Skip to main content ↑ ↓
Topic: battery isolator (Read 559 times) previous topic - next topic

battery isolator

I have a power line model PLI 190 - 3 Isolator in my 1992 Grandvilla.  I am replacing bad batteries and believe my isolator is shot.  I have read all (most) posts regarding the isolator and am pretty convinced I need a new one.
I have removed the house batteries and just have the starter battery in place.  The starter battery is only connected to the starter and the isolator.  Without a house battery all my 12 volt house fixtures still work - i.e. lights, 12 volt tv outlet, water pump.  This was my first indicator that I had a problem.  I tested the isolator and with no house battery I got a 12.5 volt reading from the house lug.  I also got a 12 .6 from the start battery lug.  Does this sound like a bad isolator.  Just double checking before I purchase another one. 

Thanks
Howard Reinhardt
Howard & Rose
92 U225 GV - 36'  - Build # 3989
2003 Honda Civic
95 Jeep Wrangler
2018 Winnebago Travato 59K
4 Chihuahuas

Re: battery isolator

Reply #1 –
The purpose of a isolator is to "isolate" the start battery from the house systems, so you can't discharge it to the point where it won't start the coach.  If your 12 volt house circuits are (apparently) being powered off the start battery, and there are no other batteries present, AND you are not powering the charger/converter by being plugged in or running your generator, then I would say "Yes" your isolator is toast.  Just my opinion, but I don't see any other explanation.  Wait for other "experts" to weigh in, as I'm sure they will.
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 #2 –
Thanks cajk - No other batteries present, not plugged in, and not running generator.  Left me with no explanation either.
Howard & Rose
92 U225 GV - 36'  - Build # 3989
2003 Honda Civic
95 Jeep Wrangler
2018 Winnebago Travato 59K
4 Chihuahuas

Re: battery isolator

Reply #3 –
If you are replacing batteries, and your coach still has the original factory installed charger/converter, then you should seriously consider getting a new "smart" replacement.  It will add years to the life of your new batteries, and contribute greatly to your "peace of mind".  Search the forum for product recommendations.
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 #4 –
I would also check the boost solenoid as it may have the contacts stuck together which would be keeping the house activated through it. Easy to check, just remove one of the large wires on the solenoid and see if the house is still activated. You could also do that with the isolator as well. How about solar.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: battery isolator

Reply #5 –
We we bought our U300, we went to a wedding and had the roof fan on all day. That night, both house and engine batteries were dead. I just jumped it to get it going but when we got home, I started looking at the schematic and discovered the isolator had been wired incorrectly. Super easy to make a mistake when changing isolators. After checking all the cables and their destinations against the electrical schematic, I recommend using a label machine to put the correct code and where the cable goes/comes from. There is a code on the cable but in this location, it usually fades so you can't read it.

Also possible as noted above, that the boost solenoid has failed.

I have the electrical schematic for '93 U300/U280 I can email. It may be close enough to help if you don't have yours.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: battery isolator

Reply #6 –
Quote from: red tractor –
I would also check the boost solenoid as it may have the contacts stuck together which would be keeping the house activated through it. Easy to check, just remove one of the large wires on the solenoid and see if the house is still activated. You could also do that with the isolator as well. How about solar.

A boost solenoid stuck on is a more likely fault than a shorted diode in the isolator, they usually open on failure.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: battery isolator

Reply #7 –
See, I told you you would get good advice from the more experienced members.  I'm still a rookie at this stuff.

I have a question about how you left your battery cables when you removed the coach batteries.  On my wiring diagram, the positive post of one of the coach batteries has 3 cables attached, labeled B3, B4 and B11.  If your setup is the same, then I'm wondering if you left those 3 cables connected to each other.  If so, then that is how the boost solenoid stuck in the "closed" position would be able to supply power to all the coach circuits.  A stuck boost solenoid would also explain why you got the same voltage reading on both battery posts on the isolator.  I think I'm gonna retract my initial opinion, and throw in with Ron's diagnosis.  Your isolator may be just fine.

I would do what Ron suggested - remove the big cable from the "coach battery" post on the isolator.  Then check voltage on both posts of of the boost solenoid.  If you get the same reading (start battery voltage) on both posts, the solenoid is bad.
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 #8 –
Thanks all.  Cajk - I have replaced the converter with a progressive dynamics intellipower 9100 series, with charge wizard.  Old one died a couple of years ago.

Red Tractor - I think you may have something there.  I used a wire to check the solenoid and did not get a clicking, so possibly the contacts are stuck.  Will do the testing as mentioned, thanks.

Good suggestion Pierce.  Would also love a copy of the electrical schematic - hjrein@aol.com.  Thanks.

Didn't think of the boost solenoid first - now its on the top of my list.  Thanks Tom

Appreciate the help - got some checking to do tomorrow.

Howard & Rose
92 U225 GV - 36'  - Build # 3989
2003 Honda Civic
95 Jeep Wrangler
2018 Winnebago Travato 59K
4 Chihuahuas