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Topic: 2005 U270 charging problem (Read 265 times) previous topic - next topic

2005 U270 charging problem

Helping Dave with a house battery charging problem,alternator putting out 13.7 volts,all connections and batteries good,have 13.7
going into isolator,13.7 going to start batteries,12.3 going to house batteries,house batteries are 1 year old standard batteries.Thinking the isolator is bad,when he turns on the boost switch both outputs of the isolator go to 13.7.Any other ideas?
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: 2005 U270 charging problem

Reply #1 –
What kind of isolator:

Diode based?  If so, what are voltage readings at center lug and the two outer lugs with engine around 1.100 RPM?

Solenoid/relay based?
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: 2005 U270 charging problem

Reply #2 –
Diode based,looks like a Cole Hearse but no label,13.7 at center,13.7 at start battery,12.3 at house battery post,is 3 post isolator.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: 2005 U270 charging problem

Reply #3 –
Indeed, bad isolator.

But a little confusing: Reading on center lug (direct connection to alternator B+ terminal should be about .7 VDC higher than the two readings on the outer lugs (one to each battery bank).  That .7 VDC loss is turned on to HEAT.  That is why the diode-based isolator has the fins-- to dissipate the heat. You posted same readings for center and chassis battery lugs??

Short term fix would be to move the cable from the house post and add it to the lug for the chassis  battery.  Note: batteries will not only charge together, but will also discharge together.
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: 2005 U270 charging problem

Reply #4 –
Will remeasure the voltage,thanks,got the message.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: 2005 U270 charging problem

Reply #5 –
Thank you Brett & Dave! It was definitely the isolator, will replace next week.
Dave & Danette
2005 Foretravel U270, 3620 PBLW, Build #6331
2018 Jeep Grand Cherokee
2017 Can-Am Maverick X3 RR
2016 Polaris Turbo RZR
Motorcade #17839

Re: 2005 U270 charging problem

Reply #6 –
Dave,

If you need to travel before replacing it, let us know.  Several easy work arounds for a failed isolator.
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: 2005 U270 charging problem

Reply #7 –
Quote from: wolfe10 –
Dave,

If you need to travel before replacing it, let us know.  Several easy work arounds for a failed isolator.

No hurry, we're in Arizona till mid March. I was running the generator to keep them charged when the isolator went out.
Dave & Danette
2005 Foretravel U270, 3620 PBLW, Build #6331
2018 Jeep Grand Cherokee
2017 Can-Am Maverick X3 RR
2016 Polaris Turbo RZR
Motorcade #17839