Alternator

hi
I'm looking for a replacement alternator for my boat that has a ford anglia engine in
The current alternator is a prestolite ALK 6207 5A
I'm assuming any will do the job as long as the mountings match ?

I was getting a reading of 12.2 volts at the battery with the engine running
And 12.4 volts with the engine off
Also my amp guage stoped working
Am I correct to think it's the alternator .?
Any help appreciated

 

It sure seems like an alternator fault!
The original would have been a Lucas ACR more than likely, but if you can find one to fit -including the pulley alignment - all should be well.
John

 

Probably started off with a dynamo! Has the Prestolite got an external regulator? Photos might help

 

It's from the USA! Wonder how it came to be fitted to a 105E engine? I'd have thought you could fit a Lucas one , there's normally some adjustment available or you could use some washers as packing. Make sure the pulleys line up and get the connecting plug .

 

Yes some of the conversions was done using a Ford Fiesta alternator
I'm not sure if the one that's currently on there has a built in regulator ?
The wiring on the boat is very basic (and messy)
I'm assuming the external regulator was removed as I can't see anything connected anywhere
The current one only has two wires I'm assuming positive and earth ?

 

No. All it will need if you fit a 3 pin Lucas alternator is the big wire connecting to the battery positive (or starter motor solenoid main feed - same thing) and a switched 12v ignition feed to the thin wire. Feed this through a bulb and that will be your ignition/charging light. The earth will be through the alternator body.

 

Usually the two wire system has one charging output wire (the thicker one)and one that goes to the charging light on the dash board.....the earth being taken care of by the alternator casing and car engine block. Id guess this alternator has its own regulator.
John

 

I found an exploded view of that alternator on the web, and fairly sure it doesn't have a built-in regulator. On your 3rd photo, the aluminium box on the right could be an external one. Most likely faults are brushes and regulator. If your brushes look worn and you can get hold of replacements, worth trying that. The external regulator is probably a vibrating-contact type, and cleaning the contacts and adjusting it might cure the problem.

 

Thanks everyone for your advice
And after some adapting of the old mounts
I have now fitted a new 75 amp alternator
I'm assuming the box in the picture was the regulator from the old system I have removed it but do I need to do anything with the wires
One red and one blue I can't find where these go as the wiring is a bit of a lash up
But I do now get 13.4 volt at the battery with the engine running

 

The box is the regulator (quick google). Both wires will have been between the alternator and regulator. Now it's all internal to the alternator so the wires are redundant. You could remove them or just tie them up somewhere neat.

 

That's great I will just tape them up them
Just as a matter of interest my alternator has only two wires attached one is obviously the charge wire so would the other have gone to the regulator ? And then from the regulator to ???
Many thanks for the help

 

It could go to the charging light on the dashboard - does your system have such a thing?
John

 

No I only have two lights one says hot and the other oil but I have never seen them on
I do have an amp gauge but haven't a clue how that's wired
The alternator has two wires one thick brown one and one smaller blue one
The regulator also had two one blue and one red on terminals marked I & F
And it says negative ground I'm assuming that's trough the metal case
The blue one may be the one from the alternator but it comes out of the wiring loom from the opposite direction ?
At least it's charging now but I would like to know where it all goes for future reference

 

I think Peter.N is likely to have more idea than me, but I'll scratch the brain cell and give it a bash.....
The heavy duty lead goes straight to the battery, without a fuse. Diodes in the alternator prevent any current flowing the wrong way. I think this terminal could be marked B, or B+.
If you want to use an ammeter, it must be strong enough to handle all of the current the alternator can provide (70 amps or whatever). However, a 'shunt' ammeter can allow only a small amount of current through to register a charge. The larger current is allowed to bypass the meter.
The other terminal, sometimes blue, sometimes marked F may be used to operate a charge lamp. Its not as simple as that however, because the electricity to operate that actually comes from a switched live from the battery, to the charge bulb, and then to the alternator.....this could be used to provide an 'exciter' current for the alternator.
If you want to check if your battery is charging, use a voltmeter instead. These wire directly across the battery terminals and tell you what the voltage is. However, you don't want it to register all the time as it will eventually flatten the battery, so it is fed by a switched live, i.e it only operates when the engine is running.
DISCLAIMER!! Alternators are physically tough but electronically fragile. Reversing polarity of the battery or even allowing them to spin without the battery connected will goose them. So, be very careful if you fiddle.....it could be best to engage an auto sparky for an hour or two.
A simple check on your system.....connect your multimeter set to more than 12v across the battery. With engine off, see around 12v, maybe. On starting up, this voltage can decrease to around 10.5 but not much lower. Engine running, expect something around 14.5v.
If your battery loses charge over a couple of days for no apparent reason, disconnect the battery and see if it retains its charge.
John