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House battery drain with engine running

Yahoo Message Number: 77631
Today while driving I became aware that there was a 25-30 amp drain on our house batteries. Normally the batteries charge while driving. While still driving I turned on the generator and that overcame the drain and pushed the charge rate up to a positive 60 amps instead of the usual 90 indicating that there was still a drain of 30 amps or so coming from somewhere. When we shut off the engine the current drain went away so it was associated with the engine running and not with anything drawing on the house batteries from within the coach. Suspicions immediately go to the engine alternator charging circuit. What can I check and how should I check it?? Cummins ISL 370. Thanks for your help. (520-907-6379) Steve B - Intrigue #11382

Re: House battery drain with engine running

Reply #1 –
Yahoo Message Number: 77632
Hi Steve - Not an expert on electrical (DW reminds me I'm not an expert on most things:)!), but with the generator off, could you not read the charge coming to the chassis battery to confirm it is a 'negative draw'? This would validate that your on the right track with the alternator research.
Have you looked to confirm all the belts are in place? (I can't recall if our ISL370 has a separate belt for the alternator, or just one big one for all belt related activity.)

I wish you luck on your hunt, and will follow the post to learn.
Best,
Smitty

04 Allure 31017
04 Allure Sold to a nice new owner! Now enjoying a 07 Magna Rembrandt 45' ISX600 #6775
"We're ONDROAD for THEJRNY!" (Toad and Coach license plates, say Hi if you see us!)

Re: House battery drain with engine running

Reply #2 –
Yahoo Message Number: 77635
I've checked the belts and all is well (large serpentine belt drives alternator). I checked the voltages at the chassis and house batteries with the engine off and with the engine on. The chassis battery voltage drops from 12.40 with the engine off down to 12.25 when the engine is on. Similarly the house battery voltage drops from 12.60 with the engine off down to 12.45 with the engine on. We know that it shouldn't do that!!! I can understand the alternator not putting out but I wouldn't have suspected it to actually be a drain.
Steve

Re: House battery drain with engine running

Reply #3 –
Yahoo Message Number: 77638
A DC clamp on ammeter is a test tool that.some RV's carry and electrical trouble shooters This meter enables DC current to be traced and the direction determined This is different than an AC clamp on meter Bob 06 intrigue 12047

Re: House battery drain with engine running

Reply #4 –
Yahoo Message Number: 77640
OK, I happen to be one of those RVers who carry a DC Clamp-on Ammeter. Can you suggest some test points or lines where I should be checking? Steve

Re: House battery drain with engine running

Reply #5 –
Yahoo Message Number: 77644
Start with the alternator leads with the engine running and not running Then the two chassis battery leads then the two house batteries again with the engine running and not running lead access my difficult record the info draw a component sketch one with the engine running and the other not running and then decide on the next test BOB
 

Re: House battery drain with engine running

Reply #6 –
Yahoo Message Number: 77673
A follow up and thanks to all who provided comments and inputs to our charging problem. All the house batteries and the coach battery were load tested and were good. Voltage measurements at the batteries and the alternator indicated a bad alternator. The original Leece Neville alternator (Model A0012824LC) was replaced by the same model alternator by Colton Truck Terminal in Colton, CA and the charging circuit sprang to life with my Link 10 E-meter showing better than 50 amps of charging at engine idle. I haven't seen that much charging out of the alternator for a long time. I should have suspected that the alternator was growing weak as the charging rate while running has been slowly getting less and less until suddenly it went away completely.
Explanation for why there were over 30 negative amps on the house batteries while running was that with no charge coming from the alternator, the chassis battery was sucking power from the house batteries while the engine was running to run all the chassis related items.

Thanks again to all who chimed in with advice.

Steve B

2002 Intrigue #11382