Weird charging problem

Scrufdog

New member
2007 Sprinter, build date 10/07. Chassis Cab setup with box on back. Diesel.

It first started a week ago. Started the van, battery stayed on until I revved the engine. Happened again yesterday. Today while driving the battery light came on, then the seat belt light came on... I always where my seat belt. Started looking like Christmas on the dash, both lights alternating back and forth, then nothing for a bit, then flashing lights randomly. I got out my voltage meter and hooked it up. While driving normally system voltage is at 13.3vDC. When either the seat belt or battery light turns on, drops to battery voltage, 12.8 - 12.0 depending on how long it hasnt been charging.

Sometimes the seat belt light comes on, nothing charging, then goes off, starts charging again. Sometimes the battery light comes on, stops charging, then it always turns off, then the seat belt light turns on, still not charging, then if the belt light turns off it will start charging again. The battery light never just turns off, it always switches to the seat belt light first. I've noticed I can pretty much always get it to stop charging under heavy acceleration, although it will randomly stop charging while cruising or decelerating. If I'm idling no amount of fast or slow revving will make the light come on. Seat belt on or off doesnt effect the situation. I can hear what sounds like a relay clecking under the dash as charging kicks in and out.

Normally I'd just go for the alternator, but seems odd that the seat belt light is 'involved' in the problem. Just for kicks I checked most of the reachable connections under the hood, everything was dry and properly seated. I'm wondering what the relay has to do with anything. I have no wiring diagrams to look over at the moment.


Whatcha think?
 

piper1

Resident Oil Nerd.
See this thread for pics

https://sprinter-source.com/forums/showthread.php?t=13606

13.3 v is not normal charging, 12 v is no charging. If the big cable is not letting charging current through, it may find ways out through the other alternator wires...which are ECM controlled wires. Wanna guess what happens when those itty bitty wires try to take some of the alternator output? It doesn't end well.

The cables are a problem..it is an easy first check before you (or worse you have to pay someone) to go on an electrical fishing expedition.
 

Altered Sprinter

Happy Little Vegemite
14.4 v is full charging 12v what ever,it is still charging and that's where a load is implied of X+= 12.8 to 12v is a large draw for voltage... safety belt is an ecu issue. "With voltage signal settings".
The ecu is simple to rectify but You require star diagnostics to to reset the values, as piper states cables! look at your starter cables for corrosion, then trace back to starter battery for visible rubbing, that may be earthing off metal for a power spike.???
Safety belt usually is associated with heated seats if this is a ECU DAS fault for coding..No it will not show on your dashboard fault codes either.
If you have changed batteries they may not be compatible to your original ecu voltage settings for your alternator.
Richard
 

Scrufdog

New member
It was the cable. Burnt out at the Y connection. Best part of all, after replaceing it, the alternator charged for about 20 seconds, then died completely. Replaced it and everything is fine. Apparently the alternator was really struggling with the bad connection screwing it up.

thanks for the help
 

Eric Experience

Well-known member
Scrufdog.
Just for your peace of mind, The seat belt light comes on for a set time after the D+ relay closes, the D+ relay closes when the alternater gets up to voltage, so what you were seeing is normal for an intermitant charging problem. Eric.
 

Aqua Puttana

Poly - Thread Finder
Without a good connection for the battery to act as a buffer and keep the voltage down your alternator may have been spiking up the voltage. That MAY have caused the regulator to burn out. An alternator shop can check that for you. You may be able to just replace the regulator and have a spare alternator for a reasonable price. FWIW. vic
It was the cable. Burnt out at the Y connection. Best part of all, after replaceing it, the alternator charged for about 20 seconds, then died completely. Replaced it and everything is fine. Apparently the alternator was really struggling with the bad connection screwing it up.

thanks for the help
 

Scrufdog

New member
yeah, I figured thats what was going on with the seat belt light. I wasnt sure if the relay i was hearing activated the alternator, or reacted to it.

I'm gonna have the alternator rebuilt and keep it as a spare for sure.
 

BBBayud

New member
So glad I found this thread. My wife and I just bought a Pleasure Way Plateau RV on a 2007 Sprinter 2500 Diesel chassis a few days ago and the exact same problem occurred. We didn't have any problems on our 700+ mile drive back to our home, however after sitting a day or two we took it for a drive and the battery light came on a mile from home and then the problem alternated between the battery light and seat belt light coming on with the associated relay clicking noted above. I checked the wiring yesterday but not able to find a smoking gun, so looking at just replacing it and hoping the problem ends there.
 
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bcislander

'07 Mercedes-badged Dodge
The original Y-Cable in 2007-2010(?) Sprinters was poorly designed and prone to failure.

Check the system voltage with the engine running. The voltage should be ~14.0V to 14.2V.
A low system voltage can cause multiple fault codes as well as resulting in a battery that is never fully charged.
A voltage below 14.0V usually indicates a faulty Y-Cable and/or engine to chassis ground strap.

Replace the Y-Cable and/or ground strap if the system voltage is below ~14.0V.

A few relevant Y-Cable search results:



 

BBBayud

New member
Thank you!

Update 8/27/20: I checked the main and cabin batteries and both read over 12.5V. I then started the RV and the main battery dropped a little and stayed about 12.2V. All the initial checks on the dash cleared. About 20 seconds passed and then a few beeps sounded with the seat belt sign coming on; they stopped soon after and then the main voltage went up above 14V. While idling the voltage started to bounce primarily between 13.5V and 14.2V (it went as low as 12.9V a few times). I pushed on the accelerator to keep revs over 1000 RPM and the measured voltage went and stayed above 14V. The battery light on the dash never came on, and the random seat belt light on/off with the relay sounds didn't occur either. Going to take it on a test drive a little later. The Forum consensus seems to be that I should change out the Y cable for good measure, but based on the results, I'm not sure what's going on. Thanks again.
 
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autostaretx

Erratic Member
Your belt could be slipping (check tensioner), the alternator's pulley clutch could be acting strangely

--dick
 

TechHandyman

New member
Just went through this exact same situation and solved it after 2 months. Dealer changed the alternator before delivery because it was charging “low.” Ended up being a bad alternator, and putting an OEM in from Dodge (they were cheaper than MB), solved the issue. Before the alternator, I changed the Y cable and belt tensioner, as well as put in a new chassis battery and ground strap. Alternator and Y seemed to be the issue though.
 

BBBayud

New member
Thanks everyone for your comments - very helpful. I took a couple short drives over the weekend, the battery light came on and stayed on for longer periods with the seat belt light coming on a few times when the battery light went out (but soon back on) I couldn't get the alternator to put out 14V at the battery when I checked it today. As the RV has 139K on it, I will probably be going the route of changing out a few things not knowing if they've ever been changed in the past. The trips we'll be taking will be well over 1K miles from home, so don't want any problems tied to what I could have taken care of. Thanks again.
 

BBBayud

New member
In my younger days I liked working on cars and had no problem replacing a clutch on my Camaro, setting the timing, or changing out a water pump or alternator. Now retired, I want to leave that to younger folks but got my first taste of what that will mean after my first trip to Mercedes to look at my RV. I wasn't surprised necessarily that they wanted about $731 to replace the alternator (I knew Mercedes would be expensive), but surprised that price was for a remanufactured one. I've read quite a few threads on remanufactured alternators and they seem to be hit or miss, and have less life overall. Other problems they noted - leaking throttle valve seals ($1,005), #2 glow plug ($316), and turbine silencer on its way out ($417). I asked about the Y cable and they said it was fine. No work has been authorized yet, I'm still thinking on it.
 

bcislander

'07 Mercedes-badged Dodge
In my younger days I liked working on cars and had no problem replacing a clutch on my Camaro, setting the timing, or changing out a water pump or alternator. Now retired, I want to leave that to younger folks but got my first taste of what that will mean after my first trip to Mercedes to look at my RV. I wasn't surprised necessarily that they wanted about $731 to replace the alternator (I knew Mercedes would be expensive), but surprised that price was for a remanufactured one. I've read quite a few threads on remanufactured alternators and they seem to be hit or miss, and have less life overall. Other problems they noted - leaking throttle valve seals ($1,005), #2 glow plug ($316), and turbine silencer on its way out ($417). I asked about the Y cable and they said it was fine. No work has been authorized yet, I'm still thinking on it.
FWIW, I would replace the Y-Cable before replacing the alternator.
 

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