Diesel Alternator

Hi Guys,

got this ongoing issue with my alternator.

Orgionally it was not charging after going throw some mud. The dash light did not come on, just stopped starting one day.

Replaced the bush's as they were really gone, charged fine for about 2 weeks. Same again, no charge and no battery warning light.

When you ground the cable going from alternator to dash both the low battery and water in diesel light comes up on the dash.

Replaced the alternator with another td27 one that the previous owner said was working. No charge.

the D21 manual says for the ka and Vg alternators if you short the wire and the dash light comes on that the regulator is most likely broken.

does not mention both he low battery and water in diesel light coming on at the same time.

Does anyone have any idea why these two lights would come on? are they linked or do i have an issue here?

christian

unkn0wn said:

Orgionally it was not charging after going throw some mud. The dash light did not come on, just stopped starting one day.

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When you say, stopped starting, did it turn over at all? Did it indicate a dead battery, ie. radio doesn't work, headlights very dim etc? If all other indications are that the battery is holding charge, and the starter didn't turn over at all, then the problem is your key barrel or starter solenoid. If the charge light didn't come on but the battery isn't holding charge, I'd blame the battery OR a poor connection on the back of the alternator.

unkn0wn said:

Replaced the bush's as they were really gone, charged fine for about 2 weeks. Same again, no charge and no battery warning light.

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See, the way that light works is that one side of the bulb is fed 12V through the same fuse as what runs the glow plug timer (do your glow plugs work fine, by the way??), and from the other side of the bulb runs into the alternator (yellow with a black trace) and acts as an excitation current; this is what makes your alternator work. Once the alternator is excited and is turning and producing current, the voltage on both sides of the bulb lifts to 12V, and the lamp goes out. If the charge from the alternator drops below 12V, the lamp will gradually start to get brighter and brighter as the voltage out of the alternator drops. This is what indicates to me that your alternator is alright.

unkn0wn said:

When you ground the cable going from alternator to dash both the low battery and water in diesel light comes up on the dash.

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This is to be expected - see the above explanation. With the water-in-diesel light, that light remains illuminated whenever the ignition is on but the engine is not running (I don't know what the logic is behind that but that's how it is); that information (used by the glow plug timer also to shut the plug cycling off) comes from the alternator voltage. No current, engine must be off, lamp is on.

unkn0wn said:

Replaced the alternator with another td27 one that the previous owner said was working. No charge.

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This makes me think even more that the alternator isn't the issue.

unkn0wn said:

the D21 manual says for the ka and Vg alternators if you short the wire and the dash light comes on that the regulator is most likely broken.

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These are both vehicles with ECUs, hard to compare to the basic wiring on the TD27.

unkn0wn said:

does not mention both he low battery and water in diesel light coming on at the same time.

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Petrol vehicles don't have water in diesel lights.

unkn0wn said:

Does anyone have any idea why these two lights would come on? are they linked or do i have an issue here?

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Answer the above and I think we can track this down pretty easily.

Fusable link ?

Dave said:

Fusable link ?

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Not fitted to D21s with TD27

Battery leads? terminals tight?

reel-sensation said:

Battery leads? terminals tight?

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Either of these, or a dead battery too? Could be the alternator is working, but not charging the battery for one of these reasons. In which case, no alternator light, but you will eventually get a flat battery, or a battery not in circuit with the engine. Jump start it and test the voltage on the actual battery terminals, not the leads, while the engine is running. Rev the engine, and she should go up to 14V or thereabouts. Try the same on the alternator output and see what you get.

Wow, epic post, thanks Dion.

It stoped starting due to dull battery, you could tell it was going flat as the starter would have less juice. I was just putting it on the battery charger once or so a week.

Something sus is going on with the electrical system. When key is ign, the battery light or water light would not come on unless u grounded the alt wire.

I just cut the wire I fixed up for the glow plug relay and these lights came on while the car is off (how they should)
*previous owner cut it and wired in a switch, i wired it back in because the timer was working. nfi why he unpluged it.

still no Alt charge tho and the bat/water lights go out as soon as the car is started.

the bat maintains same/similar voltage as before started and you can watch it go down if you turn on the lights.

obviously there is something electiraly broken going down here.....

Pinelli said:

Either of these, or a dead battery too? Could be the alternator is working, but not charging the battery for one of these reasons. In which case, no alternator light, but you will eventually get a flat battery, or a battery not in circuit with the engine. Jump start it and test the voltage on the actual battery terminals, not the leads, while the engine is running. Rev the engine, and she should go up to 14V or thereabouts. Try the same on the alternator output and see what you get.

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I replaced the terminals when I got the car
redid the ground and cleaned the positive wires as it was a bit coroded.

normally its around 12.6 - start then at idle was 13.2ish and 14.5 at 3k

atm its 12.5ish and 12.5 when running, no matter what rev. if you turn the lights on, or wait long enough you can watch ti drop.

but it usually takes about 10 starts and 10 hours of radio before the battery refuss to start the car again. I can easily drive it to work for a week without needing to charge it.

If i drive at night i need to charge it pretty much straight away and the lights get dull after 10 mins, but thats to be expected (ps ive only dont it twice and the bat dident get to low to damage it)

battery itself seems fine. I do carry a spare, just incase.

Can you describe in more detail all wires that have been cut, rejoined, switched etc? Locations, colours, every detail.

Since the lights go out when the engine is running, that indicates the alternator must be producing a charge, since there's no other way for that light to turn off, UNLESS the circuit has been changed.

Also check the chassis ground on the passenger wheel arch under the bonnet (clean, remove paint etc). Check the connections on the back of the alternator to make sure they're snug and clean. The regulator is built into the alternator so changing alternators eliminates that. Don't you have a TD27 AND a TD27T now? Can you swap alternators around to test with a third alternator?

Colour alludes me. Its the signal wire from the timer to the relay/ this was cut at the relay, so the timer was unable to control the glow plug relay. a switch was wired in here.

only have two alternators, on from the na and one from a turbo.

just realised i dont have the little thing connected to the ground wire. looks like a small metal cylinder.

It was connected to the na pump, couldent find it just them, dont knwo where i put it

:/

would this be the cause?

No, that's just a capacitor. It's supposed to stop the alternator causing a whine on your radio. It won't stop it charging.

The glow relay wire doesn't sound relevant either. I'll think some more.

What effect did swapping the engine over have? No change?

Hook up a multimeter from the positive terminal of the alternator, to the negative terminal of the battery. Output should be 13V+.

unkn0wn said:

Something sus is going on with the electrical system. When key is ign, the battery light or water light would not come on unless u grounded the alt wire.

I just cut the wire I fixed up for the glow plug relay and these lights came on while the car is off (how they should)

still no Alt charge tho and the bat/water lights go out as soon as the car is started.

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You cut it just now?

Which of 1, 2, or 3 in the image below did that wire you cut run to? With the ignition on, and engine on, check the voltage between each terminal of "3" and the negative terminal on the battery and post the results here.

number two...

there is one little wire going in there, thats triggers the 12v to the glowies.