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View Full Version : Time to replace alternator?


A.Hayes
08-19-2013, 06:05 PM
Hi all,

I've noticed lately on my Ultragauge that while driving my voltage is around 13-13.5v, and dips down to 12.75v or so with the AC on. I'm wondering if this is an actionable level for alternator replacement, which as far as I know is original ('02). The battery is also getting older at 5.5 years, but load tested good a few months back, and is still around 12.4v cold.
Anyway, I've read other threads suggesting that 14v+ is more normal operating (alternator) voltage.
We are hitting the road for a week on Friday and would prefer to avoid problems if those numbers are out of normal range.

Thanks for any input.

cahaak
08-19-2013, 09:08 PM
While driving, my voltage reads around 13.6, that was with the AC off, I will remember to check it with the AC on.

Chris

autostaretx
08-19-2013, 09:57 PM
What current rating is your alternator?

There will be times when the AC is starting its fans (etc), and it'll draw more than its usual current.
If (for example) you only had a 90 amp alternator, it's possible that the combined electrical load of the Sprinter is approaching that.
Therefore it's perfectly reasonable for the voltage to sag (the regulator is going to kick in and limit the alternator's current to avoid damage).

If they're on, try turning off the headlamps, or dropping the fan speed to 1, killing the shake-the-neighbors stereo, etc etc
and see if the voltage pops back up.

If could even be a loose belt being willing to let the alternator slip...

--dick

pfflyer
08-19-2013, 10:42 PM
If could even be a loose belt being willing to let the alternator slip...

--dick[/QUOTE]

Could it also be the tensioner? If it could and turns out to be I recommend the oem tensioner. I should have done this and replace the alternator (Bosch) at the same time on my 02. I had over 400k at the time and don't know if they were original or not. It would have saved me one towing bill. Change the idlers as well they are cheap compared to the others. How many miles on yours?

NelsonSprinter
08-20-2013, 12:07 AM
The clutch on my '02 alternator seized and snapped my tensioner off it's bolts so I replaced the whole alternator and had to drill out the old bolts and re-tap, meaning the rads and front end had to be removed to access them. Luckily the van runs for 30 minutes after alternator is de-belted if it's cool enough.
ie I wish I had replaced my alternator earlier than I did, not known what the voltage was.

A.Hayes
08-21-2013, 05:17 AM
Thanks everyone for the responses.

I'm wondering now if I just have a battery on the way out- Testing today after sitting overnight it was just under 12.2v; turning on the headlights got it down to 11.9v or so. No starting problems yet though.
Once running, with all accessories OFF, it was hovering around 13v at idle on the Ultragauge.

So, would a failing battery read low while being charged by a fully functioning alternator? The battery is 5.5 years old, and I'll likely replace it soon anyway.

As far as the belt slipping, I'll double check that tomorrow. After a couple of thrown/shredded belts a few years back, I'm pretty sure Upscale put on new idler pulleys and tensioner, and all else has seemed fine there for the last 20-30K mi (btw van has 151,000mi now). NelsonSprinter's cautionary tale did not fall on deaf ears though...

Off the load test the battery again tomorrow. Thanks again!

autostaretx
08-21-2013, 02:41 PM
I'm wondering now if I just have a battery on the way out- Testing today after sitting overnight it was just under 12.2v; turning on the headlights got it down to 11.9v or so. No starting problems yet though.
Once running, with all accessories OFF, it was hovering around 13v at idle on the Ultragauge.

So, would a failing battery read low while being charged by a fully functioning alternator? The battery is 5.5 years old, and I'll likely replace it soon anyway.
... or would a failing underperforming alternator be allowing your battery to be run low?

Many people consider 5 years to be a battery's expected life, and replace them based upon the calendar. Mine's now 8 years old (based upon vehicle delivery date to dealer), and (especially after one bonehead let-it-get-flattened incident by me 2 years ago) now only holds 12.5 volts long-term. But the Sprinter gets it up to 14.2 v immediately after starting, and the long-term on-road charge level is in the 13.5 to 13.7 range.

I would consider a 0.3v drop due to the headlights a little excessive (0.2 would be better).
Give the battery a full plug-in-the-wall charge, let it sit overnight, and then measure/test it.
If it's above 12.6v after a real full charge, then it's OK.
If it still settles back down to 12.2v, then it's toast.
Your dips could be intermittent internal cell-shorting.

Or.. you could replace the battery (are the cells full?) and be happy.
If the voltage dips cease with the new battery, that would indicate you've fixed it.
After about a month, check it again. If it's down to 12.2v, then it was the alternator (which includes the belts).

--dick

Aqua Puttana
08-21-2013, 06:05 PM
Some things I've noticed.


My experience is that as a battery gets a bit weak the charge voltage seems to jump to a bit above 14 volts by the gauge for a shorter time (tapers off quicker) than when a battery is strong. If your voltage is going up to high 13 or low 14 and then tapering off quickly I would have the battery load tested. Of course poor connections heating up can also reduce the gauge voltage.

As our Sprinters age there seem to be more problems tracing to bad cables or poor connections. The ground strap seems to come up more often lately.

Certainly test for operation of the alternator, but don't just focus on the alternator only. You are dealing with a system. vic

A.Hayes
08-22-2013, 09:31 PM
An update:
I went to a local battery shop yesterday and had them load test the battery and alternator. They said both were fine. Unconvinced, and figuring there was maybe some Sprinter specific oddity going on, I called Upscale and was able to get it in this morning. They also tested the battery as good (12.67v, measured 923CCA, rating 850CCA) Starter test was normal at 10.9v, and alternator tested at 13.56v. They also checked all grounds and found no issues.
They said that voltage is regulated by the ECM, and that several years back they saw another van with similar lower than normal voltage readings that did not change with an alternator replacement. So, it seems that my ECM is setting the voltage a bit low for some reason, but all other parts of the system are operating normally:hmmm:. I'll keep on Sprintering and post if anything else develops...

Aqua Puttana
08-22-2013, 10:01 PM
Hi all,

I've noticed lately on ...

Thanks for any input.
You still get full credit for awareness and noticing the change, if that's worth anything.

An update:

...They said that voltage is regulated by the ECM,
The alternator voltage regulator is integral to the unit :idunno:, but the voltage excitation originates (if memory serves) from the IC Instrument Cluster. So the ECM may have final say. Some detail is here if anyone is interested.

http://sprinter-source.com/forum/showthread.php?p=206402#post206402

and that several years back they saw another van with similar lower than normal voltage readings that did not change with an alternator replacement. So, it seems that my ECM is setting the voltage a bit low for some reason, but all other parts of the system are operating normally:hmmm:. I'll keep on Sprintering and post if anything else develops...
Can't argue with experience. As long as you have no real problems, I would also just drive on as you said.

Thanks for the update. vic

LuckyDawgz Jim
08-26-2013, 03:19 PM
FYI even if you may not need one just yet, if you can afford a spare, here is a complete new 150amp Bosch for under $200 delivered.

http://www.amazon.com/gp/product/B000BZII30

autostaretx
08-26-2013, 04:22 PM
if you can afford a spare, here is a complete new 150amp Bosch for under $200 delivered.
But, as he said (and was told by Upscale), it may "simply" be a case of the ECM (in cahoots with the IC) not telling the alternator to provide enough power... the alternator may be willing, but if the Boss says "loaf", it'll loaf.

What can ya do?
(a) monitor the IC-to-alternator line... see at what battery voltage levels it's kicking in and out ("charge!" vs "loaf")
(a1) compare to a "known good" Sprinter.
(b) if memory serves, Vic doesn't have the training manual for this sub-system... so we're stuck with the minimal description in the service manual. The ECM could be *telling* the IC to assert the charge signal, or the IC's smarts could be doing it on their own.
(c) one could (carefully) try intervening: assert a manual "charge!" signal, see if that helps.
(this would first require doing (a) with an oscilloscope to catch things like PWM effects (if any) and sane voltage levels.)
It's even possible that the "charge!" signal is analog: with the level controlling the alternator's field current.

Non of the subsidiary diagnostic-tree manuals that come with the Service Manual cover the charging system, so we're left to our own foggy brains for deeper diagnoses. Drat.

--dick

seans
08-28-2013, 04:13 AM
But, as he said (and was told by Upscale), it may "simply" be a case of the ECM (in cahoots with the IC) not telling the alternator to provide enough power... the alternator may be willing, but if the Boss says "loaf", it'll loaf.

What can ya do?
(a) monitor the IC-to-alternator line... see at what battery voltage levels it's kicking in and out ("charge!" vs "loaf")
(a1) compare to a "known good" Sprinter.
(b) if memory serves, Vic doesn't have the training manual for this sub-system... so we're stuck with the minimal description in the service manual. The ECM could be *telling* the IC to assert the charge signal, or the IC's smarts could be doing it on their own.
(c) one could (carefully) try intervening: assert a manual "charge!" signal, see if that helps.
(this would first require doing (a) with an oscilloscope to catch things like PWM effects (if any) and sane voltage levels.)
It's even possible that the "charge!" signal is analog: with the level controlling the alternator's field current.

Non of the subsidiary diagnostic-tree manuals that come with the Service Manual cover the charging system, so we're left to our own foggy brains for deeper diagnoses. Drat.

--dick

I was under the impression from the manual that the small wire from the alternator to the instrument cluster was only an input to the IC indicating whether or not the alternator was providing current. In the '06 manual it is called the "generator monitor signal".

If an oscilloscope shows no obvious digital control signal, then a diode (assuming not a lot of current is flowing) and maybe a pulldown resistor could help confirm this either way. My van is down at the moment so I'm unable to check.

A.Hayes
08-31-2013, 09:13 PM
Thanks for the responses and info... alas, I don't have an oscilloscope, and wouldn't know what to do with one anyway without further reading.

Anyway, my van has continued to run perfectly normally, and other than the lower than "normal" voltage readings on the Ultragauge, I would have no idea of any issues with the charging system and controls (wherever they live!). Just spent a week camping on the S. Oregon coast and it ran flawlessly the whole time- no slow cranks or other oddities.

Of interest is that I have noticed that while typical running voltage remains around 13V (+ or - .5V, depending on accessories, etc), after isolated starts it'll be at 14.1V or so, and remain around that or maybe come off just a bit for the duration of the run cycle, until shut off again. Then next start it's back closer to 13V... no obvious related pattern of hot or cold starts, etc. Maybe there is a loose connection somewhere that is intermittently operating normally??

I'll keep an eye on it and post with any changes.

seans
08-31-2013, 10:07 PM
Of interest is that I have noticed that while typical running voltage remains around 13V (+ or - .5V, depending on accessories, etc), after isolated starts it'll be at 14.1V or so, and remain around that or maybe come off just a bit for the duration of the run cycle, until shut off again. Then next start it's back closer to 13V... no obvious related pattern of hot or cold starts, etc.

Honestly, my van does the same thing. I can guess but I don't know why. Maybe someday someone will put a voltage regulator on a test bench and chart current, voltage, temperature, and operating time.

A.Hayes
08-15-2014, 05:08 AM
Old thread update...
I got a new alternator (150 amp installed at a reputable shop) a few months back after seeing more drop in running voltages, down into the mid 12s or so. No starting or running issues at all, but I'm still seeing similar lower than expected voltages on the Ultragauge. I have seen as low as 12.2 and average maybe 12.75. It is NOT really affected by how many electrical components I have running- AC, radio, etc.
So, today I took it by a battery shop since my battery is 6.5 years old. It was a bit weak, but the strange part is that the tech was reading 12.85 running voltage at the battery and 14.1 when measured right at the alternator. So any ideas about what is causing the voltage drop? Isn't it just a single big cable running from the alternator straight to the battery? This is out of my area of expertise, so I'm inclined to take it back to the auto electrician and have it chased out before more problems develop. Is there anything Sprinter specific to these components that I/he should know about?
As always, thanks for any input!

Aqua Puttana
08-15-2014, 01:00 PM
It doesn't need to be a Wye cable, even a single cable has connections at each end which can deteriorate. Your comments now point to connection issues.

I believe that Showkey and Autostaretx have both outlined cable testing procedures using a multimeter or simple voltmeter. An advanced search using voltage drop as key word and either member name should get you the info.

As I mentioned here earlier. You are dealing with a system.

Some things I've noticed.


My experience is that as a battery gets a bit weak the charge voltage seems to jump to a bit above 14 volts by the gauge for a shorter time (tapers off quicker) than when a battery is strong. If your voltage is going up to high 13 or low 14 and then tapering off quickly I would have the battery load tested. Of course poor connections heating up can also reduce the gauge voltage.

As our Sprinters age there seem to be more problems tracing to bad cables or poor connections. The ground strap seems to come up more often lately.

Certainly test for operation of the alternator, but don't just focus on the alternator only. You are dealing with a system. vic

vic

A.Hayes
09-04-2014, 10:12 PM
Your comments now point to connection issues.


vic

SOLVED... Vic nailed it.

Work/life/etc finally slowed down enough for me to do a little poking around. I used a DVM and jumper cables to pin down bad ground connections at the firewall and engine ground strap below the fuel filter. Took off both (at the chassis end only), cleaned with electrical contact cleaner and a high grit sandpaper, and re-assembled. Running voltages at the battery now match what I get testing voltage from the alternator to engine block.

I never did have issues with the van running, but the voltage measured on the Ultragauge continued to drop over the last year or so down to the mid 12s. Sooner or later I think I would have had the dreaded "Start Error" or other issues. Now it's around 14V all the time.

So it's probably not a bad idea to check running voltage occasionally (esp if you do not have a UG/Scangauge/etc giving you real time data) to see if there is significant voltage drop. It's a quick and easy fix, even for those like me with caveman level mechanic skills...

Thanks again to everyone who jumped in:thumbup: