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Battery Isolator

July 24, 2021, 12:11:03 pm

Hello Forum Members,
We are the owner of a 2007 Nimbus with 500 HP Cummins. Woke up a couple nights ago to a bedroom filled with smoke and a loud hissing sound. We scattered out and when it settled down went back to investigate. Battery isolator had arced across all post and either caught fire or was hot enough to ignite surrounding materials. the hissing noise was the Freon escaping from the burnt pressure hose.
  Lots of burnt wires and coverings but I didn't see anything shorted outside the isolator itself. Patched all the wires and have a new Cole-Hersee isolator coming today. Everything seems to be OK but I haven't tried to start it yet (will after I wire the isolator back in).
  But now that I see what it is, I am wondering why? Is this something that was caused by another issue or was it time for this part to fail due to age or ?? I would appreciate any thoughts.
Call us lucky.....

 Larry and Kay
2007 Foretravel Nimbus
2007 LX470 TOWED
Molly the Wonder Dog

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Re: Battery Isolator

Reply #1 – July 24, 2021, 12:31:37 pm

Unusual!

All posts on the diode-based battery isolator (assume that is what you have) are positive.  So, even if they all connected together, it would just act as a kind of battery combiner/boost.

Now, if anything from chassis ground (i.e. any metal) touched any of them, that would be a dead short with no fuse to protect it.  That WOULD heat up very rapidly as you would have one or more battery bank in a dead short condition.

Any evidence of anything that had gone from any chassis metal to any of those isolator posts?

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Re: Battery Isolator

Reply #2 – July 24, 2021, 12:33:38 pm

Glad the incident was not any more serious, although I'm sure it was a major scare.

I don't recall any reports on this Forum of a catastrophic failure like this.  Usually isolator just stops working due to weak or failed diodes.  Result is failure of battery banks to be properly charged from the alternator.

I'm not familiar with the location of the isolator in your coach.  What is the "freon pressure hose" that you mention?

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Re: Battery Isolator

Reply #3 – July 24, 2021, 12:45:31 pm

No evidence of anything touching the post or the isolator itself but I did notice a 16 volt reading on my chassis voltage meter the previous day. Good thought about that all being positive. The unit is mounted to a metal plate that I'm sure is grounded. The air conditioning hoses (freon) that run to the dash air run directly below the isolator with a large bundle of wires.

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Re: Battery Isolator

Reply #4 – July 24, 2021, 12:51:39 pm

See if this gets you to a pic of the burnt isolator....

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Re: Battery Isolator

Reply #5 – July 24, 2021, 01:04:39 pm

Google 相册

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Re: Battery Isolator

Reply #6 – July 25, 2021, 02:20:58 pm

Quote from: LLLCJ7 – July 24, 2021, 01:04:39 pm

Google 相册

Hi Larry,
My name is Robert Stout. I just purchased a 08' Nimbus 342 from MOT a couple of weeks ago. I couldn't open the picture and was wondering if you could tell me where the isolator is located. I had a charging issue on the drive back to Dallas and wanted to check/replace mine. 
Thanks.

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Re: Battery Isolator

Reply #7 – July 25, 2021, 02:41:20 pm

Quote from: LLLCJ7 – July 24, 2021, 01:04:39 pm

Google 相册

You can post a picture here. I don't want to "join" a place I don't use to see a picture.

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Re: Battery Isolator

Reply #8 – July 25, 2021, 03:49:32 pm

Sometimes when you reply, you will not see the option to "Add files by dragging and dropping or selecting them".  To see this option, just hit the PREVIEW button to the right of POST.  It will take you to another screen where you can continue to edit, but also see the image attachment option.  See picture.

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Re: Battery Isolator

Reply #9 – July 25, 2021, 09:18:57 pm

HI all,
Sorry, been out working on the unit. Got the new isolator from Amazon yesterday afternoon. Decided we might sleep better if I waited and put it on this morning. Had already patched the burnt wires and made new cables between the solenoids and the isolator. After the install all seems to be fine. We went ahead and packed up and returned home this morning (we were just an hour from home).
  Robert mine is located pass side forward in the engine compartment just under the foot of our East/West bed. 9" x 4" x 4". Big heat sink with 3 post. I put the old isolator in my band saw this afternoon and you can see where it shorted internally to the surrounding heat sink. No idea why....heat, vibration, age....I did install some new tie down points for the cables to at least minimize the load the terminals carry. I just need to splice my ac hose and cover and re-bundle the new wire and hope its a fix.
  I'll try and post a couple more pictures but I struggle here for some reason. I understand the response, the last thing I would click on is Google with some Chinese symbols after it.
Stay safe.

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Re: Battery Isolator

Reply #10 – July 25, 2021, 09:30:58 pm

I hope you can see these pictures......

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Re: Battery Isolator

Reply #11 – July 25, 2021, 09:33:56 pm

Thanks WS6_Keith for the guidance

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Re: Battery Isolator

Reply #12 – July 25, 2021, 10:02:31 pm

You did good! That isolater is shot.

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Re: Battery Isolator

Reply #13 – July 25, 2021, 10:34:24 pm

Those Isolator photos will go in the Forum archives for sure.  I've never seen a failure like that.  Makes me glad I elected to do away with our isolator entirely.  One less thing to worry about.

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Re: Battery Isolator

Reply #14 – July 26, 2021, 12:29:15 am

You did great.

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Re: Battery Isolator

Reply #15 – July 26, 2021, 06:19:56 am

Larry,

In the 2nd picture you can see the exhaust system that has a heat wrap. Look this area over real good for an exhaust leak that could have melted the insulation on some of your wiring causing the insulation to exposed wire. With the isolator mounted what appears just above the exhaust that heat alone could have melted the insulation of the isolator.

Mike

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