Griff 500 Preserp which Alternator

[waggy]

Hi,

My Alternator has failed after 31yrs loyal service. Tested it, whilst engine running, no voltage coming out. only see battery voltage on main terminal to Earth. Seeing 12.6v on Excitor when disconnected.

My question is, after searching Forums I cannot find the exact replacement. Its a 1994 500 preserp. one of the first 500s built.

Theres no label on it or code numbers, only that its a Magneti Marelli , the voltage regulator is 28000B 20 93

Motoclan List it as EO462 which is out of stock, asked and they cannot say when they are available. £117.94

some say its a Lucas A127 75A L/H which i can get from CJF Auto Electrics for £66

Or Land Rover Defender 200TDI STC233 £79.99

AutoDoc AEA1227 £151.51 but picture is of a R/H fitment not same as mine.

I would prefer a Motoclan one as it should definitely Fit but they are out of stock.

Racedirect are also out of stock. no indication of when they will be available.

Could anyone point out the best alternative... I don't want a cheap Chinese one.. but i don't want to pay £300-£500 as some Land Rover sites are quoting.

Thanks

Alex

Edited by waggy on Wednesday 17th September 11:17

Edited by waggy on Thursday 18th September 10:07

Edited by waggy on Friday 19th September 21:52

[Belle427]

Maybe it would be cheaper and easier to get yours refurbished if you can find somewhere local to take a look.

[waggy]

Thanks for replying, I tried looking for a repair centre but can only find garages that replace alternators.

I can replace it myself, just need a suitable replacement. Im going to strip it and work out what has failed. if its the Diodes or Voltage regulator I can replace them reasonably.

[waggy]

I stripped and tested the Alternator, windings are okay all correct resistances , rectifier tests seemingly okay between casing and B+ terminal = 0.458mv (diode test).

therefore ordered a new voltage regulator. fitted it and refitted alternator to car, started engine, red light stays on, checked output of Alternator and seeing battery Voltage 12.5v. so still not working.

What i did notice. if the excitor wire is disconnected, when i turn on ignition theres 12v on it. when i connect excitor wire to alternator i see 2.4v.

is this correct, does the voltage regulator draw this amount of voltage without engine running.

cannot think of anything else. Anyone know if this is correct, tried googling it, but no info.

[Belle427]

The exciter wire comes from the dash warning lamp and when ignition is switched on engine not started the alternator grounds it to bring the lamp on.
When the engine is started it puts a similar voltage on it to cancel the lamp.
Cant explain the internal circuitry sorry but cant see it being anything else really, the 100 amp fuse down on the chassis would not cause this and i dont think a pre serp has one.

[waggy]

Thanks for replying. My car hasn't got a 100a fuse.

Managed to find a repair agent who tests and repairs alternators will get them to test it and work out the problem.

Alex

[sixor8]

I'm slightly surprised at that. I knew early cars didn't have them, but your profile states you have a 500. Perhaps they were only fitted from the Serpentine engine onwards?

[waggy]

Update - Took alternator to a repair specialist. He put Alternator on a testbed and found one of the 6 diodes had failed.

sold me a new rectifier set for £12. stripped Alternator and unsoldered old rectifier and soldered in new one.

fitted to car and now running perfect. HURRAH,,, now seeing 14.5v on output.

Saw on internet that if you connect meter (set to diode test) - positive probe on Casing and Negative probe on B+, if rectifier okay should see 0.4v-0.7v. and Open cct leads reversed. This is rubbish, it only tests 2 diodes out of 6. There are 3 phases in the Alternator with 2 diodes in each phase. The only way to test properly is to unsolder recifier and test each phase.

Im now an expert on Alternators,

Alex

[Belle427]

Nice repair, did you do it yourself?

[waggy]

Yes. You were right to find a specialist. Quite easy to replace rectifier .. also replaced brushes on voltage regulator. They were quite worn

Alex