arc welding, was there a ruff spot for the wire to have rubbed through on? As for the rewiring I'd say wire it back up (WITH FUSES OR BREAKERS!) and check things out.


I was bombing around a 2 track in a beater truck in my youth and flipped the battery over on a bump, it liquefied some wires quite rapidly. :eek:
 
what happens alot of times is that the charge wire from the truck is fused or has a breaker close to the truck battery, but the camper battery does not, so if the wire shorts out or rubs on the frame and shorts out it will melt the wire back to the battery in the camper or the weakes spot, power flows both directions thru charge wire
 
what happens alot of times is that the charge wire from the truck is fused or has a breaker close to the truck battery, but the camper battery does not, so if the wire shorts out or rubs on the frame and shorts out it will melt the wire back to the battery in the camper or the weakes spot, power flows both directions thru charge wire


You know that never occurred to me, that is a really good tip. I'm betting a bunch of rights are set up properly for this kind of protection. Thanks!
 
Glad you're safe, Sunman,

The first thing I would do, before hooking the house battery back up, is to get a diagnostic report from a Toyota dealer to find out why your brakes did not work. I am SWAG-ing that a pulse caused your ABS system to fail.

The second thing I would do is take pictures of everything along with copious notes and visit with a lawyer. No kidding.

If in fact you paid to have this dubious set up, a letter from an attorney might help you get some of the repair costs covered. Moreover, you might help prevent an even worse future accident for yourself or some other innocent victim. I am not talking about suing here, I am just talking about getting things put right.

Back to your your general question about what went wrong, when circuits fail they do counterintuitive things. That is why the National Electric Code (NEC) is so counterintuitive in some places.

Perhaps the isolator failed. Perhaps you developed a short where you suspect you did. In any event, I believe you should have had at least one fusible link between each battery and the next potential short circuit, just like circuit breakers in your house wiring.

I have a fuse to the ground wire of my house battery, too, and I don't understand why that is there, now that I think about it. I just accepted it uncritically, since it was always present, but I will ask around and see what my power conditioning colleagues think of this practice.

The limited wiring I have seen in RV's is egregious and violates the principles of common sense, not to mention the NEC, for example splices buried inside walls and ceilings where they cannot be inspected or repaired. Apparently, the RV manufacturers do not have to comply with the same standards that homebuilders do. Too bad.

I was fixin' to redo the wiring in my 2000 Hawk, and now I *know* I will before the next meander.

Mark W. Ingalls, MSEE
 
Thanks everyone for your thoughtful input. I was hoping sharing this mess might help someone else down the line as well as help me learn a little more about the electrical system. Hopefully more than a person or two has checked their systems. I intend to repair this myself so that I understand the mechanics of the system instead of relying on someone to do a shoddy job and not realize it. Also it will help during any future trouble shooting if something happens in the field. Glad I at least knew enough to terminate the circuit before things got worse.

As to where I saw the arc weld spot there was a plastic plug in the bed where the wire was routed but it may have been damaged, not really sure. The camper is off and I took a really good look at all the truck wiring in the engine compartment, other than a few singed wires eveything looks good, no penetration on the insulation. Same goes for the rear end and brake system. The ground was attached to the bed but the hot wire was fried from battery to battery, probably 10-12 feet of wire. Hopefully I'll get out of the mess for the cost of a new AGM battery, fuses/breakers and some wire. Fingers are crossed. This site is the best, there are some real smart folks here. Many thanks.
 
Jiminy, I was trying to forget the partially-melted wire running from my camper battery to main distribution panel but I think I'll be sure to fix that before the next trip, which I believe is this weekend! Yikes!
 
Wow, quite a story is right. Glad you had a 'mechanical' or should I say 'electrical' on the flat side of things. Funny, that's not far from where we met you and where I had my DV breakdown (well, one of three I've had there).

Hours of driving washboard and rough road does stress all the systems, but this sounds quite dramatic. Good job keeping a cool head, saving the truck, and occupants including the dog from a variety of catastrophic possibilities.

I'm no electrical expert, but I've arced a wrench against a battery a few times and seen the power of direct current with serious amperage. It ain't pretty when it goes direct short.
Your approach of learning the why's and how to's will payoff on some other out-of-the-way place in the future. Good luck with the rewire!

Andy
 
I am not a fan of grounding a high current system to the bed of a truck. The truck bed might only be bonded to the chassis via a smallish size braid (as on my 2005 Dodge RAM 2500), the bed bolts could be rubber isolated from the chassis or on paint and making poor electrical contact.

For the marine industry standards, a fuse or breaker is required within something like 6 or 7 inches of a power source such as a battery to protect the wire melting down in case of a short downstream.

I have a 2006 Grandby I acquired a month ago. There was a nice blue top (marine) Optima battery with what looked like 2 factory installed sheathed 10GA wire pairs connected with no fuse or breaker anywhere near the battery. This really bothered me and so just 2 days ago I installed a 40amp self resetting (Type 1) automotive breaker in the main power cable, and a 10A ATC fuse in an automotive inline 12GA fuse holder, also very near the battery.

From the truck side I use a 60amp self resetting automotive breaker 4" from the battery feeding #6 cable run under the chassis, in split loom for abrasion and weather protection, run up under my driver seat to a Blue Sea Systems ACR7600 automatic charging relay. I have a manual overide switch to power on (or off) the load side which can be used to boost the starting battery if needed.

The output of the relay feeds my ham radio gear located under the other seat, and also continues directly to the DC connector in the bed of my truck for the camper power (also via #6 marine grade tinned copper and short bit of #8 for low voltage drop at high currents my radio gear can create). This way the radio gear gets power primarily from the camper battery and does not wear down my starting battery when the engine is off, and the solar system on the camper helps slow down the camper battery discharge some.

When ever the engine is running everything is tied together automatically unless I flip a switch. When the camper is off the truck I switch the relay always-on since it measures voltage on the load side and won't autmatically close of there is too low a voltage (possible fault condition - like a short).

One cool feature of the ACR7600 is that the load side is current limited to 60amps, 150A for a few seconds for an emergency start/boost, then tapers down the limit. This allows you to run smaller wire than the battery side connection with no extra fuses until the battery fuse/breaker.

I prefer the use marine grade DC power wire since it is tinned copper with very fine wire strands which tolerates flexing and corrosion better, and the jackets are rated for higher temp and oil and water environments. I have seen to many instances of standard solid or stranded copper house wiring used. That stuff does not like flex and vibration. I found it used as battery wiring to a 120HP outboard engine once. The crimped terminals under the cowling were all loose and half the strands were broken. Scary.

Since I need power in the cab of the truck from my camper battery, I bypassed the in-camper automatic relay that was standard.

- Mike
 
I am not a fan of grounding a high current system to the bed of a truck.


From the truck side I use a 60amp self resetting automotive breaker 4" from the battery feeding #6 cable run under the chassis, in split loom for abrasion and weather protection,

I prefer the use marine grade DC power wire since it is tinned copper with very fine wire strands which tolerates flexing and corrosion better, - Mike


All good points, noted. I used split loom to protect my airbag lines, why would I not use it for its correct intent?
 
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