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Topic: Battery isolator (Read 991 times) previous topic - next topic

Battery isolator

While son working on making the park brake set & hold, he noticed a wire not connected to the isolator. It looks to be the red wire from the alternator and it's coming thru a wire loom with a battery connector size wire that  is connected to  that  center post on the isolator. I've not seen a big cable like that connected to the center post before? Gonna go out with a meter in a few to see if that small wire IS the one(same color/diameter) connected to the alternator. I have not fooled with any  of this wiring since I've owned the coach(more than a year). It stays hooked to shore power when not being driven so I guess that's why I haven't noticed low batteries. The Trik L Start has only been installed a few weeks...

Could there be a reason why PO disconnected the alternator form the isolator? I also want to know where the big cable to that center post comes from...

Jim
1992 ORED, 36', White w/Stripe decal(getting old)
Cummings 8'3 Mechanical, 182561kmi. 3299hrs.
Build #4062

Re: Battery isolator

Reply #1 –
The center post on most isolators is the incoming power from the alternator.  Be sure youndisconnect the negative cables from  the batteries (start and house) before connecting anything up again. 

If it is indeed the cable from the alternator you are lucky it didn't short to ground.  All sorts of reasons it might be disconnected.  Is the nut still on the center post?  It might have just come loose.  Maybe a bad alternator or isolator or some other issue downstream.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Battery isolator

Reply #2 –
The nut that's there is holding that humongus cable. there is maybe an 1/8th" of threads that might hold the red wire from the alternator on but I checked the wire  and there is no voltage there with the alternator turning. Gonna look at other connections on alternator to see if it has all the inputs IT needs. I FINALLY made contact with the PO and he said he did not disconnect it and he had the alternator replaced about a year & half ago... Will post more as I learn. Son just drove the coach off to Cookeville. Gonna stop by Auto Zone to ask them to double check Alternator output. May be a first for them?

Jim
1992 ORED, 36', White w/Stripe decal(getting old)
Cummings 8'3 Mechanical, 182561kmi. 3299hrs.
Build #4062

Re: Battery isolator

Reply #3 –
With a "replaced" alternator, first thing is to verify exactly what kind of alternator it is/what connections it has.

It will have a B+
It may have a separate ground-- separate from grounding through its metal to metal connection to the engine.
It may have a sense terminal-- if so, it will be a small-gauge wire from the chassis battery side of the battery isolator.
It may have an "ignition hot" terminal-- if so, it will need to be connected to a 12 VDC source that is hot when the ignition is on.

Let us know exactly what alternator wiring you have and we can help with how to wire it properly!
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Battery isolator

Reply #4 –
Isolator connections should look something like this:

What year and model of coach do you have?
Dan - Full timing since 2009
2003 U320 40' Tag 2 slide

Re: Battery isolator

Reply #5 –
Jim,

If you want to understand the wiring of the alternator and the isolator, and how they relate to each other, you may find the thread linked below helpful.  Mis-wired alternators are common with our coaches because "mechanics" don't understand our electric system.  Once you understand the right way to hook things up, then you will be better equipped to trouble shoot your coach.

What is DUVAC?
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Battery isolator

Reply #6 –
All my sig info got lost when I had to re-register. I attempted to re-do it but it asked me for my old password and the scratch paper I had it written on is gone. I'll keep scratchin' and maybe it'll pop back into my head...
My coach is a 1992 ORED, with an 8.3 Cummings(all mechanical),36'.

Jim
1992 ORED, 36', White w/Stripe decal(getting old)
Cummings 8'3 Mechanical, 182561kmi. 3299hrs.
Build #4062

Re: Battery isolator

Reply #7 –
Dan, et al.:
 
Your battery isolator picture shows a yellow substance on the wire connections. I have also seen some with red/pink colored protectant. What is the difference in the two? Is one more preferable?
 
Thank you,
 
Trent

Trent and Jean Eyler
2000  U295  4003  WTFE  ISC  350
Build#5603 MC#17385

Re: Battery isolator

Reply #8 –
Quote from: TulsaTrent –
Dan, et al.:
 
Your battery isolator picture shows a yellow substance on the wire connections. I have also seen some with red/pink colored protectant. What is the difference in the two? Is one more preferable?
 
Thank you,
 
Trent





I can't help with what the yellow substance is. Our coach had it when purchased.
Dan - Full timing since 2009
2003 U320 40' Tag 2 slide
 

Re: Battery isolator

Reply #9 –

The colored protectant is what every the last person who serviced put on.  FT used something like that originally.  These shouldn't corode like battery terminals but you can get an electrically conductive grease that keeps them clean and dry from Bay Marine Supply or use CorrosionX on the studs, lugs, washers and nuts.  Doesn't take much of either.

NO-OX-ID "A Special" Conductive Terminal Grease

Amazon.com: Corrosion-X Corrosion Technologies 91002 Corrosionx 16 Oz....

Comes in smaller sizes and spray cans as well.

I use both. 👍👍


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Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN