alternator problem

Hi.
I have done a search but can't find anything that quite answers my questions. Last week I changed my old 2.5 petrol for a 200tdi. All went well and it's running driving.
But I have a charging issue. At rest the battery reads 12.38, At idle testing the alternator voltage reads at 12.22. At the moment I'm carrying two batteries. When I rev the engine the voltage stays the same. If I unplug the alternator and retest it shows 0.5 volts. Is this normal. From What i imagine the alternator should still charge. As soon as I put my headlights on the voltage drops to 11.99 and doesn't go up until the lights are off. So I'm guessing the alternator is fooked. Just want someone to confirm before I go to brookwells.

Sorry for any spelling mistakes longest thing I've written on my phone haha.

Cheers,

Lloyd

OK - the alternator will not charge or do much of anything if the plug is unplugged - it needs the connections to do anything.

From what you're describing I'd suggest you either:

a) don;t have the alternator hooked up right (Big lead to + battery, little lead to lamp and the lamp socket to +12 on the other side)
A1) If the bulb in the dash for the alternator is bad it can stop 'em charging - is the light coming on at rest?
b) the alternator's not working.

Did this 200TDI come out of a running vehicle, and is the alternator known good? Check the wiring and see if that's right, and then get over to an auto electric shop with the alternator and have it tested.

Lastly, did you rev the engine or is this at idle/start? Some alternators take a bit of revving to start charging - the one in my 110's like that.

ajr

A correctly working alternator will charge at about 14V + / - 0.2V.
The fact you are registering just over 12V at rest (I assume you mean with the engine off?) means the battery is good so yes, I would say your alternator is faulty.

The battery at rest (engine off) is 12.38. With engine running wether at idle or being driven or even just revved is 12.2. I have bought a new one anyway will fit it after lunch. The engine is a defender unit which apparently was removed as the owner was converting to a monstrous V8. Thre are 3 wires into the plug, 2 thick brown wires and a brown yellow one.

check that all 3 have 12v when the ignition is on

Re: Plug:

2 thick brown leads are output and are essentially jumpered together internally. LR was too cheap to buy good-diameter wire...

The thinner lead is the one back to the lamp. Grounding that should turn on the lamp.

As said above - see that all 3 have +12 on them. if not, then they need to (blown bulb will cause the alternator not to charge!).

Thanks everyone. Will give it another go tomorrow. My engine is a defender unit with a disco turbo and manifolds. The top bolt for the alternator, the long one will have to be cut off as it is obstructed by the exhaust manifold. Will see if I can find a replacement one lying around somewhere.

mrchurchill109 said:

Re: Plug:

2 thick brown leads are output and are essentially jumpered together internally. LR was too cheap to buy good-diameter wire...

The thinner lead is the one back to the lamp. Grounding that should turn on the lamp.

As said above - see that all 3 have +12 on them. if not, then they need to (blown bulb will cause the alternator not to charge!).

Click to expand...

you dont really need the 3 wires from a 200 dti engined alternator, as one wire is the rev counter wire, well thats whats on my 92 reg year disco.
long story but I needed another alternator last year, found/was donated a volvo 740 one, made it fit, but only had 2 wires coming out of it, the third wire was rev counter - not used.
that was a temporory repair I bought a new one for my disco, its still in its box, in the storage box in the back of my disco over a year later.
it charges up to 14 volts on start up, but runs around 13.8volts upon warming up. forgot all about my rev counter after a while..

my disco never fails to start, its got two batteries linked as 12 volt but lots of cranking amps to spare, I even "drove it on the starter" 1st+ reverse gears, a couple hundred meters when my timing belt went..