What's that sensor?

Not sure what that is. It's linked to the alternator.

The blue thing? Looks like a big capacitor, probably installed to reduce ignition noise in the electronics.

Keith wrote:

The blue thing? Looks like a big capacitor, probably installed to reduce ignition noise in the electronics.

Click to expand...

No the white thing I circled in blue, attached to the engine.

*

Looks like an oil pressure switch.* Commonly used for alarm systems and to activiate alternators.

It could be a pressure switch into the oil system which could be used to prevent the alternator from trying to start charging untill oil pressure is up by interrupting the rotor, field, current from an external regulator.
Disconnect one of the leads when the engine is not running and use an ohmeter across the terminals. If it is a switch there should be infinite ohms, open switch.

Unfortunately it's hard to see where it goes on the alternator. Take a really good look at the terminal on the alternator that it connects to. There may be a cast or stamped marking next to it.

Try disconnecting it before the engine is started. If the alternator doesn't work then you have your answer. If it is indeed the rotor wire disconnecting after the engine is running would be ok but it's best not to. You don't want any chance of alternator damage of disconnecting while running if it is not.

I would agree with the oil pressure to enable the Alternator switch.

However similar units are sometimes used for other purposeses , like cutting off the starter when there is oil pressure ,



-- Edited by FF on Monday 15th of November 2010 04:47:46 AM

Thanks, I'll run some tests.