View Full Version : Dying battery, dying alternator, or something else?

05-26-2015, 02:09 AM
Hi All,

I'm not particularly good at diagnosing electrical problems. Before I start replacing components at random, I thought I'd ask for opinions here.

I've got a 2005 Sprinter that I bought two years ago. No idea about the history of the battery, except that it is more than two years old. Then van has always struggled to start in temperatures below 10F, though it starts just fine when I jump it. So my assumption is that the battery is not up to the task.

Today, after driving for several hours at highway speeds in moderately warm conditions (approx 80F) my UltraGauge sounded a low voltage alarm. It was reporting an ECM voltage of around 11.7V to 12V. Normally the UltraGauge reports around 13.5V.

I have no problem replacing the battery and going from there, but if this is obviously the symptom of a failing alternator, I suppose I ought to replace that too.

BTW, I read through the battery recommendation thread here. Since I care mostly about cold weather starting, I was thinking a regular lead acid battery, not AGM. Correct?


05-26-2015, 03:22 AM
If you want to avoid ready, fire, aim, fully charge the battery and load test it. If you can't do a "proper" load test, fully charge it, let it sit several hours and check the standing voltage. It should be +12.6 or 12.7 after sitting several hours. Then turn the headlight on for a few minutes, check the standing voltage, and then once again check it after sitting for a couple of hours. The voltge will drop after the headlights have been on for a while, but should recover most of it after a couple of hours.

Once you have a fully charged battery, if you start the van, the voltage from the alternator should be about 14vdc or maybe a bit higher.

Bottom line, it is touch to properly test an alternator if your battery has not been properly tested and found good.


05-26-2015, 04:36 AM


Tooth Fairy
05-26-2015, 09:15 AM
Just go and buy a new battery, its not like they cost your first born child to get one. :thinking:

05-26-2015, 03:23 PM
Or, simply "borrow" another battery from another vehicle. It doens't have to be the exactly the same battery size, shape and capacity for a simple test.


05-26-2015, 03:55 PM
So, you know battery is over 2 years old? Buy battery and see how it goes.
Our original battery was still going at 6 1/2 years but dealership said they had " great sale" going and battery was getting old. That great sale battery lasted less than 2 years. Seemed to be getting slow to start and we had about month freezing temps with snow/ice. Last battery been in since Feb 2012 got it at and installed at Sears. Still going pretty good but figure will replace before next winter if still have van. We have Ricon wheelchair lift and have been really happy with lengths of time batteries have lasted and just always used just flooded lead acid standard batteries.
Our powerchairs have had no maintaince sealed lead acid, AGM and Gel batteries, can't see putting that money in battery for van. Besides they do good to last 2 to 3 years in powerchair.
Now if you are using secondary battery in van then yea, pick up AGM for that purpose. But, be sure to keep it charged and drain it down a good bit every once in a while. The "new" style powerchair chargers these days have 'feature' that suppose to keep battery cleaner inside and make them longer lived. Think mostly just help explain why makers with to off-board charger instead of built in chair style that powerchairs came with for several years.
"Good Luck!"

05-26-2015, 03:59 PM
If alternator output is below spec, it's most certainly alternator related. That does not eliminate your battery as a problem as well but if you have low/little voltage off the alternator, you need to diagnose and solve that problem, or you'll just start killing batteries.

My 2005 was eating alternators back in January. I can relate to how fun it is to troubleshoot. :/ Having the gauge is really useful, by the time the low-voltage light list up on the dash, the van was losing power and about to die.

Check to make sure you're turbo resonator is not failing. I killed 2 alternators before I figure out the resonator was likely blowing them out (literally). And since the dang resonator has to come off to swap the alternator, might as well replace it at the same time, it's about a $20 part.





05-26-2015, 06:30 PM
my alternator failed last winter on the way home one night. The van stopped charging and the light would come on for a mile and half and the headlights would flicker bright and dim...then the alternator would charge for half a mile and then not. I made it home and ordered a new alternator. The alternator is relatively easy to change....however if you have trouble starting I would have the battery tested and likely replaced first. Once you have a healthy battery and clean terminals then I would start the van and measure the voltage across the battery while the van runs. You should see between 13v and 14.4v. If you see this voltage then your alternator is ok. If you have had the van for a long time and it has the original alternator you might consider ordering a spare to keep in the van. a brand new not rebuilt 120 amp alternator will run you about $260 but if you have one on hand it might save you an expensive repair in the middle of nowhere.

05-26-2015, 07:24 PM
Thanks for all the suggestions. The date stamp on the existing battery isn't very clear, but if I'm reading it correctly, then the battery is six years old. So I'm definitely replacing the battery. At that point I'll check the voltage from the alternator (which is probably original) and if it seems low I'll replace that and the turbo resonator while I'm at it.

Anything else that I should replace when/if I do the alternator? Serpentine belt seems an obvious choice. I seem to recall something about a harmonic balancer, but I'm not finding the right keywords for a search on that one.

Thanks again!

05-27-2015, 04:04 PM
I put in the aluminum pipe that replaces the resonator. I have not noticed any issues with noise and it cannot blow apart like the resonator. It costs about 3 times as much as a resonator but wont leave me in limp home on a trip due to a low boost signal.

05-27-2015, 04:24 PM
I put in the aluminum pipe that replaces the resonator. I have not noticed any issues with noise and it cannot blow apart like the resonator. It costs about 3 times as much as a resonator but wont leave me in limp home on a trip due to a low boost signal.

I've got that update on my to-do for later this summer. There is enough noise from under the hood that a little turbo whine/noise is not going to be a big issue for me. :)