Replacing alternator- connections help please.

[fredrussell]

The Hitachi alternator on my 3gm30 has ceased to output. I’ve removed it and will get it overhauled locally. Ages ago I was given a Prestolite alternator and, if possible, I’d like to fit it whilst the Hitachi is refurbished and keep the latter as a spare. Physically, both alts are the same but connections differ:

Connections on Hitachi are:
B+ (charge output to battery)
B- (negative output/ground)
L (warning light)
R (ignition/12v)

…and connections on Prestolite are:
B+ (charge output to battery)
B- (negative output/ground)
D+ (warning light)
W (tachometer)

Are these alts interchangeable? The tachometer feed on 3gm doesn’t come from alternator so I realise I just ignore that connection on the Prestolite but the R terminal on Hitachi has me a bit stumped…

 

[PaulRainbow]

The Hitachi alternator on my 3gm30 has ceased to output. I’ve removed it and will get it overhauled locally. Ages ago I was given a Prestolite alternator and, if possible, I’d like to fit it whilst the Hitachi is refurbished and keep the latter as a spare. Physically, both alts are the same but connections differ:

Connections on Hitachi are:
B+ (charge output to battery)
B- (negative output/ground)
L (warning light)
R (ignition/12v)

…and connections on Prestolite are:
B+ (charge output to battery)
B- (negative output/ground)
D+ (warning light)
W (tachometer)

Are these alts interchangeable? The tachometer feed on 3gm doesn’t come from alternator so I realise I just ignore that connection…

Yes, interchangeable. Just ignore the tacho connection on the Prestolite and insolate the ignition connection from the Hitachi.

For sorting the Hitachi, Nacton Auto Electrics have always given me good service.

 

[fredrussell]

Thanks Paul - when you say “insolate the ignition connection” is that a typo? If so do you mean isolate or insulate please? I assume it’s isolate…

 

[VicS]

Insulate it so that you can reattach it when the Hitachi is refitted.

If you intend to never refit the Hitachi you could disconnect it from the ignition switch.

 

[fredrussell]

Ah, ok cheers Vic

 

[PabloPicasso]

Ah, ok cheers Vic

When my alternator died 16 years ago it was not worth getting it refurbed

There were lots of worn out parts, bearings, brushes as well as electronic issues.

Alternators are not tge eye wateringly expensive items thay once were, so made no economic sense to get the old one repaired.

We have a prestolite and its been fantastic. You'll likely never need to replace it again.

Here is a diagram of the connections.

 

[fredrussell]

Well, seems I have two alternators that need looking at! No dice with the Prestolite. I’ll do a bit more fiddling/checking and then start another thread.

 

[PaulRainbow]

Well, seems I have two alternators that need looking at! No dice with the Prestolite. I’ll do a bit more fiddling/checking and then start another thread.

Take them to Nacton Fred. He's a good guy, won't rip you off. If they aren't worth fixing he'll tell you, usually no charge for testing them. If you need a new one his prices are good.

 

[PaulRainbow]

Thanks Paul - when you say “insolate the ignition connection” is that a typo? If so do you mean isolate or insulate please? I assume it’s isolate…

Typo Fred, should say insulate. Or it could be a new word, combining insulate and isolate

 

[lustyd]

could be a new word

No, insolate is definitely already a word. Not sure why you'd need to expose the wire to the sun though!