Alternator noise when headlights on?

[joneseythedog]

Dear All


I suspect that a newly-fitted alternator is not being driven properly in my C180:

* For the first few days after fitting there was some intermittent belt squeal, but this has gone now. I imagine that a few deposits have built up on the alternator pulley, giving a bit more traction now. There is some glazing on the belt, but it doesn't look too bad.

*The ABS light came on a few times too, over this period, but now does not. I understand that this happens when voltage is low.

* I fitted some extra-bright bulbs from Halfords in my C180 over the weekend after one of the existing bulbs blew (dipped beam bulbs). I can now hear a whining/ringing noise from the engine area when at idle or low speeds when the car is warmed-up, a bit like when fingers are run around the top of a wine glass. The noise stops when I turn the headlights off.

* The day after fitting the new bulbs, the car had a bit of trouble turning over at start-up.

Am I imagining things (esp. re. the noise stopping when I turn the lights off), or does it sound like the alternator is struggling? It is a Bosch remanufactured unit, and I had it fitted at a reputable independent.

Worn belt tensioner? B*ggered battery?

Any thoughts welcome!

Thanks,

Andrew

 

[Alex M Grieve]

More expert counsel will help with the question, but I would be very interested to hear your opinion on the brighter bulbs?

Worthwhile improvement?

 

[Myros]

the belt tensioner

would show up with a rattle and vibration, giving plenty of resonance at certain engine speeds. You'd certainly feel and hear it with a stethoscope on the block.
The new bulbs will only be drawing approx. 2x as much current as the old ones, or thereabouts, so it would be a poorly alternator that couldn't cope with the extra demand. i put brighter 100w ones in my high beam and it doesn't give the alt any grief.
Suspect the battery, or the diode pack thing or both on the alt. Best bet is run it over to an auto electrician and have him test the outputs.

BTW, I found the brighter bulbs made not much difference to the high beam, but couldn't be bothered changing them back. It's rare that I get to use them anyway.

 

[wireman]

Check the voltage at your battery both with and without running the engine and head lights.

If without engine and lights on the voltage is above 12v the battery is probably OK.

If with the engine on its less than 14v under any load (heads and rear window) there is insufficient power coming from your alternator.
Either a duff alternator or insufficient mechanical power to it is indicated by a low voltage, I would be looking first at the belt, pulleys and tensioner/damper for this one but it could at a slight chance be a faulty rectifier diode within the alternator.

I am assuming that the generator warning light is behaving normaly, if it is not working sort that out first since it plays a vital role in energising your alternators control circuitry (and keeping the ABS lamp out).

 

[television]

All of your problems seem to be with the battery from what you say, if it has a partial short circuit cell, it will pull down the voltage and decrease the charging rate.

Easy to check, it should be 12.5 volts before you start the car and 13.8 when the engine is running

 

[joneseythedog]

OK - I've borrowed a multi meter. I've connected it across the battery terminals and have found the following:

* Voltage without engine running after being left overnight = 12.5V

* Voltage with engine running and nothing electrical switched-on = 13.4V

* Voltage with engine running and lots of electrical things switched on = 12.6V. At this point things sound they are struggling a little in the engine compartment, with a definite squeaking coming from somewhere - can't tell whether it is the alternator or the tensioner. The squeaking stops when I turn a few electrical things off.

I'd just about written-off the noise as just a noisy fan this morning, but in light of the stop-start nature of the squeaking this doesn't seem so likely now.

I'm guessing the tensioner/damper is the cause, as this might be consistent with the belt squeal that appeared briefly after the alternator was fitted. I'll get it looked-at, but any other thoughts in the meantime would be appreciated. In particular, how would I be able to check the tensioner?

Andrew

 

[television]

Hi Andrew,,I am pleased that the voltages are all perfect

The tensioner is a problem sometimes, there are many post here on changing it,,I think that Anyweb did it a while back

http://www.detali.ru/cat/oem_mb2.as....418&VIN=*&CT=M&cat=19K&SID=20&SGR=045&SGN=03

Its easy to take the damper off to see it is still good, the idle rattles when gone,,its also possible the the belt is glazed

 

[Ellsy Tanners]

It is possible to fit the belt wrong on this engine, I dont mean to tell you how to suck eggs but its worth checking!!

 

[television]

As Ellsy

http://www.detali.ru/cat/oem_mb2.as....418&VIN=*&CT=M&cat=19K&SID=01&SGR=010&SGN=02

 

[chris heap]

noisey belt

if the poly v belt is not correctly fitted to all pulleys ie wider pulley than the rest, and 1 rib different it can cause a lot of squealing as i found out when fitting a new belt after replacing the tensioner. chris.

 

[joneseythedog]

Thanks to all for your help so far. I'll have a look at these links and check things over.

I've arranged to drop it into my local MB dealer near Hull (they've always been very helpful, and are happy to give a discount for older cars) next week, but might have a fiddle in the meantime if it is straightforward.

Andrew

 

[joneseythedog]

It is possible to fit the belt wrong on this engine, I dont mean to tell you how to suck eggs but its worth checking!!

Well, I bought a new belt this weekend. When I came to change it, the belt refitted by the garage when my alternator was changed appeared to be on the wrong route (or at least it wasn't the route shown in the Haynes manual).

I fitted the new belt on using the Haynes manual route, and all is well. The belt was easy to fit, once I realised how to take the tension off the old one - use a 15mm ring spanner on the pulley bolt. Turn anti-clockwise, and the tensioner moves.

I found Halfords in Hull very helpful when buying the spanner, btw - they gave me a bunch to try out in the car park. Didn't follow me out or anything, although I'd literally just walked in off the street/car park.

Now the belt noise has gone, I can enjoy all of the other noises so much better!