Alternator connections

[Jcorstorphine]

I have a Ford 1.6 (hand knitted) diesel engine which I have been in the process of marinising. I have a question about the Alternator connections. On the rear of the unit there are a pair of large spade terminals which are commoned together. In the same recess as the first two, there is a third smaller terminal which is not directly connected to the two large spades. There are two other connections marked B+ and W on the backplate which are insulated.

I assume the two large connections carry the main current back to the battery and I believe the W is for a Tachometer. I believe there should also be an exciter connection which is taken back via a diode. My question is what are the other connections for i.e. the B+ and the small connection beside the two heavy ones. Also what should the rating of the diode be.

Regards
John

 

[pyrojames]

B+ is your main output, and may have a bolt terminal in parallel with the spades. Use the bolt if possible as I find the spades have a tendancy to heat and increase resistance. W is the Tacho. The remaining is a the connection to your indicator light for charge D/D+/L on some alts. The unit sounds like a Lucas type A127, and will probably have an internal reg, as I understand it, no excitation circuit required.

 

[gandy]

Some alternators of this type are "kicked into live" by the warning light circuit. The one on our digger is like that. With too small a bulb in the warning light the alternator doesn't charge at all, or if its a little too small then the alternator doesn't "wake up" until the engine's revved a bit.

I suppose what I mean is don't miss off the warning light, as it might not work without.

 

[Billjratt]

A photo, or at least the type and model of alternator in question would be useful. There are quite a few variations.
What (vehicle?) did it come from - can you get the diagram/information from there?
The two big terminals (in a "T" configuration??) are probably B+, the smaller adjacent one is probably IGN, and there could be a plug that carries all the neccessary connections available(go to a car scrapyard).
This type of alt has a chassis connection for the negative (B-) side, so if you are considering an isolated engine installation, you'll need to make appropriate alterations.

 

[Jcorstorphine]

Many thanks to all for the help. I did a search for "Lucas type A127" which turned out to be my unit. Have also realised that I did not have a connection through a bulb and have been advised that it should be in the order of 1.3 w. Just in case I had fried the diodes, I took the unit to a local Alternator repair shop who tested it and found it to be OK so will get it back on the engine and wired up.

regards

John