Alternator query

[chris.richard]

My Bosch alternator has a spade terminal marked W and I'm not sure what to do with it. Tha Alfa wiring diagram shows a capacitor attached from a terminal to the casing - is this what it's for? If so, what sort of capacitor is it? Does it go to earth via the casing?:confused:

[Cloggie]

Hi Chris,
At last someone has asked a technical question on the forum that I can at least part answer! Who said that those folks that just buy their cars complete can't help sometimes.....

I'll need to check the W terminal on my car when I get home, but I do remember I also had the same redundant terminal when I recently replaced the alternator.

However, the Capacitor you mentioned is to prevent any electrical noise being generated from the current developed by the alternator being heard on over speakers for any electrically sensitive in-car entertainment devices (Car CD/Radio Cassette Players) I picked one up from my local Auto shop, and didn't seem anything too specific to the particular alternator.

I'll check on the Terminal when I get home tomorrow night and update you. Cheers, Nico/

[chris.richard]

Ahem!

[Cloggie]

Hi Chris,
Apologies for the delay in getting back to you on this one, but last night, after weeks of waiting, I finally had the opportunity to get into the "missionary position" with my car (I was underneath..) and check the alternator as promised.

The W terminal is not connected up on my car either, nor is connected on my 1991 Alfa 164 run-about car. I think it has something to do with cars with Airco (mine doesn't have it) and it was a separate signal back to the wiring loom, but that's all I know.....

The rest is as per my previous message, wth the live screw-thread terminal , and the neutral "push" terminal being the only 2 connections on the unit.

I replaced my alternator with a brand new exchange unit after the old one developed a fault. It had a slow dripping water hose connector above it which eventually corroded the internal windings. I tried to dismantle it and repair the fault but it was a bit of a nightmare job.

So , I decieded that given it's in such an alkward place to get to, and that I want it to be reliable for a long time to come (it's a pig's ear to remove it due to it's position - Fuel tanks out, the lot....) I opted for a new one....

Hope this helps, and apologies again for the delay in responding.

Cheers, Nico/

[chris.richard]

Thanks Nico. I'll ignore it until the neighbours complain about tv interference!

[David May]

Just in case anybody is feeling bad about leaving terminals unconnected, some higher-output alternators have a battery voltage reference terminal (Bosch won't say why its called 'W') which allows the alternator to sense the true battery voltage regardless of the loss in long (or undersized) power cables. If the output cable is short or sturdy there is little difference anyway.

Dave May