27 Buick Generator Diode???

[Weaklink]

My dad is rebuilding a '27 Buick.  He live 3,000 miles away and does not have internet access, nor can he send me a pic on his phone.  He says there is a diode between the battery and generator.  He says it flows both directions and he wants me to order a replacement.  Any idea what this part is called, or what size I would order?  I did a Google search and saw some Power Generator Rectifier Diodes.  Most have metric studs on them.  Any info would be appreciated.

[Jim Nelson]

In todays world,  buy him a simple cell phone.   The inexpensive iPhone from Apple (my wife has one) is great.   The learning curve is short and the local phone shop would answer  and get him going.    I even got my 84 yo buddy using 'facetalk'.   It makes our world SOOOO  much easier.   ( don't let the phone shop try to up grade ).    He and I now 'show' what we are talking about.   JMHO   ( ya,  I'm just a kid - 79 - but I could not do my Buick issues with out the photo function). .     My Buick friends are all over a hundred + miles away so questions can be hard to work with.   

[Str8-8-Dave]

There was not originally, a diode in the circuit from generator to battery.  That is a band aid added by someone to replace a missing current cutout relay or cure a generator discharge issue likely caused by a faulty generator that can only occasionally, probably at high engine rpm, raise enough voltage to charge the battery.  In a case like that the generator is probably discharging the battery by letting the battery's higher voltage flow back thru the generator where it is wasted by making heat in the field windings.  

[Weaklink]

So is the correct answer to insert a current cutout relay, or have the generator rebuilt?  My father has never run the engine yet; bought it as a basket case.  He is finishing-up wiring.  Probably prudent to have the generator tested and go from there?

 

Sorry so vague.  Trouble-shooting long distance is painful.

[Mark Shaw]

14 minutes ago, Weaklink said:

Probably prudent to have the generator tested and go from there?

Yes...

[Str8-8-Dave]

9 hours ago, Str8-8-Dave said:

missing current cutout relay

I should have called this device simply a cutout relay.  There is a current limit relay up under the dash in many of these early Buicks but it's purpose is circuit protection, it's a crude and not real effective replacement for a fuse panel.  Pictured below is a Delco Remy cutout relay that mounts atop the generator on this 31 Buick and has only one wire out that routes to the ammeter which keeps track of whether or not the battery is being charged or discharged.  That circuit then feeds the battery. 

 

 

[Oldtech]

I suspect the cutout has died and someone replaced it with a diode from an electrical store so best: get the proper cutout. second best, another diode replacement but they have to be able to handle the amperage . would  need to be 30 amp or better. These generators are built to last 100 years.