'49 Cub: Battery drain and high oil pressure

Moondoggie · Nov 26, 2010

My '49 Cub has 2 problems. First, with the magneto start switch 'off' or 'on' there is a drain on the battery, enough to wear it down completely. Is there a spot I should look at for the drain? Second, the oil pressure stays high - to the far right of the gauge. Took the spring out of the oil pressure relief valve, but the valve is stuck. Any suggestions to get it out? Thank you. Hope your Thanksgiving was quiet and fattening.

rustyacresnd · Nov 26, 2010

I wouldn't think the mag would have anything to do with a battery drain since a mag isn't powered by the battery. Instead I would probably go for the voltage regulator. Connect a test light in series between a battery cable and the battery post. If the test light lights up, then you have a drain. If not, then you probably have a battery with an internal drain. If you have a lit test light, then start disconnecting wires, one at a time. When you disconnect the circuit with the drain the light will go out. I would probably start with the wires to the VR. The VR contacts can stick, causing a drain. Hope this helps.

Moondoggie · Nov 26, 2010

Thanks. I'll fire up the workshop woodburner and try that tomorrow.

gene bender · Nov 27, 2010

off on sw has nothing to do with that problem as it is just a grounded sw to kill the mag. Your voltage reg or cut-out must be sticking to drain the batt ar further yet are you sure your battery isnt at fault. When you slow the engine speed and then stop the engine the ammeter should deflect some to O.

John T · Nov 27, 2010

Like the other gents noted if it has a Magneto that should have NO affect on the state (charge or discharge) of the battery. All a mag kill switch does is to electrically connect a mags kill terminal to frame ground when in the OFF position

AS far as the discharge, if its a very fast discharge and a working ammeter shows high discharge (and genny gets hot) after you turn off the tractor, that can be a sticking closed Cutout Relay. If thats the case if the belt were loosened the genny will spin like a motor but if you removed the wire off the VR or Cutout Relays BAT or GEN terminal it stops turning, THATS THE PROBLEM.

If its more of a slow trickle discharge and it takes a long time before the battery is discharged, theres a short somewhere. (or the battery itself is bad, have a shop test it) If thats the case and if you remove the battery cable she does NOT discharge THATS THE PROBLEM.

The URL link below can help troubleshoot the cause of non charging.

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=665110

John T
John Ts Troubleshooting

Janicholson · Nov 27, 2010

I will add to this informative thread that you could have an alternator, not a generator. An alternator will (likely) be aluminum and rather blocky in appearance. A generator will be cylindrical and rather long, 7 inches or so. If it is an alternator, none of the information below about the drain is valid.
A magneto is still not connected at all to the electrical system, so that is correct. (it also assumes you actually have a magneto)

Do this if it has an alternator. After rrunning it, or charging the battery, remove the big wire from the alternator (carefully as it is a 12 volt hot wire) and put a test light between it and the stud you took it off of. If the test light glows even a little, that alternator is in need of repair. If it is bright, it probably has a bad diode in the output bridge. Good luck, Jim

Moondoggie · Nov 28, 2010

Thank you for all your comments. It is a magneto and it is a generator on a Cub. 6 volt system. The generator brushes and commutator look very good. The regulator has no markings for 'GEN', 'BAT' or 'F'. How do I know which terminal on the reg. is which to connect to the generator and the ammeter, etc.? There is a wound resistor, a fixed set of points and a moveable set of points in the interior of the reg. I'm lost but the drain is still there, with new wiring. thanx again!

Moondoggie · Nov 28, 2010

After further review . . . . it's not a VR, it's a cutout. I found a great diagram, in a 9-2010 discussion, done by farmallbob.. thank you farmallbob. The wires as connected are not correct and I'll reconnect them tomorow. Let you all know if I get a charge.

'49 Cub: Battery drain and high oil pressure

Moondoggie

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rustyacresnd

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Moondoggie

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gene bender

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John T

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Janicholson

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Moondoggie

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Moondoggie

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