What alternator is this?

[jlatessa]

I have a double pulley alternator from a 1971 New Yorker, I think.
It has the dual field tabs, casting #s 4091424 and 105111 1
The large diode housing on the back, the housing castings cover all but 3 or 4 of the field laminations.
Total field lamination stack is 14.

Any help? Thanks
Joe Latessa

Need pics??

[jlatessa]

OK, more info, local NAPA tested unit and it failed due to DC volt output at 15.5.
Is this too high??

He also stated it's a 55-65 amp unit from and air-conditioned 70's car.

thanks

[Nacho-RT74]

by the casting number I don't think is earlier than 78 or so

I think the one you got is quite this on the right ( note, stator hidden down the housings ):



with this rear look ( left side ) called SQUAREBACK



and yes, they are on 60 amps average, although there was some what it were 78 amps. These alts are a little bit wider, need to cut a little bit the rear spacer AND will fit really tight into block location. Tipically, will need a longer belt to get an outer location from the block.

note...

earliers squareback looks like this ( same front housing and same side view with visible stator than old roundbacks )
where one of the brush isolators used on this is the same than roundbacks ( the one removed on this pic )



but the lates ones brush isolator replacing the one shown are more like a C shaped... the other one is the same

[jlatessa]

Thanks Nacho, mine is the one you have pictured.
What do you think about NAPA saying the voltage is too high (15.5), I thought the regulator takes care of this.

Thanks again for all the expertise you contribute, you are a wonder!!

Joe

[Nacho-RT74]

it was tested with a regulator or simply directly feeding fields ?

[John_Kunkel]

I have an alternator bench tester and the most I've seen on Mopar alternators is 15.2V but I wouldn't reject one for testing at 15.5V.

[69rtse4spd]

You da man John.

[jlatessa]

Thanks everyone, I'm going with it.

One other question, it has a double pulley, I'm assuming because it came from an AC car.
Will my single belt set-up align with the inner pulley or do I have to change to a single?

Are they easy to change withut ruining the bearings?

Thanks all...Joe

[elacruze]

What do you think about NAPA saying the voltage is too high (15.5), I thought the regulator takes care of this.

Yes, it's the regulator's job to reduce voltage. Unregulated alternator voltage is a function of field voltage and RPM. An alternator tester uses a fixed field voltage and fixed RPM, so has an expected output (which will be slightly different for every alternator design). 15.5v means only that your alternator is capable of making more voltage than necessary; installed regulated voltage can't be bench-tested.

Another test I always perform when changing alternators is an AC voltage test. If a diode fails in an alternator, you can still produce adequate DC voltage to operate normally, but the bad sector can produce an AC wave which may show up as radio noise or weird computer glitches.

A trick of the 'got-everything' offroaders is to take a big 120A Ford alternator, full-field it and use it unregulated for a welder. That's a pretty good illustration of what can happen if you wire your regulator wrong, or if a mechanical regulator sticks closed.

[jlatessa]

Thanks for the info Elacruze.
Alternator showed AC ripple voltage test as "passed" with ripple voltage value at 0.9

Joe

[maxwellwedge]

Even with a dual pulley your belts should line up fine. All 69-71 Hemi's used a dual pulley alt with a single belt.

[jlatessa]

Thanks for all the help friends..what a great resource this forum is!!!!!

Joe