Losing electrical power - alternator or something else?

Last night as I was driving my AC vents started blowing hot air, but there were no other immediate symptoms while driving. I figured it was some kind of electrical gremlin and figured turning the van off and back on would help. So I tried, but it wouldn’t start back up. No crank, just clicks. I measured the battery voltage and it was reading nine volts.

I got a jump from a passerby and limped into a Walmart that was fortuitously just a block away, and bought a new battery. After the new battery was in it started up and I drove another 50 miles without incident, then stopped to sleep and got back on the road this morning. After 25 miles the battery light came on on the dashboard so I decided to head back home, just 100 miles at this point. 25 miles later the battery light went back off but the light for just about every other electrical system came on- ABS, SRS, and a couple others.

I pulled over at a rest stop and checked the battery voltage with the engine running. 8 volts. I turned the engine off and checked again, the battery drifted back up to 10 volts. So it seems clear that the whole electrical system is draining off the battery. Does that mean my alternator has failed, or is there another possible cause, like a fuse somewhere?

I’m hopeful that I’ll be able to make it home by getting a series of jumps to top my battery up enough to go 25 miles at a time or so.

Incidentally this is an RV with a separate battery in the back, the rear electrical system seems fine. However I had in the past had problems with the rear battery not charging while the engine was running so I’m wondering if these problems could be related.

If it’s something other than the alternator, maybe I could find my way to a parts store and do a field repair. If it’s an alternator I think I’d like to get it home before attempting that.


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Obvious the alternator isn't charging the battery!
So is it mechanical or electrical ?
Mechanical.
Is the alternator hanging off or insecure ?
Is the drive belt and the tensioners etc in such poor condition that the belt is slipping on the pulleys?
Is the alternator drive pulley shot and not driving the alternator properly.
Electrical.
Inspect the alternator for wiring attached and not insecure

Big fat one Battery +ve Must be tight and not burnt or charred up.
Smaller field wire at the bottom of the back of the alternator attached ?
This excites the machine to charge and is controlled by the ignition switch through the dash charge warning light.
Remove fuse link cover at the battery +ve connector and inspect the line fuses ! There is a 200 Amp line fuse in plain sight on the left! --is it burnt?

Inspect battery are the connections tight especially the bulkhead grounds!

Still unsure?
Drop into a chain wide autoparts store and have them test your charging system--Its usually free.
Dennis

Jayratch said:

.... I drove another 50 miles without incident, then stopped to sleep and got back on the road this morning. After 25 miles the battery light came on on the dashboard so I decided to head back home, just 100 miles at this point. 25 miles later the battery light went back off but the light for just about every other electrical system came on- ABS, SRS, and a couple others.

....
If it’s an alternator I think I’d like to get it home before attempting that.

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If you don't identify a problem.

Do you have a 120 volt generator to run. That can power a charger while driving.

Simple jump starting at this point will not likely do you any good.

You drove about 100 miles with the new battery. Fully charging the battery with a 120 volt powered charger may get you home. Reduce the use of electrics as much as possible. The cabin fan, A/C clutch, etc. pull a bunch of power.

Good luck.

vic

lindenengineering said:

Is the alternator hanging off or insecure ?
Is the drive belt and the tensioners etc in such poor condition that the belt is slipping on the pulleys?
Is the alternator drive pulley shot and not driving the alternator properly.
Electrical.
Inspect the alternator for wiring attached and not insecure

Big fat one Battery +ve Must be tight and not burnt or charred up.
Smaller field wire at the bottom of the back of the alternator attached ?
This excites the machine to charge and is controlled by the ignition switch through the dash charge warning light.
Remove fuse link cover at the battery +ve connector and inspect the line fuses ! There is a 200 Amp line fuse in plain sight on the left! --is it burnt?

Inspect battery are the connections tight especially the bulkhead grounds!

Click to expand...

Everything I can see looks and feels good, but I don’t know what you mean by “bulkhead grounds.” What is that?





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A bunch of wires seen above the -Ve battery terminal.
Dennis

lindenengineering said:

A bunch of wires seen above the -Ve battery terminal.

Dennis

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When this first began yesterday, I verified the battery and did check all of the battery connections including the ground. It’s good. Wouldn’t the car fail to start if the ground was bad?


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judging from corrosion in the photo, I would hazard to guess a good cleaning of all grounds points is in order. Same for connectors common to alternator. Unplug, squirt electrical contact cleaner and re-plug and un-plug several times while wet with cleaner giving final douche of cleaner prior to final connector attachment. How's the battery post terminals, battery cable terminal crimps? Especially, the ground from battery to vehicle. Detach, clean reattach.

Jayratch said:

When this first began yesterday, I verified the battery and did check all of the battery connections including the ground. It’s good. Wouldn’t the car fail to start if the ground was bad?


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I guess this is what I’m getting at: if I can be reasonably certain it’s the alternator, I’ll just find a way to limp it home (I’ve got a friend coming to charge me up, and I figure we should be able to get 20-30 miles at a time that way and make it home in one or two stops) and then order an alternator and do the swap in my own driveway.

If it’s much more complicated than that I’ll probably have to take it to a shop for repair, and I’m dreading having to do that since I haven’t found a good shop in my area yet. Apparently a lot of places don’t work on these at all. Mercedes does but their labor rate is obscene and parts are significantly marked up compared to online. I took it to another fleet/RV shop to get an inspection and I think they tried to cheat me - wouldn’t pass it without two repairs that other shops said were unnecessary, and their price for those jobs was about 50% higher than I think it should’ve been. I think they may have overcharged me for the other work I asked them for too ($700 to remove TV antenna and awning so I could get a roof rack on).

So I’m really hoping it’s something I can do myself so it doesn’t end up being another $1000 to a shop I don’t trust. But if it’s not the alternator I’ll have wasted $200 replacing a good part.

Are alternators a wear/consumable part? Should I just go ahead and order the replacement on the theory that I might eventually need one anyway?


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Jayratch said:

When this first began yesterday, I verified the battery and did check all of the battery connections including the ground. It’s good. Wouldn’t the car fail to start if the ground was bad?
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How did you check, visually or actually detach and clean?

I'll bet a weeks pay it's a bad ground.

Jayratch said:

...

Are alternators a wear/consumable part?
...

Click to expand...

100% ... eventually.

Jayratch said:

... Should I just go ahead and order the replacement on the theory that I might eventually need one anyway?


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http://europarts-sd.com/item.asp?cID=101&PID=2604

https://sprinter-source.com/forum/showthread.php?t=18432

Amazon often lists them. Personally I would stick to Bosch brand... maybe Valeo.

vic

There are tests that determine if the alternator and related components are functioning. Don't blindly throw parts at it.

Not a Sprinter specific but informational nontheless. Explore YouTube for more information. The guys accent is awesome. Buttery = Battery LOL.

https://m.youtube.com/watch?v=qViKXzQhaqA

Bobnoxious said:

There are tests that determine if the alternator and related components are functioning. Don't blindly throw parts at it.

Not a Sprinter specific but informational nontheless. Explore YouTube for more information. The guys accent is awesome. Buttery = Battery LOL.

https://m.youtube.com/watch?v=qViKXzQhaqA

Click to expand...

I did try that test. I have a little bit of mechanical and electrical knowledge, just maybe not enough. I tested the voltage across the battery terminals with the engine running and with it off... it was actually lower with it running than off. Of course idiotically I noticed that right after the first jump start but still ignored the signs and tried replacing the battery.

Another check I did was verifying that the voltage across the alternator was the same as the voltage across the battery (although for obvious safety reasons I didn’t attempt this check with the engine running). This to me suggested that the wiring including the ground was good.

I guess what I’m not getting about a bad ground is, how could the ground be good enough for the car to run off the battery but not good enough for the alternator to charge the battery?



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Bobnoxious said:

How did you check, visually or actually detach and clean?

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I visually checked and detached it from the battery end. I hadn’t yet tried detaching it from the body side. I’ll try that next I guess although admittedly I’m skeptical that the connection could simultaneously be good enough to power the car off the battery but not good enough to charge the battery. Just doesn’t match up with Kerchhoff’s voltage law. Unless somehow the ground connection itself is dropping a few volts? But that doesn’t make sense to me either, because if that was the case then the rest of the car would exhibit low-voltage behavior even before running for a while.


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With the engine running measure the voltage between the battery NEGATIVE terminal and a good clean ground directly on the engine. Try to connect directly to the lead terminal of the battery rather than the bolted on terminal.

If your Voltage measurement is below 0.1 V then this indicates your engine ground connection is OK.

If you are seeing anywhere near 2.0 V then you have a serious ground fault.

Keith.

Cheyenne said:

With the engine running measure the voltage between the battery NEGATIVE terminal and a good clean ground directly on the engine. Try to connect directly to the lead terminal of the battery rather than the bolted on terminal.



If your Voltage measurement is below 0.1 V then this indicates your engine ground connection is OK.



If you are seeing anywhere near 2.0 V then you have a serious ground fault.



Keith.

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Oh... I did do that. Zero volts, 12 ohms resistance from negative battery post to a bolt on the radiator bracket.


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When you discover the solution, please post for the forum collective?

Aqua Puttana said:

Amazon often lists them. Personally I would stick to Bosch brand... maybe Valeo.



vic

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Yeah, it’s $183 on Amazon, with Prime so free fast shipping. I talked to a mechanic who said it’s the most likely problem based on the pattern of symptoms. I think I’ll just go ahead and order it.



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Bobnoxious said:

When you discover the solution, please post for the forum collective?

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Yes Bob, I will. I’m going to go ahead and order the part now. Sadly it’s not going to be feasible to get back on the road today so the weekend is a bit of a bust, might still head out in the car for a shorter trip or just work Monday and take Friday off instead. Hopefully it arrives in time for me to do the swap on Thursday. I’m embarrassed to admit I haven’t done even a job this big myself in probably ten years so I guess I’m looking forward to it, back pain aside. In my defense I was in a fairly serious accident seven weeks ago and I’m still not fully recovered so I’m dreading the inevitable pain.


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Jayratch said:

Yes Bob, I will. I’m going to go ahead and order the part now. Sadly it’s not going to be feasible to get back on the road today so the weekend is a bit of a bust, might still head out in the car for a shorter trip or just work Monday and take Friday off instead. Hopefully it arrives in time for me to do the swap on Thursday. I’m embarrassed to admit I haven’t done even a job this big myself in probably ten years so I guess I’m looking forward to it, back pain aside. In my defense I was in a fairly serious accident seven weeks ago and I’m still not fully recovered so I’m dreading the inevitable pain.
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I dunno brother, you certainly don't want to aggravate your injuries. Do you have a friend that can help? Good luck. Bummed I couldn't be more helpful.