Not charging while driving

[Dom101]

2017 Seneca 37TS
MH is not charging coach batteries while driving. there is 12v to the coach battery side of isolator but not to the chassis side of isolator. I tried following cable but is goes into the abiss. Has anyone else experienced this or have any ideas? With ignition on I get 12v to the isolator itself

 

[Rustynuts]

These BIM units do fail but can be tested. I have attached the wiring diagram of the BIM and the troubleshooting document for testing. If it has failed, that style is no longer available and can be replaced with the pictured unit from Precision Circuits. It is a wire for wire swap except the generator wire is left disconnected and capped off.

 

[Dom101]

Hot damn I wish you were my neighbour . Do you know where is battery cable on the battery side of isolator goes to? Their is no power to it. The isolator seems to work as I get 12v to the switching leg. The large battery cable goes into the wire loom in the MH. I think I traced it down to the genny but I can't be sure.

 

[Rustynuts]

One side of the main lug goes to the chassis batteries and the other goes to the coach batteries, Here is a drawing showing the newer model of BIM but the connections are the same. Both large cables run through a breaker that may be tripped.

 

[Dom101]

Thanks I'll see if I can locate those breakers. Sounds like this is where the break is

 

[SloPoke-TC]

2017 Seneca 37TS
MH is not charging coach batteries while driving. there is 12v to the coach battery side of isolator but not to the chassis side of isolator. I tried following cable but is goes into the abiss. Has anyone else experienced this or have any ideas? With ignition on I get 12v to the isolator itself

Sounds like you may have tripped the breaker on top of the chassis batteries. Open the drivers side door, Pull the cover under the drivers seat. There are two small auto-reset circuit breakers and a large 100A breaker that has a small lever that has to be pushed back in. I circled the breaker in the attached schematic.

 

[SloPoke-TC]

The breaker is Circled in blue

 

[Dom101]

Opps I saw the diagram but didn't read the txt above it. Dum. Will check it tomorrow.
Thanks

 

[Dom101]

Up date. My unit doesn't have breakers on top of the batteries, but I did find something on the sidewalls that look like breakers and there is power going through.
In the picture now I am getting 12v from the hot on the coach battery indicated in blue, to the two points indicated in yellow. the bigger cable (red) says its chassis battery. This indicates it is on the negative side, as I wouldn't get 12v from positive coach terminal to it. Does this make sense?

 

[craigav]

The 12v you are reading can be confusing for sure. However, the 12v reading does not mean that the yellow connections are negative cables or connected to the frame ground, instead you are simply completing the circuit which means that they are connected to components that do have a connection to those points and back to the negative and that the yellow point cables do not have 12v+ in them. ~CA

 

[Dom101]

Ya I was thinking something like that. Enough to trigger a meter through windings or similar. That large red cable that should have 12v positive, and doesn't, heads toward the rear of the coach, but I have no idea where.

 

[craigav]

BTW as a test, with the key off, have someone press the Aux Boost switch while you listen to the BIM as it should click. Also if you don't hear a click then check the power 12v to the "signal" connection which should have power when the key is on or the boost button is pressed. If you don't hear a click and there is voltage on the signal wire when the boost button is pressed or the key is on then you have a bad BIM, if you don't have voltage on the signal wire when either the boost button is pressed or when the key is on, then the failure is that the BIM is not getting a signal to close (connect). ~CA

 

[Dom101]

Sorry for the late response. We packed up and came camping yesterday. So aux battery switch does work as that's how i can get steps to close when unplugged. But it's weird that I don't get any voltage on the large positive cable that goes to the chassis battery. Yet if it works on the auxiliary switch on the dash it must be going through that cable. Does that make sense

 

[SloPoke-TC]

Sorry for the late response. We packed up and came camping yesterday. So aux battery switch does work as that's how i can get steps to close when unplugged. But it's weird that I don't get any voltage on the large positive cable that goes to the chassis battery. Yet if it works on the auxiliary switch on the dash it must be going through that cable. Does that make sense

yes it makes sense... as that cable is going to the circuit breaker that is mounted on top of the chassis batteries. The large lugs on the battery (BIM) relay go to each of the battery banks... one to the house batteries and the other to the circuit breaker that is connected to the chassis batteries. When you engage the BIM relay with the dash push-button, it then passes power to that side of the chassis battery breaker that also is connected (powers) the steps, cord reel and leveling jacks.

you will find different behaviors when the ignition is on, as it also energizes the BIM relay to charge the house battery from the engine -- BUT not if the breaker on top of the chassis batteries is tripped

 

[Dom101]

So there isn't a breaker on top of the batteries on this model, their is one
On the side wall and it is good. The fact that the isolator switch on dash closes the isolator, lends me to believe that the isolator is good but then again,I'm not sure. It could be the switching wire that isn't getting 12 volts i have checked any fuses i can find but must be missing something

 

[Dom101]

Thanks to Rusty it's i have good wiring diagrams which i can use when I get home. But in the mean time can anyone foresee any problems with a 30 amp fused jumper between the chassis lug on isolator and coach lug for driving home?

 

[Robbbyr]

So there isn't a breaker on top of the batteries on this model, their is one
On the side wall and it is good. The fact that the isolator switch on dash closes the isolator, lends me to believe that the isolator is good but then again,I'm not sure. It could be the switching wire that isn't getting 12 volts i have checked any fuses i can find but must be missing something

Have you checked for a breaker on top of the chassis batteries? Every M2 Seneca I have seen has a large breaker mounted to the battery hold-down bracket.

 

[Kevin Cooper]

Thanks to Rusty it's i have good wiring diagrams which i can use when I get home. But in the mean time can anyone foresee any problems with a 30 amp fused jumper between the chassis lug on isolator and coach lug for driving home?

I installed a 30 a resettable circuit breaker connected to the two terminals of the Aux start solenoid. My chassis battery would run down in a week. So, I put it in to charge chassis while plugged into shore. There is one issue though. If your house batteries are way down, your alternator can put over 50 amps to the house batteries.
If you have chassis and house power on the two posts, and do not let your house battery go down to 10 volts or less, then you will have no problems with the 30 amp.
This is similar to what I have installed.
BULVACK 30 Amp Circuit Breaker for Boat Trolling Motor Marine ATV Trailer Vehicles Stereo Audio Electronic Battery Solar System Inline Fuse with Manual Reset Switch Waterproof DC 12V-48V (30A) Amazon.com

 

[SloPoke-TC]

One final comment / question before considering this thread abandoned. And these comments are limited to the M2 chassis Seneca's (before 2018 1/2) There are systems on the coach that are essential for the chassis operation of the vehicle that are powered primarily by the chassis batteries -AND- systems in the coach that are powered by the House Batteries that are more related to the interior of the living space.

Jacks are needed to be retracted for the vehicle to be able to move, Stairs need to be retracted for the vehicle to move and the power cord needs to be retracted too... They all work even if you have the master disconnect switch shutting down the power of the inside of the motorhome, and the Jacks/Stairs/CordReel (SJC) all work even if the house batteries were removed. They get their power primarily from the chassis batteries after passing thru a 100A circuit breaker that is mounted in the chassis battery compartment under the drivers seat. After the 100A breaker, power is split off to the Jacks and Stairs with smaller wires that are protected by some smaller self-resetting circuit breakers mounted adjacent to the 100A breaker.

So, if the Engine is off - and the Shore power is disconnected - and the generator is off... Are the steps/jacks/cord-reel(SJC) working? They are powered by the chassis batteries. If they are not working, you can test this further by engaging the BIM override switch on the dash to check if these start to work. If it does, then the BIM is passing power on the chassis battery cable that is connected on the same terminal as the SJC on that 100A breaker in the chassis battery compartment.