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Discussion Starter #1
Yes, another rev counter issue from someone who seemingly just hasn't read all the available info. Well, i've read everything i can find and still no avail.

Have converted my 2001 ABL to AHU from a 96 Golf. Got her filled with oil and coolant yesterday, bled her through and off she went no bother. Happy days. I'd already removed the old 'W' wire (red) from the ABL loom and put it in the AHU's alternator 2-pin connector in the 'W' position (cos i'm clever like that), then ran it to where it originally went in the T4, which was plug F pin 9. No joy though.
Now, when i went to remove the wire from the plug (fuesbox end) i realised i'd put it in pin 10. Did i write down pin 9 by mistake or did i put it in pin 10 by mistake. Wouldn't mind clarifying this. Reason being that i did have something at the rev counter. I've video'd this and put it on the tdi conversion facebook page if anyone's interested.
After pointers for what i should have done i then connected the red W wire to plug G1 pin 12. Still nothing. I belled the wire through ok. My meter doesn't have a frequency function so i'm unable to test W on the alternator but this i pre diode and the alternator is obviously working (it did in the Golf) so i'm thinking this won't reveal too much anyway.

Are there any suggestions?

Blue clocks. Always did have an issue with the oil pressure warning with the ABL which is why i tested the wire continuity. This is obviously now a different alternator too with just the B+ W D+ terminals.

I'd very much love for one of you to call me a and say, "you missed this off...you " and the day be saved......
 

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Discussion Starter #2
A quick check of the plug (F) and there is no pin 10 on either T4 or Golf fusebox, so it was pin 9 it went to.
Worth noting i also have the battery light on but when the connector on the alternator is removed it goes out. Tried to check voltage here but meter not picking any AC or DC up. It does get 12V on B+. I think this should be around 14V though. Just wondering about the alternator itself...
 

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Discussion Starter #3
Alternator isn't doing anything. Only 12V at B+ when running, slightly high when not so i'm only reading battery voltage.
Nothing coming out of D+, however it has 12vdc and 24 vac feeding into it. Am i right in thinking this is ECU controlled excitation?
If the regulator inside the alternator is knackered (D+ goes to it) and the rotor doesn't receive this excitation, will the W terminal, which i understand is tapped from the stator also do nothing?

Please, all help much needed. Thanks
 

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NOTHING to do with the ECU.

12 volts should come to the "exciter" connection via the bulb in the dash.
Once started (and charging) the feed from the bulb, will be the same as the output from the alternator....hence the bulb goes out.

" however it has 12vdc and 24 vac feeding into it."

It should have only a supply from the bulb (12 volts ish) into it.
Where the hell did you get a 24 vac supply from?!!??!?! :confused:

The W terminal is taken from one of the windings before the diodes, to give an AC output, the frequency determined by the revolution speed of the alternator.

If you don't get the voltage to the D+, the alternator will not produce any charge.

IF you have 12 volts at D+ (ign on, NOT running) and you don't get a charge, chances are regulator/brush pack faulty.

You won't get 14 volts until the alternator starts charging.
 

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I would try and sort it out one bit at a time, leave your W terminal disconnected, and try and get the charging working first.

Get one of those old fashioned small 12v test probe things, one with a bulb in it (not an LED) and connect one end to your D+ and put the other end on the + of the Battery, and this should work exactly like the warning bulb on the dash.

So with the alternator not rotating it should put out a ground path to illuminate the bulb, as its getting ground at one end and the 12v from the battery end of your test light.

Once the alternator is running the ground path goes away, and you get something in the region of 12v on the D+, and because your test light now has 12v at both ends, the bulb will go out.

The bulb has to be in the circuit as the power for the field current has to flow through it.

If the bulb doesn't even light up with the alternator not rotating there is something wrong with it, and the same if the bulb lights and doesn't go out when running.

Is the alternator the one from the AHU? And are the terminals marked up D+ and W, as about that time you do start getting some of the early DFM (digital field management) alternators, which are DF and D+ and the 2 pin plug is nearly identical.
 

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Discussion Starter #6
NOTHING to do with the ECU.

12 volts should come to the "exciter" connection via the bulb in the dash.
Once started (and charging) the feed from the bulb, will be the same as the output from the alternator....hence the bulb goes out.

" however it has 12vdc and 24 vac feeding into it."

It should have only a supply from the bulb (12 volts ish) into it.
Where the hell did you get a 24 vac supply from?!!??!?! :confused:

The W terminal is taken from one of the windings before the diodes, to give an AC output, the frequency determined by the revolution speed of the alternator.

If you don't get the voltage to the D+, the alternator will not produce any charge.

IF you have 12 volts at D+ (ign on, NOT running) and you don't get a charge, chances are regulator/brush pack faulty.

You won't get 14 volts until the alternator starts charging.
Cheers mate.

re: 24vac - who 'kin knows?!?!:* but it's there i assure you. Which puzzles me as the only ac thing on the engine is the alternator, which appears to not be working
when the plug is connected i get the battery light, when disconnected it goes out. I'm only measuring when it's disconnected as that's when i can get the probe in. I found in Penbryn's guide that D+ is fed from Plug F pin 3 so i'm past wondering if the ecu has owt to do with it.
I was trying to find a guide on how to test the reg but no cigar. the brushes and slip rings have contact but worn. there's continuity from the D+ terminal right through to the slip ring but i don't know if this proves the function of the reg.
 

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Discussion Starter #7
Is the alternator the one from the AHU? And are the terminals marked up D+ and W, as about that time you do start getting some of the early DFM (digital field management) alternators, which are DF and D+ and the 2 pin plug is nearly identical.
It's the AHU D+ W type.

Cheers for that. So one end on battery +ve and the other on the alternator with the plug off?
 

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Discussion Starter #8
Found an overhaul kit for the alternator for not much money and replaced slip rings, regulator. Still no output from alternator (12.1v)
Witt meter on diode mode I can get a reading between b+ and the stator one way but not the other, so that seems to make sense although don’t know if it proves anything.
Any ideas? Can’t find any shorts.
 
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