Very Low Alternator Output
Discussion
I have a 2009 Mercedes Sprinter 311. I've been having issues with the alternator not charging the battery.
My battery light came on, and upon testing the battery with my multimeter, it appeared only 0.5v was getting from the alternator to the battery. On my van, there is a cable that runs from the positive terminal of the battery, to the starter motor where there is a Y junction with a second cable that goes from the starter to the alternator itself. With the cable removed from the alternator, engine off, I'm getting 12.5v from the battery, which suggests that the cable itself is fine, despite being notoriously weak on sprinters.
Next I checked the engine to chassis earth. It was pretty green and corroded at the connections, so I cleaned them up and put on new bolts.
With the cable still removed from the alternator, I started the engine and checked what voltage the alternator was putting out, turns out that number is 0.5v. Can anybody confirm that this is definitely a sign of a dodgy alternator before I fork out for a new one?
My battery light came on, and upon testing the battery with my multimeter, it appeared only 0.5v was getting from the alternator to the battery. On my van, there is a cable that runs from the positive terminal of the battery, to the starter motor where there is a Y junction with a second cable that goes from the starter to the alternator itself. With the cable removed from the alternator, engine off, I'm getting 12.5v from the battery, which suggests that the cable itself is fine, despite being notoriously weak on sprinters.
Next I checked the engine to chassis earth. It was pretty green and corroded at the connections, so I cleaned them up and put on new bolts.
With the cable still removed from the alternator, I started the engine and checked what voltage the alternator was putting out, turns out that number is 0.5v. Can anybody confirm that this is definitely a sign of a dodgy alternator before I fork out for a new one?
Edited by fooby on Saturday 2nd November 15:50
Connect it all back up as it should be & carry out the following.
1. Check the voltage with the engine off.
2. Start the engine & check the voltage at the battery at tick over, also if the battery charge warning light is on/off.
3. Rev the engine moderately to a couple of thousand RPM & check the voltage again, also if the battery charge warning light is on/off.
1. Check the voltage with the engine off.
2. Start the engine & check the voltage at the battery at tick over, also if the battery charge warning light is on/off.
3. Rev the engine moderately to a couple of thousand RPM & check the voltage again, also if the battery charge warning light is on/off.
Thanks for the replies, first thing I did was test battery voltage. 12.6v engine off, fluctuating between 12.7v and 13v running with different revs. I've been reading up on the voltage regulator. Apparently the two prongs can wear out. I need to pick up some female TX sockets as there's a small support bar in the way of the screws. Hopefully this is the issue as it's only a £20 part as against £200 for a new alternator.
I should also add that these tests were performed with a brand new battery. The issue first occurred while driving from Newcastle to Cornwall. After multiple jump starts, running the battery until dead and then attempting to get enough charge into the battery to make it home again I predict that the previous battery is toast.
With a charged battery, the van starts and runs fine. Eventually when the battery is running low on juice, all the dashboard lights and Speedo stop working and it goes into limp mode, eventually cutting out all together. Interestingly, all of the exterior lights turn on once the dashboard shuts down.
Not sure if it's any help, but at first the issue was intermittent. Battery light would come on, but once on the road and up to speed, it would appear to run as normal at around 14v to the battery (battery is under the passenger side floor inside the cab so had a friend test it while driving). After a while though it became a permanent problem.
I should also add that these tests were performed with a brand new battery. The issue first occurred while driving from Newcastle to Cornwall. After multiple jump starts, running the battery until dead and then attempting to get enough charge into the battery to make it home again I predict that the previous battery is toast.
With a charged battery, the van starts and runs fine. Eventually when the battery is running low on juice, all the dashboard lights and Speedo stop working and it goes into limp mode, eventually cutting out all together. Interestingly, all of the exterior lights turn on once the dashboard shuts down.
Not sure if it's any help, but at first the issue was intermittent. Battery light would come on, but once on the road and up to speed, it would appear to run as normal at around 14v to the battery (battery is under the passenger side floor inside the cab so had a friend test it while driving). After a while though it became a permanent problem.
Edited by fooby on Saturday 2nd November 18:00
Sounds very similar to when my w211's alternator was playing up - intermittently the charge would drop off for a few seconds and the dash warning would come up, then go off. A new reg rec with the contacts on the back sorted it, didn't even have to take the alternator off the car, was about £40 for one.
Yep I've fixed a couple of alternators with a new brush pack/voltage reg. Usually about 3 screws to install.
Failing that if you can find a local auto electrical place they should be able to sort it rather than getting a whole new alternator. I had the alternator on my current car completely refurbed (new brushes, bearings, diodes and cleaned) for about £100.
Failing that if you can find a local auto electrical place they should be able to sort it rather than getting a whole new alternator. I had the alternator on my current car completely refurbed (new brushes, bearings, diodes and cleaned) for about £100.
For anyone in the Leicester area I've used these for some years for both alternators & starter motors. Take the old unit in & he'll put it on their test rig while you wait.
Last time was the starter motor on my RRC & the repair was under £20.
https://en-gb.facebook.com/Greens-Starter-Motors-A... (I'm not one of the facebook reviewers)
Last time was the starter motor on my RRC & the repair was under £20.
https://en-gb.facebook.com/Greens-Starter-Motors-A... (I'm not one of the facebook reviewers)
Thank you. Do new alternators usually come with a new voltage regulator? It's integrated with the alternator but is removable on the Sprinter.
It looks like I'll have to remove the alternator in order to gain access to the screws that hold the voltage regulator, so the plan is to get it off tomorrow and check the brushes and commutator for wear. If they look okay, then it seems like it's new alternator time.
It looks like I'll have to remove the alternator in order to gain access to the screws that hold the voltage regulator, so the plan is to get it off tomorrow and check the brushes and commutator for wear. If they look okay, then it seems like it's new alternator time.
Okay, I think I've found the issue. I removed the alternator from the van and removed the voltage regulator. One brush looks fine, the other is practically none existent. Any explanation for the uneven wear? The commutator also looks like it's had it's day so I'll look into rebuilding that with fresh parts.
EDIT: After further inspection, it's not actually uneven wear on the brushes. One of them was jammed in place and sprung back out with some persuasion. Half tempted to put the alt back on and see if this is definitely what was causing the issue before rebuilding.
EDIT: After further inspection, it's not actually uneven wear on the brushes. One of them was jammed in place and sprung back out with some persuasion. Half tempted to put the alt back on and see if this is definitely what was causing the issue before rebuilding.
Edited by fooby on Saturday 9th November 11:56
Solved! Cleaned the brushes up so that they don't jam again, reinstalled alternator and I now have 14.1v at the battery with the engine running. Next step is refurbishing that commutator. I'll replace the brushes at the same time although once unjammed, both brushes are evenly worn with plenty of life left on them.
EDIT: After 10 minutes with engine running, voltage dropped back down to 12.8v and the battery light is back. Definitely know what my issue is now though.
EDIT: After 10 minutes with engine running, voltage dropped back down to 12.8v and the battery light is back. Definitely know what my issue is now though.
Edited by fooby on Saturday 9th November 13:42
Slip-ring looks to be worn away
Should you be able to source a new slip-ring, unsolder worn slip-ring and remove with puller or run a hacksaw blade length ways along it close to the rotor shaft and then break it open and off
Press on new slip-ring, solder, find someone with a lathe and get the slip-ring skimmed. Slip-rings are never central until skimmed
Should you be able to source a new slip-ring, unsolder worn slip-ring and remove with puller or run a hacksaw blade length ways along it close to the rotor shaft and then break it open and off
Press on new slip-ring, solder, find someone with a lathe and get the slip-ring skimmed. Slip-rings are never central until skimmed
I ended up making the most of Euro Car Parts weekend sale and picked up a new alternator for £160 and I get back £55 when I take my old unit in. Sure it's more expensive than refurbishing the old one but tbh I needed the van working ASAP and I have the piece of mind of knowing it's going to be good for years to come.
Battery light is now permanently on but the voltages are all perfect. Went for a 30 minute drive to make sure everything was working as it should which it is. New alternator is a different manufacture so I wonder if the connection that tells the dash light to come on is different. It's a camper and I'm going to install a battery monitor anyway so I can keep an eye on the voltages of the main and leisure battery.
Thanks for all the help.
Battery light is now permanently on but the voltages are all perfect. Went for a 30 minute drive to make sure everything was working as it should which it is. New alternator is a different manufacture so I wonder if the connection that tells the dash light to come on is different. It's a camper and I'm going to install a battery monitor anyway so I can keep an eye on the voltages of the main and leisure battery.
Thanks for all the help.
Edited by fooby on Saturday 9th November 17:53
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