[jetmech]

All:
I have a neighbor who shorted the positive terminal on his White LT 1650 lawn tractor. He cooked a couple of wires and the main fuse and I got it running without much trouble but the charging light on the instrument panel is illuminated and it is not charging.

There is a very small (1" square X 3/8" thick) two bayonet connector device in line to the engine (red wire) that my neighbor believes contains a diode. This device has Buss 253 marked on it but I have not been able to determine what the device is. If it does contain a diode, I am pretty confident my neighbor's short would have cooked it, as he almost certainly exceeded the peak inverse voltage for it. I don't have much for tech data on this machine but I found what appears to be a pretty good wiring diagram on Partstree. That diagram and parts listing does not contain any diodes but since the device in question is in the wiring to the engine, it may be part of the Tecumseh V-twin powerplant.

Any thoughts on this or anything else that may have been spiked and could cause the charging system to fail would be appreciated. I am trying to help out my neighbor with minimum cash outlay.

Thanks,
Jetmech

 

[30yearTech]

Without any model numbers we are somewhat in the dark. Most likely there was an inline diode in the wiring harness. They may not be illustrated in the IPL as most only list the wiring harness as a part number and do not show the diode as a replaceable part. You can replace the diode in the wiring harness if that's the setup it used and that should take care of it, as long as the alternator wasn't fried.

 

[jetmech]

Thanks, 30yearTech. I'll keep digging into the harness to see if I find anything else that may be a diode. I will pull the cowling off the engine to get a better look at the engine harness. I did run electricity through the unit I suspect of being a diode in both directions and I know that's not supposed to work (but I'm not even sure it is a diode). If I don't uncover anything, I will get the model number from the engine, as I assume the charging system is more a part of the engine than a part of the tractor.

 

[paulr44]

To add to 30yr's good answer, White is an MTD brand. You can look up parts etc. here:
http://mtdparts.arinet.com/scripts/...=Empartweb&loginID=mtddealer&Loginpwd=6922941

 

[Don L]

The White LT1650 IPL lists a TVT691 or VtX691 engine using a P.N.611184 16 amp regulator which is no longer available through some suppliers.
To test the regulator check the dc output at the regulator(red wire),if not at least 12 volts dc check the ac output at the two wires from the alternator. Sorry I don't remember the exact voltage,I think around 20 volts should be good.
To test regulator:Set multimeter to dc voltage,disconnect output wire (single wire,usually red)and connect positive test lead.Ground negative test lead to engine block.Start and run engine at full throttle and take reading.
To test alternator:Set multimeter to ac voltage,disconnect alternator wires from regulator,connect both test leads to the alternator connector,run engine at full throttle and take reading.
Maybe someone else can supply more accurate specs but I thought this might be helpful.
Don

 

[paulr44]

Any typical regulated system on OPE engines has 2 leads coming from the stator under the flywheel. Since almost all systems utilize half-wave rectification, you need to see at least 28 (up to 50 is ok) VAC from the stator at full RPM (with the stator isolated from the regulator). As it's half-wave (as in sine wave), cutting the AC output in half gives you about 14 VDC from the regulator.

Static test battery should be about 13.2 VDC (2.2 volts per cell), with engine running battery voltage should increase, and when a load is applied such as electric clutch or headlights, voltage at battery should remain between 13.2 and 14.7.

Testing the battery first is a must. Another check is to ensure that with the keyswitch on (older units anyway, newer need not be on many units) that you see battery voltage at the center or output terminal on the regulator. The batt. can't be recharged if the regulator is out of contact with it. Dirty connections can be an issue too, especially corrosion. One of my motorcycles boiled the battery dry from a regulator with a corroded ground - the high resistance fools the regulator into thinking it isn't sending enough current so it sends more.