cosworth_wannabee

hi all, i have just got a new alternator off the net as my old 1 was giving up on me. Its shaped exactly the same so it will fit, the only thing is the electrical side of things is a bit different. ive put a pic of the 2 below to show what i mean. the original i just took off just had 2 wires on the alternator. the new 1 has 2 parts where wires are too be fitted too, as shown in the pic circled in green, but i am worried about the spade connections found which i have circled in red, am i missing something or are these nothing to worry about and should i wire it up as the old 1 was?!?!

the old alternator says b+ and d+ for the wires and the new 1 says W and B.

any help on wiring this would be great cheers.

iansoutham

I assume that your RS has a heated windscreen as the old alternator is a 70A one.

The two spade terminals on the alternator on the right are generally only used with 55A or lower alternators. The other connections are probably for different types of car with bolt-on terminals as standard.

The W output is a single-phase output normally used for things like Diesel revcounters.

The D+ output would be the blue wire for the battery light on the dash
The B+ output would be the big red wire from the battery/starter motor.

I would say you have a 55A alternator supplied, not a 70A one. Check the label on the side of the alternator to confirm.

cosworth_wannabee

hi, its a 75 amp alternator, well so the seller tells me.
so shall i just wire it up as it has been already and not worry about the spade connections?? cheers

mk4gartrac

I was running a big ice system on an old mk4 rst and killed the alternator so was advised to put a 90amp one from a granada v6 with full electric pack the only differance is the puly is a bit bigger but it went straight on and never had problem again

iansoutham

As long as you wire it up as above, i.e. B+ to battery, D+ to blue wire and leave the W alone, it should work fine.

Once running, I would get the available output checked though as I am still suspicious.

cosworth_wannabee

ok kool, but on the new 1 there is no d+ only b+ and a w, so should i put the d+ to the w???

tabetha

On the NEW alternator the smaller spade terminal, in the same slot as the two larger ones, is for the warning light, so this would be where the D+ needs to be wired to.
tabetha

cosworth_wannabee

ok thank you very much. so i havent got to worry about any of the other connections. jus the d+ to smaller spade and larger wire to b+. thanks all

tabetha

Yes, that's all you need, as you've said.
tabetha

JesseT

Yes, teh two larger spade connector are both B+ and should both be connected as one cannot carry the amperes alone.