2018 Thor forewinds C Class House battery

[Billy2135]

Hello All,

I had to remove the house battery for storage, and it was dark, I was in a rush and forgot to take a picture of how the wires were connected. There are 5. 3 red and 2 black.

I assumed that the red would be positive and black negative. I hooked them up, got a spark from the negative terminal heard a noise which sounded like the auto leveling system, and then a click. I looked under to the right side of the battery box and the 2 black wires were connected to breaker modules, so I knew they would be positive. I reversed the wires on the battery, but now nothing happens. No power.

Did I potentially blow a fuse, or heaven forbid damaged my electrical system?

Some pics attached of my battery box and the black wires connected to the modules.

Thank you in advance.

Bill

[The Gritz Carlton]

Red Hot, Black Negative isn't always true with Thor. Trace the cables/wires to the end/device and see it its either. Others with same make and model may be able to help but nothing seems to be consistent from unit to unit at Thor.

[Chateau_Nomad]

I did a similar "oops" several years ago with a trailer battery. You probably just tripped the main battery breaker, and possibly a couple fuses in the main DC service panel.

Before replacing fuses, etc. start tracing the cables in the wire looms and see where they go. Don't even trust the colors of the cable jacket... anything is possible. Looks like you found the main breaker feed and a ground.

Those heavy cables will feed heavy amp devices like your generator starter, hydraulic jacks if you have those. You might need to do a continuity check if you can't fully visually trace the cables.

Once you get it all sorted, clean all cable ends and give a good coating of dielectric grease... as well as the battery terminals. Connect everything up and replace fuses, etc.

[Billy2135]

Thanks All.

Where would the battery breaker be located? I checked the main control panel, and none of the breakers were flipped.

Also, is there a possibility that I damaged the electrical system somehow or it should be ok? The labor fees are extremely high right now at the dealerships.

One more question: I need to run my generator with a load to prevent carb issues and rusting. There is an emergency button bottom right by the drivers side seat. How does this work? Do I start the main engine, hold it down for 5 minutes then manually start the generator?

Thanks,

Bill

[Beau388]

Originally Posted by Billy2135

Thanks All.

Where would the battery breaker be located? I checked the main control panel, and none of the breakers were flipped.

Also, is there a possibility that I damaged the electrical system somehow or it should be ok? The labor fees are extremely high right now at the dealerships.

One more question: I need to run my generator with a load to prevent carb issues and rusting. There is an emergency button bottom right by the drivers side seat. How does this work? Do I start the main engine, hold it down for 5 minutes then manually start the generator?

Thanks,

Bill

The 50 amp CB for the power center is located on the back of thwe entry steps (the drive shaft side). Usually?

There should be a 100 amp CB that supplies power to the jacks and the to start the generator. Note the chassis battery does not start the generator. The power comes from the house batteries

[Billy2135]

Originally Posted by Beau388

The 50 amp CB for the power center is located on the back of thwe entry steps (the drive shaft side). Usually?

There should be a 100 amp CB that supplies power to the jacks and the to start the generator. Note the chassis battery does not start the generator. The power comes from the house batteries

Thanks.

I understand under usual conditions that the generator uses the house battery, but there is an emergency generator control switch by the drivers seat on the left. I’m assuming this is used if the house battery is dead. Would make sense to have the generator not completely dependent on only 1 battery.

Any comment on the potential electrical damage?

[16ACE27]

Originally Posted by Billy2135

Hello All,

I had to remove the house battery for storage, and it was dark, I was in a rush and forgot to take a picture of how the wires were connected. There are 5. 3 red and 2 black.

I assumed that the red would be positive and black negative. I hooked them up, got a spark from the negative terminal heard a noise which sounded like the auto leveling system, and then a click. I looked under to the right side of the battery box and the 2 black wires were connected to breaker modules, so I knew they would be positive. I reversed the wires on the battery, but now nothing happens. No power.

Did I potentially blow a fuse, or heaven forbid damaged my electrical system?

Some pics attached of my battery box and the black wires connected to the modules.

Thank you in advance.

Bill

Yes, the two cables that go to the breakers go to the + post.

You have to trace out the other 3 cables to see which post they belong to.

At least one should go to the metal chassis frame (negative).

If you have an inverter one + should go to the inverter. There is also a - connection on the inverter that may go directly to ground (chassis) or back to the battery -. If the inverter - goes directly to ground, a second cable at the battery will probably go to ground.

You may also have a - cable that goes forward to the chassis battery through a Solenoid or BIM although that is often connected on the other side of the 100 amp breaker.

The 100 amp breaker goes to your generator and leveling system.

The 70 amp breaker goes to the House DC buss through the battery disconnect.

I would push the button to trip both of those breakers and reset them by pushing the flag back in.

The EMERGENCY START button bypasses the Solenoid or BIM (mentioned above) to join the house and chassis batteries to "jump" a weak chassis battery. It normally requires voltage on the house battery to operate. Sometimes there is not enough energy in the house battery to start the generator but there is enough to use the EMERGENCY START bypass to start the generator.

I would not attempt to use the EMERGENCY START function to start your generator until you get the battery wiring correct.

There are two large fuses in your power center (or on a stand-alone converter) that are REVERSE POLARITY PROTECTION fuses. You may have blown those if you hooked things up wrong

There are also small (5 amp) inline control fuses for the battery disconnect latching relay and the Solenoid/BIM that may have also blown.

[Billy2135]

Thank you kindly for your reply. If you can think of anything else, please let me know.

Bill

[Skip500]

Here is a picture of the battery in my 2018 Chateau 24f. Don’t know if this will help or not, sounds like you might have more things on your unit than I do. Good Luck! There are a lot of helpful folks here!

[Billy2135]

Good afternoon all,

I took another shot at figuring things out, and it seems like a bunch of fuses are blown. On the breaker panel, the 40 and the 10 are toast.

I went under the body of the motorhome to try and trace the 3 red wires, and it seems to be impossible as they go under, over and split in so many ways. I would have to take apart the whole motorhome to determine where they go.

Is there a devise I can hook up to use to determine where they go? I’m at a loss here.

Thanks I’m advance.

Bill

[Billy2135]

I removed the black sheath and determined that the “N” cable is black and all the rest are red. Does this mean that the red are positive and the one black is negative? Not sure how I would fit 4 on the positive post lol.

[16ACE27]

Originally Posted by Billy2135

Good afternoon all,

I took another shot at figuring things out, and it seems like a bunch of fuses are blown. On the breaker panel, the 40 and the 10 are toast.

I went under the body of the motorhome to try and trace the 3 red wires, and it seems to be impossible as they go under, over and split in so many ways. I would have to take apart the whole motorhome to determine where they go.

Is there a devise I can hook up to use to determine where they go? I’m at a loss here.

Thanks I’m advance.

Bill

Yes.

You can get one from Harbor Freight if you're in a hurry:

https://www.harborfreight.com/cable-tracker-94181.html

Or from Amazon if you want a better or cheaper "Cable Tracer" and can wait for delivery.

[barry.s]

To Billy 2135. The top photo shows incorrect hookup with battery terminals reversed. The next photo is correct. I wrapped red and black electrical tape on all the wires to identify them. Helps when another person fiddles with the battery as well.

[Billy2135]

Originally Posted by barry.s

To Billy 2135. The top photo shows incorrect hookup with battery terminals reversed. The next photo is correct. I wrapped red and black electrical tape on all the wires to identify them. Helps when another person fiddles with the battery as well.

Hello Sir,

Thank you very much for the reply.

How can you tell the second pick with the negative post near the 2 black/yellow cables and the positive terminal near the 3 red/black cables is correct? That’s how I hooked it up initially and blew the fuses. Please explain.

[barry.s]

Billy2135. Test the wires with an ohmeter when disconnected from battery. Clip one lead to the metal box around battery. The negative wires will have continuity to the metal box. The positive wires will show open circuit if everything is switched off. This is a general guideline but some exceptions may occur I suppose.

[Skip500]

In your first picture you have the positive cables hooked up to the negative post. In the second picture you reversed the battery and show the connections at the positive post even though they are not hooked up.

[16ACE27]

Originally Posted by Skip500

In your first picture you have the positive cables hooked up to the negative post. In the second picture you reversed the battery and show the connections at the positive post even though they are not hooked up.

How do you know which is positive and which is negative? Thor does not use the standard (or any) color coding system for battery cables.

[Skip500]

All I was saying, in the first picture he had most of the connections to the negative post!

[16ACE27]

Originally Posted by Skip500

In your first picture you have the positive cables hooked up to the negative post. In the second picture you reversed the battery and show the connections at the positive post even though they are not hooked up.

Originally Posted by Skip500

All I was saying, in the first picture he had most of the connections to the negative post!

If you say so.

[Billy2135]

Hi all,

I finally figured it out.

I replaced all the blown fuses, used a multimeter on the ohm setting. Placed the black probe on the bare metal battery case and tested each cable with the positive probe. The only cable that registered a sound and reading was the “N” cable so this meant that cable was negative. Hooked up the other 4 cables on the positive terminal and the N cable on the negative. Everything is good now and works fine.

I remembered 3 on the positive and 2 on the negative. Must be getting old. Lol

Thanks for all the help gentlemen.

Bill