Knackered Alternator?

[Wilma]

Help from electrical man please. T.25 with AAZ engine. Alternator seems to have ceased charging the battery. Battery charged up and the van starts fine but after a few journeys the starter won't turn over and we are back to the cycle again. When charged up and running all electrics, lights etc work fine. A voltmeter across the battery with alternator connected and engine not running shows 12 volts. With the engine running it shows about the same.
I have cleaned the terminals and connections between alternator and battery. Alternator is a VW 65 amp one and probably ten years or more old - may be original to the van (1989) or to the engine (mid 90's). I had similar trouble about a year ago and this traced to the brushes worn. These were replaced and no more trouble. I have checked these and they are long, clean and sliding freely. With the engine off, battery charged, the headlights are bright so I believe battery earth system OK. Alternator belt correctly adjusted. One small point though. When you switch on the battery charge light on the dash does not light, nor does it flicker or come on when running. The other dash lights come on and go out as they should. Can this mean anything or is it a seperate problem, say LED blown. If there is a problem with the bulb or wire to dash would it affect the charging system? What have I missed or has the alternator died? I can't think that the faulty dash light would stop it charging - but my electrical knowledge stops after I have changed a torch battery.

Is the colour of the wire at the dashboard end the same as the one at the alternator? Is it the same one which runs without change from front to back?

If alternator has died does anyone know if the AAZ needs a dedicated alternator to that model engine or can you fit one from a standard 1.9 T.25 diesel. This really means can I get one from Just Kampers or Brickworks? Any help much appreciated.

[bigherb]

If the battery light does not come that indicates a problem with the charging system. First disconnect the blue wire from the alternator and with the ignition switched on, touch the wire to earth (clean metal part of engine), use a paper clip or something in the wire connector to make the connection if necessary, the battery warning light should come on, this checks the warning light circuit which starts the alternator charging. If the circuit checks out then there is no earth path through the alternator for the warning light circuit to work either the regulator is faulty or the brushes are not making contact.

[kevtherev]

usually the brush pack is worn out or broken.

[ghost123uk]

Certainly sounds like a duff alternator to me.

Safety first = DISCONNECT the battery(s) before touching the wires on the alternator

Either get a used on from the breakers, you can find one that will fit and have the same connectors on many German cars, take the old one with you as a pattern to compare with.
Make sure it has the same pulley on as yours as they can be a sod to get off (though you might have to settle for one with the wrong pulley and hope they can be swapped over OK - ( heat is the trick !)

Or ask in our "wanted" section to see if anyone has a spare = quite likely, billy739 near Bristol often has them.

Or just get a new Alternator ( I use "Europarts" for good prices and quality )

Or, as Kev says, take a chance on it just being the "brush pack" that bolts on the back of the alternator with 2 smallish bolts (it often is that, but not always) and get one of them (about £12 on Ebay - make sure you get the right one there are 2 different types)

[Wilma]

Thanks, fellas,

I think we can discount the brush pack as a new one was put in 12 months agao and is still long and moving freely in its holder. I then followed Bigherbs instructions and found that when I removed the blue wire from the alternator, battery connected and ignition on, and then grounded the blue wire to earth still nothing happened. No battery light on the dash. I checked the blue wire from alternator to engine junction box and got continuity. Chosing between the LED blown and the wire running the full length of the van I chose the LED. After much cussing and swearing I got it out but how do you check one? can you do it like a bulb with full 12 volts test from the battery? I am suspicious of it as a continuity check across the wire pins shows no continuity but I don't know if that is good for an LED. In any case, if the LED was blown would that stop the alternator charging? Can you just buy them from somewhere like Halfords or are they wattage rated like bulbs? I am too old fashioned to have had anything to do with these new fangled contraptions.

Should it not be the LED but a broken wire does the blue wire from the engine junction box come out in the ignition switch or the dashboard? As you know the connection to the dashboard printed circuit is a long multi-pin plug but there does not seem to be a plain blue wire entering it. I suppose I could run a long test wire all the way from front to back but I don't know what to connect it to at the fron end. Its all too difficult and giving me a headache. I am in the wilds of Cornwall and a long way from a good VW auto electrician!

[ghost123uk]

The LED does not run off 12V directly.

It runs off about 2 volts, this is achieved with a small resistor in the wiring close to the LED.
The voltage applied to the led HAS to go the right way round (and it is not clear as to which way this is by the way !)

It is unlikely to be blown, and even if it was it wouldn't stop the alternator from working.

Fire the motor up and CAREFULLY put the red probe of a digital multimeter, set to read 20V DC, (~£5 from Maplins etc) onto the nut on the back of the Alternator that has a fairly thick red wire going to it. (with the black lead from the meter earthed to the engine block)

The reading at a fast(ish) tickover should be around 14 Volts, any less than 13 and a half and the alternator is almost certainly duff.

Take care with that red probe wire from the multimeter onto the red wire and it's mounting nut on the alternator, don't let it touch any other metal parts, even when the engine is off, as it goes straight to the battery positive !

[Wilma]

Fixed it - and many thanks to all those who helped. For anyone's benefit this is what happened. I finally decided to have another look at the brush set and took it out - it is one of those with the regulator combined. Brushes undoubtedly OK so I took a torch and peered down the hole from which the set had come to check that the brass strips of the commutator? were clean and not worn. All OK. Then I noticed that hanging down inside the cavity is a piece of forked brass which makes contact with the back of the brush set when you screw it home. This looked dirty so I cleaned it with a bit of emery and slightly bent it out into harder contact when the brush set was screwed home. The brush set holder has itself has a metal facing which completes the contact. Cleaned that up. Put all back and started up - 14.8 volts! So that's what it was - I had no idea this contact existed and you need to stand on your head and use a torch to see it, but it is as important as the brush contacts themselves.

Now the only thing I have to do is fix the problem that I did not have before I tried to fix this one. No oil light and no charging light. Suspected charging LED so took it out and broke it! Then in order to make sure I had the right one took out the oil light LED to try it in the charging light hole and when putting it back probably put it back the wrong way. As everyone warns about the fact that they are polarity conscious and you cannot tell one terminal from the other I had carefully marked it on one side with a felt tip. Remembered too late after I had put everything back that I had turned the instrument panel the other way up when I re-assembled!! Ah well, that will keep for another day. Incidentally, LEDs are very difficult to get hold of. Tried two big factors in the area and neither stocked them. Halfords had - but only 12 volt ones. Try internet search next.

Thanks, everyone

[ghost123uk]

Incidentally, LEDs are very difficult to get hold of. Tried two big factors in the area and neither stocked them.

Thanks, everyone

Maplins = about 15p each !! = buy 10 and have a play

If you peer inside it you can see 2 x "legs" inside it (known as Anode and Cathode)
1 is larger than the other and has like a tiny "flag" shaped thing, whereas the other is small and more like a straight "stick" - the one that is smaller is the +ve feed

They also have a "flat" on the outer rim, though I cannot remember how this orientates with the + and - legs

btw - a cheap 1.5 volt AA or AAA torch battery will power one up, but will not (usually) blow it if you get it the wrong way round - (note NOT re-chargeable or HD types like Duracell etc)

To run a std LED on a 12 Volt supply requires a resistor in series with 1 wire of around 1000 Ohms ( about 5p at Maplins - the smallest size will be fine) As far as I know, the ones fitted to dashboards have this resistor built into the wire, very close to the actual LED.

[Wilma]

Hi, Ghost,

Sorry to be a pain in the neck when you have been so helpful. These LEDs. Mine are a little colored bulb with two legs sticking out like pins. They are quite long, about 7mm (I measured one) and on each LED one 'pin' has a kink in it, presumably to tell negative from positive if you know which is which. They are nothing like the ones I see on Maplins Internet Site in which the 'legs' seem to be set in glass. I think they call them wedge. Obviously in mine the pins slide down into two 'holes' and they would not fit the wedge type. Were different types fitted? On my setup there appears to be a single resistor mounted on the instrument case from which a fine wire goes to the printed circuit - presumable serving all of the LEDs.

Seems the only answer may be to try and get an instrument panel from a scrapper and pinch the LEDs - if I can find one. I am fourty miles away from nearest Maplins but when next in Plymouth I will go in and show them mine and see what they come up with.

Won't bother you again after this - promise

[T25Convert]

Hi,

Just to jump in here - pretty sure these are what you need (5mm LED with 'standard' legs).

http://www.maplin.co.uk/Module.aspx?ModuleNo=2047" onclick="window.open(this.href);return false; they are 39p, with £2.99 P&P to have them sent straight to your house. Don't buy the super bright ones advertised - they will blind you at night!

Maximum reverse voltage is 5v, so even if you put them in the 'wrong way round' they will not blow. Just pop them back out and try the other way round.

As a guide each LED is fitted the same way round in the dash, so have a look at the one for the indicator which is still fitted correctly, and make sure the other two look the same!

LEDs aren't like bulbs, and very rarely blow. If your LEDs aren't lighting up there is a good chance there is a problem where the main connector joins the dash. With the ignition switched on (and the LEDs all back in) give the connector a gentle wiggle and see if any light up.....

Cheers,

Alex

[ermie571]

Got a maplins on the doorstep....

can post to you if you want.

Think I may even have a spare dash in a cupboard somewhere....may trundle down to maplins with it and see what they can offer me!

Em
x

[ghost123uk]

Sorry for the late reply = been away for a day !

Looks like Alex and Em have answered the question though

Were you mixing up std LED'd with those little "capless" wedge shaped glass bulbs ?

Let us know how you get on ( "here to help" = could be an 80-90 motto )

[Wilma]

Thanks Alex and Em,

Have ordered direct from Maplins. Why couldn't I find them. Blame senility. Will let everyone know what happens. Van charging OK now, all lights working - except Charging and Main Beam! Charging is blown - I helped it I think. Main beam was working before I took the dash out last time to fix the oil light which was not working but is now! All on hold now until LEDs arrive. Has anyone out there got fingers about 8 inches long and as thin as matchsticks?

Malcolm

[Wilma]

Back again fellahs. Finally got round to diving into the dashboard again (twice) and fitted new red LED from Maplins into the charging light slot. It now works, comes on to start with, goes out when engine starts and stays off for a while. Then, after about five minutes, it starts to flicker faintly on and off, very rapidly. I also notice that at night the headlights and dash lights do the same. It only very slight, hardly noticeable, but its there. Alternator checked at the battery with engine running shows 14.6 to 14.75 volts. Being a digital meter there is a slight variation up and down - 0.1 or so up and down but, checked against the car, the same variation is there. The flicker wasn't there before all this happened. Any ideas, anyone? Belt is still tight. Alternator dying perhaps? Incidentally, the LEDs from Maplins are 5 volt whereas someone said earlier that the ones originally fitted are 2.5 volts - could this be the reason for the flicker? I don't think so but I am no electrician. All I notice is that the charging lght is slightly brighter than the oil light.

Malcolm

[T25Convert]

Hi,

If you ordered the LEDs from the link I posted above they are rated at 2.5v (don't be led astray by the 5v reverse voltage quored - this is how much they resist going through them 'backawrds' - ie with the legs connected the wrong way round).

However, whatever volatge they are, I don't think they will be the cause of your flicker.

If all the lights flicker then it seems the voltage is dropping slightly, so the charge light may well come on. It suggests that something is still not really right with the alternator. You may not be able to capture this with your multimeter however, if the time of the voltage drop is very short.

Suggestions as to why it only happens after 5 mins:

1) alternator starts to warm up. Electrical resistance increases with heat, so less power is getting through.

2) the choke comes off, so the alternator spins slower. If you rev the engine, I assume the flicker goes away?

Sounds like a new alternator might be on the cards.

Alex