How goes it? My Daughter's boyfriend rather stupidly put jump leads on my van the wrong way around & did some damage. I replaced the alternator with another I had & the van still wouldn't work, I replaced the voltage reg on the bulk head, I also had to rewire the alternator as the main lead to the starter motor had all melted. It all worked fine after this, I took the alternator off & put the original one back on when I connect the battery the charging light on the dash comes on, when I turn on the ignition the oil light comes on & the charging goes off, once started the oil light goes off & the charging light comes on half brightness. I notices=d some sort of regulator on the back of the alternator under the black metal cover can this be changed on its own as I believe its this that is faulty or am I wrong? Hope I've made my problem clear & not confused you its a Bosch 55 Amp by the way.
I should imagine that something has cooked in the original alt... I'd take it into a place that reconditions them, and get it looked at!!
Slightly off subject but this is what happens if the PO forgets to connect the bell housing / chassis earth strap - and a new alternator too please!! Hope you get it sorted Mr B
The "thing" on the back of the alt is likely the diode pack, which will have been well cooked. New or recon alt time!
LOL he knows he's a knob. I got him helping me clear out the garage as I'm too nice to make him pay for a new one.
DOH! that looks a bit manky, Mine has an earthstrap luckily. (I think anyway) I'll certainly check tomorrow.
No as far I'm aware (although I've never had an alt with an external regulator). Two bits of gubbins: the diodes that rectify the AC current from the coils, and the regulator that keeps the output voltage up according to load. Could be wrong, but as far as I'm aware, they're separate units. The diodes live inside the alt.
You could well be right. I'd like to find out how it all works. I have to do a bit of digging I think.
Mmm you could be right. I think the external bit is just a reg, not sure how it works its like a relay & has 3 wires direct from the alternator.
Yeah, all type 4s are external reg... But thinking about it, the rectifier has to be in the alt, otherwise the reg would connect directly to the battery and not the alt!!
Here's something similar. Pic shows both an internal or external regulator. The diode pack, which needs good heat-sinking, lives inside the alt (part 37). I've you've reversed the polarity of connections to the alt, I'd expect one or more rectifier diodes to have gone pop. http://www.1800vw.bizhosting.com/0.alt.htm
'Tis true what I say, honest . The regulator monitors the output voltage and, if it starts to drop when say you've turned your headlights on, increases the rotor coil current to compensate. Internal ones also hold the slip-ring brushes. The rectification of the AC waveforms from the coils - your alt is basically just a 3-phase generator - is done by hefty diodes that potentially get bloody hot!
