Club 80-90 Forums

Ive just swapped my old CS 1.6 diesel motor with a 1.9 AEF engine from a Polo. It starts and runs just fine (yipee!).
BUT i have a head scratching problem with the alternator. Its the one from the polo (a bosch 90).

On the old alternator as fitted to the CS engine it had 2 red wires ( I know these go to the battery) and one blue wire which connected to (I assume) the charging light on dash panel .
The polo alternator has the red wire (to the battery) and two extra wires. One blue (from D+ terminal) and one Green (W terminal).

If I connect the blue D+ alternator wire to the blue wire connected to dashboard, then the charging light illuminates when I turn the ignition on and soon goes out when the engine is running - seems pretty normal to me. BUT when I turn the ignition off and pull out the key, the engine keeps running! I can only stop the engine by seperating the blue wires.

So I tried connecting the blue dashboard wire to the Green (W terminal ) wire on the alternator. The red light comes on the dashboard ok, but does not go out when the engine is running. But at least the engine stops when I turn off the ignition.
Any clues as to what |I need to do??

W terminal is for the rev counter.

Might be worth having a read of this guide?

http://www.brick-yard.co.uk/forum/16cs- ... ine#428158

Thanks windysurfer for the info on the green wire

I used colinthefox walkthrough guide to help fit the engine but it just says to join the alternator wires up which I have done. I cant understand why the engine doesn't stop when the ignition is turned off.

Hmmmm.

Seems to me your connections were OK first time. I didn't say which wire went to which cos I didn't see any way it could go wrong.

Do you have a Haynes Manual? I know it only does p****l models but the relevant bit is the same for oil burners too.

Wiring diagrams 12.29 has the black wire from the ignition line (which also connects to the injection pump solenoid) arriving at the instrument cluster at line 43. The blue wire arrives nearby at line 45, with a diode, the charge LED and a resistor in between. The diode appears to be to stop the alternator backfeeding the ignition system via the instrument cluster. Is it possible you could have fried the diode? If it was fried or shorted or there was some other sort of wiring fault at the instrument cluster, I think it could produce those symptoms.

You could try pulling off the instrument cluster connector with the engine running, to see if that stops the engine. If it does, then the fault would appear to be in there somewhere.

The other thing that occurred to me was if you had a split charge relay connected to the blue wire, and there was some kind of problem with that, maybe it could backfeed somehow, but I've no idea how that might work.

Please let us know how you get on. Best of luck.

Hi Colin. Thanks for the excellent write up - I wouldnt have chosen the AEF conversion without it

Its been suggested that the fuel cut off solenoid could be at fault (the 2 black wires going to the immobiliser?) Seeing as I had a 50/50 chance of getting the feed/earth wires correct i wonder if i guessed wrong? I was going to swap the 2 wires over and see if that made a difference.

It doesn't matter which way round you connect the two black wires.

You can check the function of the solenoid by listening as you connect/disconnect it from 12V. You should hear it clicking.

In the end i fitted a simple switch at the dashboard to cut the ignition when the key is removed. Seems to work but I still dont know why it behaves like it does.

Wierdest thing now....I had the spare wire from alternator which was the Revcounter feed. So I decided to fit a revcounter and now the engine stops as expected on the ignition key. Dunno why but it has solved the problem .