Hey guys,

I'm overhauling my 120A alternator and have it all in pieces. The capacitor and regilator are all beimg replaced, as well as the bearings. How are the diodes? Do they live long and prosperous lives or do they die nastily and shortnoticed? As it is all apart and as you can get the diodes individually, I was considering tomchange them. On the other hand, it isn't that hard to remove the alternator when fitted so it shouldn't really be much hassle, just an annoyance...

Anything else I should check?

Body is being bead blasted
Pulley is being galvanized
Copper rings for the contacts will be cleaned up and edges removed
New bearings for front and rear pressed on
...

So what would you look at?

Cheers

Damien

 

Daim
I think removing the alternator is a royal pain! I vote change the diode pack.
Greg

 

Hmm. Is your engine bay any different to mine? As said, I thought is was easy to get to (with the radiator out etc.). Better than on the X308...

I can replace the diodes individually. Or better I can have a colleague solder them for me

 

What kills the diode pack and regulator is HEAT, if you replace them make sure they are heatsinked properly. In my experience I do not replace electronic components unless they are known failures or faulty.

Replacing the bearings is a good idea.

 

Well the bearings were shot. They didn't grind yet but there was enough slack to move the shaft on an angle.

As said, I am still a little unsere about the diodes. I know the alternator charged. The regulator though had a few little cracks so I bought a new one (from Hella, supposed to be more superior).

I think I'll just clean the diode unit up, see if anything is visible, give them a measuring with my multimeter and maybe then decide whether to replace or not.

 

You will not measure rectifier diodes reliably with a multimeter. I have seen large rectifiers measure good but leak when put under load.

If the Alternator was charging I would not replace diodes. A diode failure will take out either the regulator or the exciter winding depending if the failure is open or short circuit.

You can test the diodes in the alternator on the bench by connecting a battery to the B and a light to D terminal then spinning the alternator with your drill and measuring the AC ripple on the D terminal, should be less than 50 millivolts.

 

Cheers Warren. I'll just leave them then

 

Decisions, decisions. They just get more complex. My issue as to the diodes would be quality. The new ones may well be of lessor quality than the original and as such go bad quicker than the old ones?


Carl