discharging question

jan bogert

jan bogert

Senior Member
i recently took my altenator off my '38 flathead. i put the generator back on. my question is i went to a cruize on sunday, yesterday the volt meter said 3 volts. when i was driveing on sunday the volt meter read 7.2 good. could the cut-out be bad and draining the battery when sitting? and if so, i have a couple good model a cut-outs could i use one of them?
 
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A full charged 6 volt batt should show 7.2 volts when driving. I did you get the engine started on 3 volts? It must have charged itself up on your trip. Walt
 
driveing was 7.2, it sat for 4 days and when i went to the garage it was to go somewhere it was reading 3 volts. could a bad cut-out cause this? and if so will a model a cut-out work on my generator? JAN.
 
If the points in the cut out don't open when the engine is off, the battery will discharge through the generator. I think a Model A cut out is the same, they are just a 6 volt "one way switch". If your battery is going dead when the car is parked something is drawing current. If you just put a generator on, the cut out would be a likely suspect. Try the Model A cutout, it can't hurt anything.
 
Thay make those cutouts now with a diod instead of the points. The points have a habit of sticking closed that will run down the batt with the engine shut off. With the diod the jouce only goes one way and won't feed back with the engine off. Walt
 
thanks guys, the generator was sitting for awhile, so i'm going to put a model a cut-out on i know there new. JAN.
 
Jan...I posted everything I know plus a lot more pirated from several 1950's manuals in an old post:
http://www.jalopyjournal.com/forum/showthread.php?t=278956&highlight=generator+tests&showall=1

Start with full-fielding, which will tell you whether gen or reg/associated wiring is the trouble, then try motoring the gen before getting more elaborate.

And firstest of all POLARIZE the thing before doing anything else. In this and all the other stuff be sure you are reading the posts thart are about FORD, as people kept stepping in with Delco polarizing info (wrong and possibly destructive on Ford) and tests in general have to follow the Ford type wiring.

Polarizing: http://www.jalopyjournal.com/forum/showthread.php?t=256038&highlight=generator+polarize&showall=1

Simpler testing:
http://www.jalopyjournal.com/forum/showthread.php?t=278956&highlight=generator+polarize&showall=1
 
The early cut out type just get flashed between the 2 terminal on cutout. Repro cutouts are pretty flimsy inside, look for an original and clean the contacts as a start.
All the round ones are fundamentally interchangeable with only minor changes over the years.
 
Coupla more things...cutout is just an on-off switch with amperage set by the third brush adjustment, so 2 relevant tests: If you bypass cutout with engine running at a high idle by jumping across the 2 terminals, you should see a charge on ammeter if gen is good.
If you suspect welded points on cutout, generator will motor on battery current but you will have to loosen fan belt to get it moving...it can't spin the engine.
 
A diod is is the best way to go. When a cut out fails it could start a fire from the resistance , when they stick closed it's a completed circut to the generator and because the generator can not spin the engine it will heat up, I have seen them melt the solder in the armature. They were always a problem. When a diod fails it would be an open circut, hence no back feed. They are sold by many of the current suppliers, don't take any chance on a old cutout.
 
You can buy the cutouts with a diode with Ford script from several venders and you can not tell them from the original cutout on the outside. Marv
 
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