Engine batteries not charging

Temp fix. Jumper the two big terminals on the isolator. leave it that way for 30 minutes to an hour then try to start. Remove jumper when done.

To use aux start Press and hold button 30 seconds. release 30 seconds repeat then press and try to start.

NOW: though many RV's (my 2005 for example) have a B.I.R.D. system (Bidirectional Isolator Relay Device) not all do even today.. It Sounds like yours is one of the "Does not have" (Though this is not the only option. I will cover two more options in a second)

The TRICK-L-Start device. 3 wires (the two big terminals on the Big Boy and a ground) is all it takes to hook 'er up.

The other posibilities
1: With my factory battery this happend 3 times. Dirty battery terminals. Symptom in my case I turned switch ot ON dash lit up normally. Turned to START and everything died.. Emergency start (Aux start) worked
Cleaning terminals. Fixed

2: A shorted cell in the battery will give results close to what you measured.

Disconnect the battery isolator from the starting battery.

Jump start the engine. Hold the engine RPM at "fast idle" (about 1500 RPM) and use a meter to check the voltage at the starting battery terminals. It should be OVER 13.8V ! If not, you have a loose/corroded connection between the starting battery and the alternator or a bad alternator.

If you have proper voltage withe the engine running, it is time for a new starting battery.

I had the same thing happen on my previous Bounder MH. Your description of the problem is exactly what happened on mine.

It was a failure of the solenoid in the Battery Control Center. When connected to shore power, it should engage, charging all batteries. When no shore power, it should disconnect, and isolate the chassis battery.

The auxiliary switch sends power to that same solenoid to connect the chassis battery to the house batteries, allowing you to start the vehicle if the chassis battery is dead. However, if that solenoid is the reason the battery never charged, sending power to it via the aux switch does nothing!

It's a PITA to fix, but not expensive, nor complicated. Here's how I fixed mine: http://2manytoyz.com/bcc.html

FWIW, our 2015 Forest River MH uses the same solenoid setup. Probably very similar on many makes/models/years.

As someone mentioned, you "can" use a heavy jumper wire between the chassis and house batteries on the BCC. I made an emergency jumper with 2 gauge wire just in case.

jaycocamper62301 wrote:
I have my 2006 Bounder 37U here at home in my shop and has been hooked up to shore power since Wednesday. House batteries are charging and chassis batteries are not. Now the RV won't start. Where do I start. I have a Big Boy battery isolator ad it has 13.4 volts on one post and 11.5 on the other. All interstate batteries are 2 years old

4 days and the chassis batteries won't start the engine is not related to the shore charger.

The rig should sit for a month+ and still start the engine with no shore power. Load test the batteries as even 2 year old batteries fail. Then cables, solenoid, starter or starter circuit. Or you may have a very high drain from somewhere. Voltmeters and ammeters (especially clamp on) are your friend.

You may/may not also have a shore charging problem but that doesn't solve the 4 day starting problem.

You could also have a alternator charging problem.

BTW I recently replaced my aging clampon with a Southwire from Lowes that has a variety of functions. If you're in the market for one be sure that it has DC amp capability as AC only is more common.

For reference:

Southwire 400 Amp AC/DC clampon meter – Lowes $72

Southwire 400 Amp AC/DC True RMS clamp meter combines the features needed for the professional electrician including True RMS readings, the ability to measure both AC and DC current, a built-in non-contact AC voltage detector, and multimeter, capacitance and temperature functions.
• True RMS readings provide accurate results on circuits with harmonic distortion
• Measures both AC and DC current for use in multiple applications
• Capacitance, frequency, duty cycle and temperature functions
• Built-in non-contact AC voltage detector
• Impact resistant double molded housing also provides comfortable grip
• CAT LED's 600 V
• UL Listed

jaycocamper62301 wrote:

RLS7201 wrote:
Close to the two battery banks is a black box called a Battery Control Center (BCC), manufactured by RV Custom Products. In the BCC, behind the circuit board, is the isolator relay. It's the silver one. It's probably your problem. On the back side of the BCC cover is a wiring print, that shows how the isolator relay connects the two battery banks together when either battery bank reaches 13.2 volts. Your coach DOES charge the chassis battery when plugged in. Advice about your charging system from non Fleetwood owners is usually incorrect.

Richard

so you're saying take the entire fuse panel out because there is no isolator relay there

Read more closely..........."In the BCC, behind the circuit board, is the isolator relay."

Richard

take the cover off the BBC
NOT your inside DC fuse panel

there one or more DC reset-able breakers aka little black boxes with buttons that stick out
reset the breaker, aka push in the little button

the relays are behind the circuit board of the BCC

the parts drawing with labels is on the inside face of the cover