Electrical Problem

manfromwahoo

New member
We have a 2019 Unity IB with a 2018 MB chassis. Less than 5,000 miles on it. And we have an electrical problem. We have been parked for about 3 weeks. We used the dash radio a few times and I think that we could have wore down the engine battery. Just before we noticed that there was a problem we had issues with our side entry dead-bolt (sticking) not retracting when using the key fobs. Suddenly, we had no seize noise when key inserted into ignition and the key will not turn in it, the key fobs won't work at all, and all dash lites are out. Upon the advice of LTV warranty service I charged the battery using a 1.5 amp trickle charger. The new charger only took about 5 hours to bring the battery up and then it indicated that it was in float mode. I left it on for another 20 hours and it was still in float mode. The key still wouldn't turn in the ignition. I'm confident that the charger did it's job but I haven't opened up the floor to check out the battery. ???
 

woundedpig

2018 Unity MB
Do you have a multimeter? You can measure the chassis battery voltage from the jump points under the hood. In our coach, there is about a 0.1 volt difference between the measurement at the jump points vs the battery terminals themselves, so there should be no problem diagnosing a dead battery by measuring at the jump points. Hard to believe the 1.5 amp trickle charger could charge a very dead chassis battery. Can you get a jump start? Or do you have access to a higher amp charger?
 
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csmithgator

2012 LTV Unity IB
We have a 2019 Unity IB with a 2018 MB chassis. Less than 5,000 miles on it. And we have an electrical problem. We have been parked for about 3 weeks. We used the dash radio a few times and I think that we could have wore down the engine battery. Just before we noticed that there was a problem we had issues with our side entry dead-bolt (sticking) not retracting when using the key fobs. Suddenly, we had no seize noise when key inserted into ignition and the key will not turn in it, the key fobs won't work at all, and all dash lites are out. Upon the advice of LTV warranty service I charged the battery using a 1.5 amp trickle charger. The new charger only took about 5 hours to bring the battery up and then it indicated that it was in float mode. I left it on for another 20 hours and it was still in float mode. The key still wouldn't turn in the ignition. I'm confident that the charger did it's job but I haven't opened up the floor to check out the battery. ???
We had a similar situation with totally dead chassis battery, trickle charger didn’t work. As Woundedpig suggested, we had to get a jumpstart to get our Unity running.
 

Aqua Puttana

Poly - Thread Finder
... I'm confident that the charger did it's job but I haven't opened up the floor to check out the battery. ???
Basics are always worth the time.

I would expose the chassis battery and check the voltage right at the terminals.

That will also give a good opportunity to attach the charger right to the battery terminals. (FWIW. I agree that a 1.5 amp charger would not normally drop down to "Float" after just 5 hours. That said, it could if the battery weren't too badly drained down. A heavier duty charger would be a better choice though.)

Parked for 3 weeks...
I assume that there is an OEM battery disconnect switch. Have you checked that the disconnect switch didn't get disturbed?

:2cents: vic
 

alichty

2014 LTV Unity TB
Agree with the responses above - a completely dead chassis battery needs a lot more than a trickle charger to fire up the MB diesel. I have dealt with a dead chassis battery and my own chargers (typical trickle chargers) weren't even vaguely up to the task. Neither was a direct jumper cable connected to a BMW 3 series jumper terminals.

Are you still under the factory CoachNet coverage or have AAA? They can send someone out with some serious enough external juice to scrape your chassis battery off of the floor. Been there done this and it works.
 

SSTraveler

2014 LTV Unity Murphy Bed
Once you get your chassis battery sorted out and working again you should consider adding a method to ensure the chassis battery is maintained from the house side (solar or shore power) so you don't have to worry about running your chassis battery down again. The most popular additions (for people who have FLA or AGM batteries for house and chassis batteries) are either a Blue Sea ML-ACR or a Trik-L-Start. Here are threads that provide a lot of details on either method, https://sprinter-source.com/forum/showthread.php?t=45224&highlight=Chassis+battery or https://sprinter-source.com/forum/showthread.php?t=35862&highlight=Chassis+battery.
 

kmay

2013 Unity MB
Agree with the responses above - a completely dead chassis battery needs a lot more than a trickle charger to fire up the MB diesel. I have dealt with a dead chassis battery and my own chargers (typical trickle chargers) weren't even vaguely up to the task. Neither was a direct jumper cable connected to a BMW 3 series jumper terminals.
My chassis battery was at 4.9v while in storage (long story) and it took 20 hours with a 2 amp charger to get a green light. Jumping from a Dodge Grand Caravan took too long.

I have been leery of starting a vehicle while the donor vehicle is running due to voltage surge. I have replaced alternator regulators and whole alternators following such events. My practice is to run the donor vehicle 20 minutes or so and then shut off. Start the recipient. It was suggested that this was no longer required, but I have not verified it with authoritative source.

Here is another caution, don't try to start with a weak battery. Think Yoda, no try - only do. The rapid system cycling on and off with low voltage may end up with one or more trouble codes. Happened at the storage lot and then on another occasion at the 'Benz dealership! I check voltage first if I suspect it may be low.

I am working on a solution to address the phantom draw when the battery is disconnected. At present, I have a 40w 2.2 amp briefcase solar panel on the chassis battery as a temporary solution. Works well for now.

I tried a 400ma panel that did not work. The instruction manual stated no worries about overcharging as 400ma could not harm a battery. Reading between the lines, I don't think the smaller panel has a controller and it could have pulled power from the battery at night.
 

autostaretx

Erratic Member
I tried a 400ma panel that did not work. The instruction manual stated no worries about overcharging as 400ma could not harm a battery. Reading between the lines, I don't think the smaller panel has a controller and it could have pulled power from the battery at night.
Simply put a diode in series with the 400ma panel, and it will prevent back-flow.

(for folks who find other numbers on their panels, 400ma works out to about 5 or 6 watts)

--dick
 

manfromwahoo

New member
Do you have a multimeter? You can measure the chassis battery voltage from the jump points under the hood. In our coach, there is about a 0.1 volt difference between the measurement at the jump points vs the battery terminals themselves, so there should be no problem diagnosing a dead battery by measuring at the jump points. Hard to believe the 1.5 amp trickle charger could charge a very dead chassis battery. Can you get a jump start? Or do you have access to a higher amp charger?
I don't think that a jump start is possible when the key will not turn in the ignition. Or, are you saying that a jump start jolt will suddenly resurrect the inoperable ignition?
 

manfromwahoo

New member
Basics are always worth the time.

I would expose the chassis battery and check the voltage right at the terminals.

That will also give a good opportunity to attach the charger right to the battery terminals. (FWIW. I agree that a 1.5 amp charger would not normally drop down to "Float" after just 5 hours. That said, it could if the battery weren't too badly drained down. A heavier duty charger would be a better choice though.)

Parked for 3 weeks...
I assume that there is an OEM battery disconnect switch. Have you checked that the disconnect switch didn't get disturbed?

:2cents: vic
The battery disconnect next to the pedals did not become disconnected.
 

manfromwahoo

New member
Thanks for all of the input. I have another question. Does disconnecting the battery disconnect next to the floor pedals have the same effect as disconnecting the negative battery terminal from the actual engine battery beneath the pilot's floor? i.e. supposedly reset the system?
 

Klipstr

2018 Wonder FTB
If you don't have anything directly connected to the battery positive. Scarecrow is working an issue where maybe that happened. As he told us when we picked up his rig in SLC the disconnect was engaged but the chassis battery was still quite dead. He suspects the installation of the new radio unit might be the culprit as he already replaced the chassis battery once. I know from my own experience that disconnecting at the gas pedal resulted in exactly the result wahoo expects. If you haven't had anything new installed on can assume the disconnect actually disconnects!
 

TJLee089

2013 Itasca Reyo 25R
Not sure exactly what you mean, but if the battery negative is truly disconnected, there can be no current and it doesn't matter if anything is directly connected to the battery positive.

If you don't have anything directly connected to the battery positive. Scarecrow is working an issue where maybe that happened. As he told us when we picked up his rig in SLC the disconnect was engaged but the chassis battery was still quite dead. He suspects the installation of the new radio unit might be the culprit as he already replaced the chassis battery once. I know from my own experience that disconnecting at the gas pedal resulted in exactly the result wahoo expects. If you haven't had anything new installed on can assume the disconnect actually disconnects!
 

Klipstr

2018 Wonder FTB
Yes, that is correct. What I meant was that if you use the positive disconnect by the gas pedal in the cab you may or may not get all the loads disconnected. If you disconnect the negative at the battery you most certainly get all the loads disconnected. Sorry for the confusion.
 

mikeme

2015 LTV IB: 2015 3500 V6
Yes, that is correct. What I meant was that if you use the positive disconnect by the gas pedal in the cab you may or may not get all the loads disconnected. If you disconnect the negative at the battery you most certainly get all the loads disconnected. Sorry for the confusion.
On the Sprinter, the disconnect by the accelerator is directly connected to (and only to) the negative terminal of the battery. In fact, if you pull the floor cover and access the battery, you can disconnect the negative terminal from the battery and see that the the disconnect wire is only a foot and half long and goes only to the negative terminal of the battery.
 
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TJLee089

2013 Itasca Reyo 25R
As Mikeme implied, there is no need to ever disconnect the negative at the battery unless an additional negative lead has been added there.

Yes, that is correct. What I meant was that if you use the positive disconnect by the gas pedal in the cab you may or may not get all the loads disconnected. If you disconnect the negative at the battery you most certainly get all the loads disconnected. Sorry for the confusion.
 

manfromwahoo

New member
Problem solved. As it turned out, a new multimeter showed me that my brand new 1.5 amp Schumacher charger/Maintainer was defective. So, I returned the defective 1.5 amp and bought a 3 amp Schumacher. Hooked it up to the contacts under the hood and 15 hrs later the ignition freed up. Finished it off through the cigarette lighter.
Thank you all for your help. A real learning experience for me.
 

woundedpig

2018 Unity MB
A real learning experience for me.
Multimeters are nice to have. We carry one on the road. Great for troubleshooting, making sense of things, not just from voltage measurements. I have been able to diagnosis blown fuses that did not look blown and an AC breaker that had failed.
 

woodywesty

New member
We have a 2019 Unity IB with a 2018 MB chassis. Less than 5,000 miles on it. And we have an electrical problem. We have been parked for about 3 weeks. We used the dash radio a few times and I think that we could have wore down the engine battery. Just before we noticed that there was a problem we had issues with our side entry dead-bolt (sticking) not retracting when using the key fobs. Suddenly, we had no seize noise when key inserted into ignition and the key will not turn in it, the key fobs won't work at all, and all dash lites are out. Upon the advice of LTV warranty service I charged the battery using a 1.5 amp trickle charger. The new charger only took about 5 hours to bring the battery up and then it indicated that it was in float mode. I left it on for another 20 hours and it was still in float mode. The key still wouldn't turn in the ignition. I'm confident that the charger did it's job but I haven't opened up the floor to check out the battery. ???
The engine battery is a substantial battery compared to a regular gas powered auto battery. Diesels need power to start them up. I can't imagine a trickle charger being able to charge a dead battery of that size. Best option is to get the engine battery charged normally at a slow rate. Read the manual about jump starting your battery. Lots of very expensive micro electronics under that hood. In the future I would not use the Mercedes radio while camping and use the entertainment center instead. We hooked up a Sirius unit to the entertainment center and use the camper batteries and solar panels to listen to music etc. Good luck.

Bob
 

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