chassis electrical issue

miles ahead · 04-22-2021, 06:11 PM

i have a 2018 S2RV 37HJ. I recently replaced the breaker that is above the batteries almost the middle of the frame that is hard to access. Now I have a problem with one of the positive leads from the chassis battery jumps about every 90 seconds. There are two positive leads, this is the smaller one. I isolated it to see that it only jumps with the engine running. can't find anything that isn't working but it is obviously being hit with a large power surge intermitently. I don't hear any clicking or other unusual noises when it jumps.
Has anyone else had this problem?

thanks in advance.

miles ahead · 04-24-2021, 08:48 AM

more info for post: it actually snaps and jumps every 20 seconds. I also can't find anything that isn's working.

craigav · 04-24-2021, 09:14 AM

I am fairly familiar with electrical systems and electronics, however I don't understand what you mean when you say the positive lead snaps and jumps. Perhaps you could give more details into what you are seeing, as doing so may be very helpful. ~CA

craigav · 04-24-2021, 09:22 AM

I think I may understand what you are talking about, the positive lead has moments of high amperage, likely led to ruining of the breaker you replaced (likely a self resetting breaker) and this amp surge you see happens when the engine is running, does that sound right? If so, I suspect you have another self-resetting breaker along that same circuit which connects into the engines alternator charging system, and the batteries are low enough to draw more current than that breaker can handle and therefore the surge in power, then the breaker breaks, once it cools down it reconnects and the cycle continues. One test you could possibly make is to charge up your coach batteries to 100% with an external charger (or your converter will do this with enough time) and then test again. It may be of value for you if you or someone here can share a wiring diagram as on my Class C (and I suspect yours could be similar) there are 2 self resetting breakers along the circuit from the engine's alternator to the coach batteries, (along with a relay). ~CA

miles ahead · 04-24-2021, 11:58 AM

i was able to ey liminate the problem by disconnecting the cable that runs from that circuit breaker to a relay on the other side of the battery tray. I believe that relay says "battery isolator." That relay has many wires running to and from it. from your previous information it appears that it may be caused by bad coach batteries? I did charge them overnight and they are showing 12.3 volts and the cable it still physically jumping every 20 seconds.

craigav · 04-24-2021, 01:41 PM

Bad batteries could certainly be the issue, they are likely pulling more charge amps from the alternator than the breakers are rated for. Generally speaking a fully charged battery should be closer to 12.8, however that voltage applies only if the batteries are at rest, in other words disconnected or no load on them (and best to wait 6 or more hours of rest), as a good battery fully charged can show less than that if there is a load on the battery. Does your Super C have an amp meter showing the charge rate on the dash? If so, I suspect it would be indicating a lot of alternator charge current. If you know your batteries are old anyway and the voltage didn't come up with a known good charger, I would replace them anyway as bad batteries certainly could cause the issue you are encountering. ~CA

miles ahead · 04-24-2021, 02:36 PM

I am currently charging the batteries but if they don't appear to be holding the charge I will replace. My Seneca does not show how amperage it is charging. Thanks for all the information!

RVermont · 04-24-2021, 06:24 PM

The Seneca’s use a BIM. Battery isolation module. This unit monitors both battery banks and if the voltage on one is a set point below the voltage on the other is closes and allow current to flow thus charging the lower bank. It sounds like you have a bad battery somewhere and this pulling all batteries down. There are posts on here that explain the operation of this and provides an electrical drawing of the 12 volt system and what ports what. I will see if I can located these and post the link.

RVermont · 04-24-2021, 06:48 PM

Here are some drawing. Hope they help. This is for my 2018 TS. I can not be sure they match your unit but should be fairly close

These did not seem to come out very well. I will see if I can reload them with better resolution.

miles ahead · 04-25-2021, 06:57 AM

Thanks again to all who contributed to this post. I understand basic electrical stuff but beyond that it is all a mystery to me. I believe my best option at this time is to replace batteries because they do not charge above 12.3 volts and drop pretty quickly and they are 3 years old. At least that way I can eliminate that problem and move on from there. I will post the results once I change batteries.

Thank you all.

Rustynuts · 04-25-2021, 10:59 AM

Here is the PDF of the BIM trouble shooting guide and a couple more wiring diagrams.

http://www.precisioncircuitsinc.com/...e-Shooting.pdf

miles ahead · 04-25-2021, 01:36 PM

Thanks for the additional schematics. Still testing voltage drop on batteries.

miles ahead · 04-27-2021, 09:25 AM

after fully charging both sets of batteries and letting them set for a day with out use and no charging and also isolating each individual battery, i discovered that they were all holding a charge, 12.6 for the house and 13 for the chassis, so I decided not to replace the batteries. I then connected all and found that my original issue of the positive lead snapping and jumping had disappeared. Apparently, it was caused by the house batteries being low on voltage. I am aware that they may be close to end of life and will keep a close watch on them.

Thanks again to all who responded to this post. I could not have fixed the problem without all your help!

You may also like: