Alternator/Battery warning

[rallen]

Hello
The car displayed this warning today and all lights appear dim and engine is not running very smooth.

Came back from work, measured the voltage with engine on, about 10 Volts, revving made no difference. It should be 13.8V with engine on so seems like alternator is dead? But I read a short battery cell may cause same behaviour. I will try to run the engine on another battery.

Failing that I looked at the alternator (it is getting rather dark outside) and could not see any obvious "regulator" component I could perhaps pull out and repair/replace. Any ideas where such a component may be located? Are there any relays/fuses perhaps that might cause problems?

This is a E320 2001-2002 estate petrol engine.

DOh! engine off and the battery voltage is shy off 12 volts, looks like the battery is good... I do not even knwo where the battery is (trying to find it)

many thanks

 

[Ultymate]

Rallen I think the battery may be in the rear of the car and usually nowadays the voltage regulator is built in to the back of the alternator and usually includes the brushes which may be worn out if they are be sure to check for wear on the slip rings that the brushes run in contact with. Hope this helps

 

[rallen]

I think it is under the rear seat, about to start taking covers off. But the alternator, practical guide of how to remove it please?

 

[Ultymate]

According to a schematic I've got open on my PC the alternator is below the fan and slightly towards the O/S of the vehicle and as far as I can see has 2 wires to it and is mounted on 2 bolts ( no nuts) but what I can't tell from the diagram is how buried by other components it is and obviously you'll have to remove the serpentine belt which drives it. First thing I would do is make sure you've got a good 12V+ connection on the main terminal of the alternator before you start removing it

 

[Ultymate]

Another thing to check is whether your ign warning light is working on the dash as that is used in the ind circuit to excite the alternator ie if the bulb has blown it will cease to charge:-? Also according to my PC program on some models "E" series theres a connector in the n/s footwell between the battery and the alternator which on "some" versions contains a fuse for alternator protection so a blown fuse or dirty connection here could cause loss of charge. I hope this info is correct that I'm giving you I'm getting it from a 2 disc program I bought on Ebay so fingers crossed

 

[rallen]

The dash is all electronic. I looked at the alternator which is highly visible and it looks like it is secured with 2 bolts. They are like positive torx screws though, I do not have such a tool. Further there is the belt for sure and also other "plumbing" around it, in effect I cannot see the surely beefy cables that should be leaving the alternator , so I guess they are at the back and out of view. So first thing I need to do is to buy the special tool for those special bolts. Regrading the fuse at the footwell, could you please be a bit more precise where I can find it? We are talking passenger side front? There are some wires and conectors/relayes type thingies I noticed under the rear seat next to the battery I will go have a look now in case they are associated with the battery.

 

[rallen]

ok here is what that connector/thingy looks like, it is under the rear seat on the other side of the battery

 

[Ultymate]

All it says is theres a connector in the N/S footweel it does'nt say front or rear even and all models except engine types112 and113 it contains a fuse for alternator protection.

 

[rallen]

OK I looked under the footwell, lots of thick red wires on a huge connector, no fuses (unless it is a big round thingy, all wrapped in tape alongdide the thick red wires), just a big connector with bolts it seemed. On the fuse boxes (one near the battery and one in the engine compartment) there are three 30A and 40A fuses, all good. It must be the alternator - regulator.

Bad news: I am covered by MB roadside assistance but have exceeded my service by 5800 miles... So they will not cover me.

Additionally I have a 3 year mechanical insurance, but have when I take the car to the garage to be repaired they may also say the same (service interval exceeded by 1.5 months and 5800 miles)....

Finally the garage is in Guildford and I cannot drive the car there, not on a rapidly discharging battery...

Doh!

I wish I could remove that alternator myslef, but I cannot even see how to take the belt out, it seems to be very well tensioned. Any ideas?

 

[television]

You are diving in the deep end. Batteries do go open/short circuit in one cell taking the voltage down to 10v, the car will not run very well at this voltage if at all.

If the alternator was faulty the lamp would be lit on the dash, this lamp comes on before you start the car, so it is not the lamp or the alternator. I do not know what meter you have, the meter has to be in serries to measure current and be capable of measuring 10 amps min

disconnect the battery and try and charge.

The battery is now some 4 years old and coming to the Max of its life.

I have a car here right now where the max voltage when charging is 11 volt, it pulls everything down in the car.

malcolm

 

[rallen]

Battery is good, charged overnight. The alternator makes a whining noise, I think it's broken. Need a new alternator.

How do I remove this one? There is a belt that goes around with no obvious tensioning levers. Perhaps the alternator pulley is the one that tensions the belt?

Any advice on how to take it out appreciated.

 

[television]

Battery is good, charged overnight. The alternator makes a whining noise, I think it's broken. Need a new alternator.

How do I remove this one? There is a belt that goes around with no obvious tensioning levers. Perhaps the alternator pulley is the one that tensions the belt?

Any advice on how to take it out appreciated.

Have you thought about just changing the regulator on the back, it unplugs cost £15.these include the brushes and diodes.

Malcolm

 

[rallen]

stick my hand in at the back and pull? It is quite tight in there? No screws or anything to keep it in place?

 

[rallen]

what it looks like

 

[television]

They are held on with 2 10mm nuts, you may fine this useful.

http://articles.mbz.org/electric/reg-repair/


malcolm

 

[rallen]

OK you may find this funny but I am stuck. Took two big coach bolts out of the alternator case thinking it would remove it from the angine block. But it is held on, seemingly with two big brass inserts and I do not know how to remove it!

here is a picture... all have been taken out but the alternator refuses to budge.

 

[Blobcat]

It sounds as if those are the bolts that hold the alternator together. Is there not a bolt in the bracket on the front?

 

[rallen]

Yes there were two bolts at the front and off to the side which have been taken out. Definitely holding the alternator on to the engine block. But there are two thick brass inserts/rings which are also holding the whole thing together, so even though the bolts have been removed the brass inserts are stuck in. As if hammered them in from the front. Here is a photo of the top front bolt position which shows the brass insert in place.

 

[kth286]

rallen

I replaced the regulator module, which includes the brushes (all in one compact unit) without removing the alternator. Just by removing the rear plastic cap and then unscrewing the module.

It was on an E320 petrol, but the previous straight six engine.

The part from Mercedes (called regulator) was £37 + Vat. Take your VIN number.

Do get the genuine article, and do remove the negative cable from your main battery before starting work.

Regards

 

[rallen]

It's OK. I removed the alternator now. As the previous pics show it is impossible to remove the regulator with the alternator in place.

Removing and re-inserting the poly-V belt is not easy, there is a tensioner pulley, very very hard to budge, I used two screwdrivers as levers on a special bit which must be there for that reason, to loosen the tension and remove the belt.

Alternator out, looks in pristine condition and turns without any noise. Checked continuity of thick wire from alternator all the wat to battery - all OK.

I removed the regulator bit (comes with carbon brushes) - looks also perfect but I suppose some diodes inside must be fried.

Will replace regulator and see.