Generator only runs while Sprinter is running

[gks314]

This is a new issue on my 2017 Midwest Auto Sprinter Weekender, with an LP Onan 2800 generator.

Everything was working fine until I had the starter battery replaced at a national chain. Beginning immediately afterwards, the generator will not start unless the RV is running. And once the generator IS running, it shuts off instantly when the RV is turned off.

This happens even when connected to shore power.

While the generator is running, it supplies AC power to the RV just as before, running the air conditioner or microwave, for example, without problems. While running, the generator also charges the house batteries just as before.

In other words, the genny seems to be behaving normally once running, but it will only run if the RV itself is running.

What could have happened during the starter battery replacement to explain this behavior?

All fuses and breakers appear to be good.

Thanks in advance,
--Greg

[GeorgeRa]

I would inspect wiring of the starter battery in the footwell, any loose wires? Who replaced the battery?

Edit: Did you see them replacing the battery? Did they remove the driver seat to access the wiring under the seat?

[mkguitar]

"starter battery"



you mean the battery for the van or the battery for the "coach"


this is weird




possible 2 problems



1 is with the coach battery supplying power, the other with the battery isolator...?

[gks314]

Originally Posted by GeorgeRa

I would inspect wiring of the starter battery in the footwell, any loose wires? Who replaced the battery?

Edit: Did you see them replacing the battery? Did they remove the driver seat to access the wiring under the seat?

Done at NTB.
I did inspect it (I could have SWORN I had a pic too), and the cables looked snug to the terminal. There is a yellow wire that runs across the battery (under the cover, in the battery box) that goes from the front of the vehicle to the rear (or vice-versa). Cannot see where it is connected, but it doesn't feel loose.

I did not see them replace it (but I had to show them where it was and how to get to it) and I am sure they did not do anything with the drivers seat

[GeorgeRa]

"Beginning immediately afterwards, the generator will not start unless the RV is running. And once the generator IS running, it shuts off instantly when the RV is turned off.
This happens even when connected to shore power."


Are referring RV is running to main battery disconnect on/off?

"While the generator is running, it supplies AC power to the RV just as before, running the air conditioner or microwave, for example, without problems. While running, the generator also charges the house batteries just as before."

How do you know house batteries are getting charged?

[gks314]

Originally Posted by mkguitar

"starter battery"



you mean the battery for the van or the battery for the "coach"


this is weird




possible 2 problems



1 is with the coach battery supplying power, the other with the battery isolator...?

What I meant by the replaced battery is that I replaced the "Mercedes" part, under the driver's floorboard, the one that starts the van's engine. I had heard this is called the "starter" battery, but I could very, very easily be using the wrong terminology.

There is a separate deep-cycle lifeline in the very rear which I have been (maybe incorrectly) referring to as the "house" battery. (Honestly, I'm new at this).

A. 1 is with the coach battery supplying power: The coach (or house, as I was thinking) battery does not seem to be showing any issues. All the electronics (tv's, radios, fridge, internet router, etc all seem to be running fine off of just the coach/house battery (or off of shore power).

B. Battery isolator:i don't think I know what this is. But I'll look it up

[gks314]

Originally Posted by GeorgeRa

"Beginning immediately afterwards, the generator will not start unless the RV is running. And once the generator IS running, it shuts off instantly when the RV is turned off.
This happens even when connected to shore power."


Are referring RV is running to main battery disconnect on/off?

"While the generator is running, it supplies AC power to the RV just as before, running the air conditioner or microwave, for example, without problems. While running, the generator also charges the house batteries just as before."

How do you know house batteries are getting charged?

1. I'm sorry, but I don't understand your question about main battery disconnect on/off.


2. There is a Freedom HFS inverter/charger in the van, and its (remote, in this case) display panel shows when the house batteries are being charged. In both shore power and generator power, it shows if it is charging the batteries (by saying bulk, absorb, or full) and by changing the indicator light from yellow (battery power) to green (indicating shore or battery power). I'm confident (though of course I could be wrong) that the house batteries are being charged by both the gen and by shore power

[GeorgeRa]

Originally Posted by gks314

1. I'm sorry, but I don't understand your question about main battery disconnect on/off.


2. There is a Freedom HFS inverter/charger in the van, and its (remote, in this case) display panel shows when the house batteries are being charged. In both shore power and generator power, it shows if it is charging the batteries (by saying bulk, absorb, or full) and by changing the indicator light from yellow (battery power) to green (indicating shore or battery power). I'm confident (though of course I could be wrong) that the house batteries are being charged by both the gen and by shore power

What do you mean by this statement "RV is turned off"?

Did you get an electric diagram from Midwest Auto? Is engine alternator charging house batteries when you run the engine? Perhaps Midwest wired your house batteries to starter battery via some kind of device inside the battery box and starter battery installers made changes. Your Sprinter schematic would help a lot to diagnose the problem.

[hbn7hj]

Haven’t we been through this before? Didn’t the ground lead from coach battery to chassis become disconnected?

[GeorgeRa]

It is possible, but, the negative post on the Sprinter battery has only one cable connection. If this would be disconnected car wouldn’t start. As far as I know there no other negative cables in vicinity of the battery box unless Midwest did something innovative or NTB (battery folks) did something other than replacement battery.

[hbn7hj]

The ground is missing from the coach battery, not the starting battery. When the ignition is turned off it no longer receives 12 volt power (2 amps) from a battery and ceases to run.

Shouldn’t be too difficult to solve. Find a way to start the generator with the ignition off. To do that you need to have 12 volts to the generator 12 volt connector. The generator 12 volt line is connected directly to the 12 volt pole of the coach battery, no fuse, no breaker. Get the negative pole connected to the generator frame and things must work.

[GeorgeRa]

Originally Posted by hbn7hj

The ground is missing from the coach battery, not the starting battery. When the ignition is turned off it no longer receives 12 volt power (2 amps) from a battery and ceases to run.

Shouldn’t be too difficult to solve. Find a way to start the generator with the ignition off. To do that you need to have 12 volts to the generator 12 volt connector. The generator 12 volt line is connected directly to the 12 volt pole of the coach battery, no fuse, no breaker. Get the negative pole connected to the generator frame and things will work.

I see your point; the question is what starter battery installer was doing with coach batteries. Coach battery to ground connection shouldn’t be near starter battery in the Sprinter.

[hbn7hj]

Originally Posted by GeorgeRa

I see your point; the question is what starter battery installer was doing with coach batteries. Coach battery to ground connection shouldn’t be near starter battery in the Sprinter.

Can’t answer that but the coach battery, either ground, power, or both is not connecting to the generator through a heavy wire. The coach battery could be bad but I think they checked that.

A half bright person with a volt ohmmeter should be able to solve this.

I suspect there will be a surprise when they figure out what happened to the ground (or the power). Can’t imagine what that is gonna be.

I’ll be in Dallas next Thanksgiving to enter the half bright contest if they haven’t got it fixed.

George, I have no doubt you could find the problem in a few minutes if you were hands on.

[JonK]

I don't know how this might create the problem being experienced. The cause is somehow related to replacing the vehicle battery, is is possible that the battery installer didn't register the new battery on the vehicle computer so the battery controls are wonky?

[skunberg]

Originally Posted by JonK

I don't know how this might create the problem being experienced. The cause is somehow related to replacing the vehicle battery, is is possible that the battery installer didn't register the new battery on the vehicle computer so the battery controls are wonky?

I would not assume it must be from the battery replacement. A different issue could be noticed after work is done without being related at all.

[markopolo]

Originally Posted by hbn7hj

The ground is missing from the coach battery.....................

That really does seem to be the most likely answer to solve this problem.

There must be two wires coming off the house battery negative post. One wire goes to the charger & DC panel etc. The second would go to the vehicle chassis and it wasn't reconnected. That's why everything else still works.

The house battery must not be charging when the Sprinter engine is running. That's easy enough to check.

Look for a disconnected wire near the house battery. It should be a thick wire.

It's a good practice to disconnect all negative/ground wires from all batteries when working on a coach so that's probably what happened.

[GeorgeRa]

The starter battery ground is connected via quick disconnect to the ground stud above the gas pedal. This is Sprinter’s main battery disconnect.
Without a Midwest electric diagram troubleshooting is difficult. I agree that anyone with basic understanding and a multimeter will diagnose it quickly.
If you didn’t notice yet gks314 is MIA.

[booster]

I am not up on Sprinter wiring, so could be way off.


In the past haven't they had the starting battery under the front seat and the coach batteries under the hood in some brands? If so, I would think it would be very common for people to think the ones under the hood were for starting.

[GeorgeRa]

The Sprinter starter battery is at the driver seat under the floorboard with a single ground connection to quick disconnect stud above the gas pedal. See previous picture.

Positive connection from the starter to the house battery is on the terminal located under the driver seat. The factory connecting relay is also connected under the driver seat. Access requires seat removal.

A factory auxiliary battery is located in the left side of the engine bay. Battery’s ground is connected to the ground terminal on the inner fender. Battery’s positive is connected to the terminal under the driver seat.

Linking the starter battery replacement with the generator failure is rather unlikely, unless, Midwest didn’t follow MB guidelines or whoever replaced the battery did something really wrong.

The attached document is old but likely still valid.

[GeorgeRa]

Originally Posted by booster

I am not up on Sprinter wiring, so could be way off.


In the past haven't they had the starting battery under the front seat and the coach batteries under the hood in some brands? If so, I would think it would be very common for people to think the ones under the hood were for starting.

Good point, but this mistake wouldn't fix the original problem with the starting battery which needed to be replaced.