Alternator on a Model 76 getting hot, what am I missing

[gparobeck]

I have a Spirit of 76 (electric start) I am trying to bring back to life. When I first put a battery in it I noticed I had a ground spark when I hooked it up. There are no bare wires and the wiring appears correct when compared to the diagram. I pulled the fly wheel and discovered that the alternator was getting hot when the battery was hooked up. I figured it was a bad alternaator and replaced it. I have the same problem. The positive battery cable, the red wire to the keyed witch and the red and white wire are all on the same solenoid post. If I am reading the diagram correctly this is correct. What am I missing? Any Ideas?
Gary

 

[aschumacher]

Gary, dont really know this model Cub but...if you have an alternator, you have a heavy diode(s) somewhere to make DC power. If that shorts out battery power will go back into the alt, trying to make it a motor and cause it to overheat. Check it with an ohm meter..few hundered ohms one way and tens of thousands the other. Two readings close to each other equals a problem.

 

[gparobeck]

Allen, Thanks for the feed back. On the diagram they show a fuse in the line between the battery and the alternator. On the tractor is what looks like a fuseable link but there was no fuse in it. There is what looks like a black piece of plastic about 3/16" in diameter and 1/4" wrapped around the wire on one side of the link. It also has some white markings on it. Would this be the diode? And if so do they go bad?

 

[aschumacher]

Gary I really hope some of our electrical guys stop in here to help. Some diodes are marked with a band around one end to identify polarity. What you describe seems small to me to be a diode at a minimum of 15 amp capacity, but its possible. Also vibration is the enemy of many semi-conductor products, it may have fractured internally. Maybe Roland will help or Kraig has a picture that will help. A.

 

[aschumacher]

Gary go to the CubCadet Parts Lookup in the upper section by sponsors. Poke in 76 for the model and pick 76 in the list. Illustrated parts is where you want and then 'electrical+starting'. Item 10 and 15 are items of interest, and may give a better idea of location.

 

[kmcconaughey]

Gary, does your schematic match this one? Any diodes would be internal to the voltage regulator and not an inline setup. With the battery DISCONNECTED use an ohmmeter to measure from the battery cable connections to ground. Sounds to me like there might be a short somewhere.

 

[aschumacher]

Kraig/Gary, the parts image shows a single diode at the output of the alternator as well as a partial rectifier attached to the alternator. The schematic shows the battery connected directly to the alt. Only way to cook the alt is back thru the diode???

 

[kmcconaughey]

Allen, well look at that. I wonder why that doesn't show up in the schematic???

 

[aschumacher]

 

[gparobeck]

My thanks to all who replied. I am traveling all week and will check it with an Ohmmeter when I return and post the diagram I have. It isn't quite like the one Kraig sent. With regard to the parts catalog page. My alternator is the half ring type and has only one red wire coming out. The item I asked about this AM is item 15. I don't have anything that looks like item 10 unless it is internal.
Thanks again for the help I will be back Friday and jump back into it.

Gary

 

[gparobeck]

I think the problem is solved. I believe it was a bad diode. The alternator no longer gets hot and there is no spark when I hook up the battery. Now I need to get it all back together and get it started.

I want to thank all who replied. Your comments lead me in the right direction.

Gary

 

[kmcconaughey]

Gary, thanks for the update! Good to hear that you may have it solved. Kudos to Allen for pointing towards the diode.

 

[gfigurski]

I just picked up a little cadet 60 with a Tecumseh V60 70149g 6hp. The problem is the engine is missing the intake manifold, carburetor and air filter. Anyone have some ideas for a place to fine this stuff.I have ebayed with little luck. Thank you