Vito 2.1 109cdi Battery warning light. Alternator test/ removal?

[Alans dad]

Red battery warning light came on. I drove it to Birmingham from London like that and had a bit of trouble starting it for return journey but once it started it drove home to London. When I tried to start the van the next day the battery was weak and sluggish at starting but it did start. I drove it 5 miles and then the engine stopped while I was driving. There was no electrics at all. No hazard lights nothing on dash board. Like the battery was disconnected. Couldn't start it so called recovery and they towed it home. They didn't test anything or try jump start as car was in precarious place on duel carriageway. Battery was flat. I thought it was the battery at fault but now I think it is the alternator.
Removed battery and charged it for 24 hours. Measured voltage on disconnected battery 12.6 V. then used a battery test meter under load and the reading said the battery was OK. I charged it up again and put battery back in van and started engine no problem. I followed advice to disconnect earth lead from battery with engine running to test alternator. Did this and engine stopped immediately .
The battery is housed under the passenger seat and slides in through small opening from the side when the passenger door is open. I can't get to the live terminal when the battery is in place. However, there are two points under the bonnet where I can jump start from. One is an earth stud coming out of the body and the other is a live stud in the fuse box. Should I take a voltage test from these points to test alternator? I presume they are just extensions from the battery terminals.
I think my alternator has a fault and so if I am going to try and remove it for fixing or replacing. Can anyone give me advice on how to remove it. It seems very inaccessible.

 

[mattkh]

..... I followed advice to disconnect earth lead from battery with engine running to test alternator.

I never do this.

 

[M80]

I think there is still a fair chance it's your battery.
12.6 after a charge isn't a good result, but I've had batteries as low as 11.8 still running the vehicle ok. Although then spurious alarms are likely.

Yes test voltage at the jump points. You should see the voltage rise to 14.3 - 14.7 volts, 14.7 on yours. with a healthy alternator. But a duff battery can bring that down.
I can't remember the sequence to bring it up but voltage can be monitored on your dash.

I use a plug in volt meter in the ciggy lighter, although as cheapo's they can be inaccurate but still reasonable to monitor trend.

 

[Alans dad]

I never do this.

I thought it sounded a bit dodgy but the advice seemed to make some sense when it was explained like this : The battery is needed to start the engine then the alternator supplies the electricity to keep the engine running, any electrics in use and to keep the battery charged up. The theory was if the battery was disconnected while the engine was running then as long as the alternator was working, the engine would keep running.
My knowledge is very limited and so I am easily led by anyone who seems to know what they are talking about. I've used my phone a friend option so now I am asking the audience. Still have my 50/50 option.

 

[Alans dad]

Yes test voltage at the jump points. You should see the voltage rise to 14.3 - 14.7 volts, 14.7 on yours

I will do this.

 

[EmilysDad]

I thought it sounded a bit dodgy but the advice seemed to make some sense when it was explained like this : The battery is needed to start the engine then the alternator supplies the electricity to keep the engine running, any electrics in use and to keep the battery charged up. The theory was if the battery was disconnected while the engine was running then as long as the alternator was working, the engine would keep running.
My knowledge is very limited and so I am easily led by anyone who seems to know what they are talking about. I've used my phone a friend option so now I am asking the audience. Still have my 50/50 option.

I've seen that kind of thing done years ago, swapping batteries of a running car and turning lights etc on to give the alternator a load while the battery is removed. But that was before cars were as complicated as they are now and as Matt says, I'd not consider it on a modern car.

 

[Staunch]

No don’t do that.. check voltage at the battery with loads off. 14.2 volts to 14.5 volts (I’d only panic if it said 15.0 volts but you can get this on smart charge systems.)

move the earth from battery to a suitable earth on the body then on the engine. Any large difference is a dirty/loose earth.

repeat with loads on. I.e. cabin fan, main beam, fogs but nothing that will alternate like wipers or hazards.

check the voltage at the back of the alt from underneath. Should be the same as at battery or slightly more. If significantly more there is a problem with the cable to the battery.

If you were stuck in a desert with no option then put a jump pack on the jump points, and then change your battery. But the location makes this tricky as everything will be live.

 

[M80]

I thought it sounded a bit dodgy but the advice seemed to make some sense when it was explained like this : The battery is needed to start the engine then the alternator supplies the electricity to keep the engine running, any electrics in use and to keep the battery charged up. The theory was if the battery was disconnected while the engine was running then as long as the alternator was working, the engine would keep running.
My knowledge is very limited and so I am easily led by anyone who seems to know what they are talking about. I've used my phone a friend option so now I am asking the audience. Still have my 50/50 option.

On an earlier petrol that uses energy for the coil/s then maybe.
A diesel will keep running until energy is applied to starve it of fuel.

You want the draw down of the battery to prevent the alternator pushing an over voltage into the rest of the system. With so much electronic kit that could be dangerous.

Your battery sounds to be on its way out, although feasibly if not u/s could last the summer easily enough. If it's unable to support load though it could be u/s.
Tbh I would replace the battery as the more simple starting point.

 

[Alans dad]

I tested the voltage on the battery again today.
12.6 v with everything switched off.
12.2 with the engine running.
11.4 with fan, fog lights, interior lights and full beam on.
There was one point when the engine made a slightly different noise for a second and the reading went up to 13.7 then dropped back to 11.4v. It might have kept going up but it suddenly dropped back again. I am guessing that this was the alternator kicking in for a second?
Back to 12.6 after everything switched off.
Dodgy alternator?

P.S. New battery just delivered but have not fitted it yet. I read on the reviews of the company that sold it that they won't refund once the battery has been fitted. If it turns out that my alternator is faulty and my original battery is OK then I want to return the battery in brand new condition for a refund so I am hesitant to fit it. I imagine the terminals will show some marks once I fit it. Maybe I could wrap a little tin foil or thin metal around the terminals to fit it and test the alternator so they still look new. What do you think? Or should I just keep the new battery?

 

[Alans dad]

check the voltage at the back of the alt from underneath.

Will do this tomorrow.

 

[mioba]

I tested the voltage on the battery again today.
12.6 v with everything switched off.
12.2 with the engine running.
11.4 with fan, fog lights, interior lights and full beam on.
There was one point when the engine made a slightly different noise for a second and the reading went up to 13.7 then dropped back to 11.4v. It might have kept going up but it suddenly dropped back again. I am guessing that this was the alternator kicking in for a second?
Back to 12.6 after everything switched off.
Dodgy alternator?

P.S. New battery just delivered but have not fitted it yet. I read on the reviews of the company that sold it that they won't refund once the battery has been fitted. If it turns out that my alternator is faulty and my original battery is OK then I want to return the battery in brand new condition for a refund so I am hesitant to fit it. I imagine the terminals will show some marks once I fit it. Maybe I could wrap a little tin foil or thin metal around the terminals to fit it and test the alternator so they still look new. What do you think? Or should I just keep the new battery?

Sounds like the Alty pal,

give it a wack with a rubber mallet

 

[M80]

I would check for poor connection at the alternator, but it sounds like voltage regulator by the sounds of it.
Can anyone local refurb your alternator?

12.6 volts is good enough for a battery.
The alternator should be more than capable of compensating for any load applied.

 

[Alans dad]

Checked voltage directly from the alternator. There was no increase in voltage so it was not putting anything out. I forgot to check the plug in connector that supplies the alternator, so maybe it could be that little lead or even a fuse??. I removed the alternator and then removed the regulator. The brushes look ok to me but I don't know what they should look like. I measured them and I measured the distance into the slip rings. It looks to me that I have 5mm more length than needed to make contact. So they would definitely be brushing against the rings. What can I test with the alternator off the van?

 

[Alans dad]

Can anyone advise me of what tests I can do to find the fault with the alternator on the workbench? I think the brushes are still O.K. (see my previous post).
The clutch system seems to be fine i.e. When I put a screw driver in to the cooling fins it freely spins in one direction but will not turn in the other direction.
I can't see any discolouration, burn marks, cracks or any thing visual that looks wrong. The brushes are at least 5mm longer than gap ( I mean they will have to compress the brush springs at least 5mm when the regulator is fitted on and pushed against the slip rings). How and what can I test next?

 

[Alans dad]

I didn't know what else to do to test/fix my alternator so I went and bought (part exchanged) a reconditioned one from an alternator shop. Cost me £140.
I fitted the new one to the van and then found that the electric supply plug would not go into the socket on the new one. They looked identical on the outside but inside the socket there are three tiny plastic ribs/locator lugs and they were a tiny bit different to my plug. Out by about 1 or 2 mm, just enough to make it impossible to push the plug in properly. So I took the alternator back to the shop. They pushed cut the the lugs out of the new one and gave me £10 for my troubles. Fitted the now altered new alternator and after a struggle with the fan belt and tensioner got it all going again. Fixed that problem and now on to the next.... Fuel injector leak / black death.
The answers and suggestions to my questions suddenly dried up three posts ago. I hope it was because no one knew the answer of what to test on the alternator. I am sorry if I unintentionally upset anyone or maybe I didn't follow the correct forum etiquette. Anyway, thanks for all the early helpful advice peeps. I wouldn't have dared to do this job without the help of the forum.

 

[mattkh]

Well done.
The plug to the alternator, did it have any sort of a locking system, just hoping that the modification did not make it easy to slowly come off with vibration.

 

[M80]

Glad you have the alternator problem sorted.

I can't see that anyone would be upset by your posts, like mine some times they can be a bit long, but if you have issues and want more help keep 'em coming.

I've not read all of your injector thread but it looks like that issue is coming along. I haven't needed to use pullers so can just wish you good luck there.

 

[alexanderfoti]

On an earlier petrol that uses energy for the coil/s then maybe.
A diesel will keep running until energy is applied to starve it of fuel.

You want the draw down of the battery to prevent the alternator pushing an over voltage into the rest of the system. With so much electronic kit that could be dangerous.

Your battery sounds to be on its way out, although feasibly if not u/s could last the summer easily enough. If it's unable to support load though it could be u/s.
Tbh I would replace the battery as the more simple starting point.

Older ones yes, anything with an ECU won't run without power

 

[Alans dad]

Thanks everyone. I know I write long posts, sorry about that. I do it partly because I am hoping that my thread will help a future Mercedes owner/reader who is in the same predicament and as confused as I am. When I am reading other peoples posts/threads and trying to learn something, I often wish there was more info or clarity for us ignorant readers. The very helpful experts on here often naturally use terms or abbreviations that leaves newbies confused and bewildered. I am trying to get the balance between keeping it simple and plenty of detail. Thanks again guys. I love this forum.

 

[Alans dad]

Here is picture of the inside of the Alternator socket and the inside of the plug. There are three guiding lugs, two on one side and one on the other. Notice that they are not perfectly centred. But the plug is off to the right while the socket is off to the left. Why can't they manufacture them the same? Grrrrr!
Don't make the same mistake as I did (the shop did).