763 charging wire melts !!!

[Jeffscarstrucks]

I have a friend whos machine melted the charging wire between the alternator and the starter with no obvious shorts or noise from the alternator. The machine is on his property some miles way and I have not seen it first hand. It also took the two small wires with it where they were close to the large wire and the machine stopped when this happened. He unhooked the battery (VERY quickly) and looked for other damage but there was none...no fire luckily. Unhooked the large wire from the starter, seperated the small wires and reconnected the battery. The machine started and ran with no noise from the alt (bearings OK should equall no short??) and drove back to the shop. I am trying to help with a long distance diagnosis so I will say thanks in advance. You all helped me get my old ASV up to speed and I really appreciate the help, JEFF P.S. Any tricks to access the alternator to remove it so that it can be bench checked?

 

[mechanikat]

you have a dead short to ground. courious how he started it with "all" the small wires removed. (from where the alternator? the starter solenoid? anyway the picture doesn't seem complete. is the alternator reconnected back into the system? care is needed here as many alternators need a load when spun or they will fry. a good multmeter will locate the problem and also determine if the alternator output is acceptable on DC mode and Ac mode will determine if diode(s) are weak with out removal of the unit. anyway I would try hard to find the problem before disassembly of the system so the problem doesn't repeat itself

 

[Jeffscarstrucks]

you have a dead short to ground. courious how he started it with "all" the small wires removed. (from where the alternator? the starter solenoid? anyway the picture doesn't seem complete. is the alternator reconnected back into the system? care is needed here as many alternators need a load when spun or they will fry. a good multmeter will locate the problem and also determine if the alternator output is acceptable on DC mode and Ac mode will determine if diode(s) are weak with out removal of the unit. anyway I would try hard to find the problem before disassembly of the system so the problem doesn't repeat itself

Thanks, I am trying to do this long distance and second hand as well. The smalls were the small alt wires. The problem is that there is no "obvious" short. I will be back with more details or a solution...JEFF

 

[mechanikat]

Thanks, I am trying to do this long distance and second hand as well. The smalls were the small alt wires. The problem is that there is no "obvious" short. I will be back with more details or a solution...JEFF

I checked the shop manual to clear my own thinking. You are aware that the red wire from the alternator to the starter solenoid is always "hot". all the way to the positive battery terminal. Having said that I think your problem is somewhere on that wire ibetween the alternator and the starter, if the rest of the heat damage appears to be secondary. If the machine started and ran, that pretty much eliminates starter/solenoid section, also the fuel shut-off solenoid. I would consider running a temperary wire from the Bat terminal on the alternator to the starter to see if it over heated. As mentioned before if the machine was ran with the alternator Bat terminal "open circuit" the alternator may already be shot. But if as you seem to imply the alternator was totally disconnected(all wires) then there likely was probably no damage incurred from that stand point.

 

[mechanikat]

I checked the shop manual to clear my own thinking. You are aware that the red wire from the alternator to the starter solenoid is always "hot". all the way to the positive battery terminal. Having said that I think your problem is somewhere on that wire ibetween the alternator and the starter, if the rest of the heat damage appears to be secondary. If the machine started and ran, that pretty much eliminates starter/solenoid section, also the fuel shut-off solenoid. I would consider running a temperary wire from the Bat terminal on the alternator to the starter to see if it over heated. As mentioned before if the machine was ran with the alternator Bat terminal "open circuit" the alternator may already be shot. But if as you seem to imply the alternator was totally disconnected(all wires) then there likely was probably no damage incurred from that stand point.

part 2 if you have access to a multimeter disconnect both ends of the alternator wire and ohm it out to ground. I didn't mention this earlier as I assumed that wire had melted to the point where it was probably grounded from the heat...

 

[Tazza]

part 2 if you have access to a multimeter disconnect both ends of the alternator wire and ohm it out to ground. I didn't mention this earlier as I assumed that wire had melted to the point where it was probably grounded from the heat...

If it melted from the starter RITE to the bolt on the alt its probably a short inside the alternator and not rubbing to the chassis. The wire from the alt to the starter should be rated at more than the alt can produce so it shouldn't melt if it was to scuff to ground, but from the battery to ground WOULD burn, does that make sense?. I guess there could be an internal short.... Its really hard to say without seeing it. As for easily removing it, on an east/west machine i don't think there is an easy way.....

 

[skidsteer.ca]

If it melted from the starter RITE to the bolt on the alt its probably a short inside the alternator and not rubbing to the chassis. The wire from the alt to the starter should be rated at more than the alt can produce so it shouldn't melt if it was to scuff to ground, but from the battery to ground WOULD burn, does that make sense?. I guess there could be an internal short.... Its really hard to say without seeing it. As for easily removing it, on an east/west machine i don't think there is an easy way.....

A altenator can draw alot of curent when the diodes go bad. The main power wire should stand this, but perhaps if it was marginal. btw a 60 amp delco 1 wire bolts right up,
Ken

 

[Jeffscarstrucks]

A altenator can draw alot of curent when the diodes go bad. The main power wire should stand this, but perhaps if it was marginal. btw a 60 amp delco 1 wire bolts right up,
Ken

Thanks Guys, I am leaning toward the internally shorted alternator based on the info given to me. I will pass this on and see how it goes. I wish I had the unit in front of me! I did not know the path of the alt to starter to battery wire so that will help a lot. Thanks again and I will update on monday. JEFF

 

[Jeffscarstrucks]

Thanks Guys, I am leaning toward the internally shorted alternator based on the info given to me. I will pass this on and see how it goes. I wish I had the unit in front of me! I did not know the path of the alt to starter to battery wire so that will help a lot. Thanks again and I will update on monday. JEFF

As it turns out the main charging wire was shorted to ground. He was able to find it in a hard to see/access area. Now the hard part...any good advice on how to remove/install the alt on this machine. It was not charging (using a volt meter) after the offending short was repaired so I am thinking that an alt check is in order. Once again,I am the messenger on this long distance project so any help is really appreciated. JEFF

 

[Fishfiles]

As it turns out the main charging wire was shorted to ground. He was able to find it in a hard to see/access area. Now the hard part...any good advice on how to remove/install the alt on this machine. It was not charging (using a volt meter) after the offending short was repaired so I am thinking that an alt check is in order. Once again,I am the messenger on this long distance project so any help is really appreciated. JEFF

I seen this before where the large power wire from the starter to the alternator rubs thru the insulation at the fuel filter bracket ----

 

[Tazza]

As it turns out the main charging wire was shorted to ground. He was able to find it in a hard to see/access area. Now the hard part...any good advice on how to remove/install the alt on this machine. It was not charging (using a volt meter) after the offending short was repaired so I am thinking that an alt check is in order. Once again,I am the messenger on this long distance project so any help is really appreciated. JEFF

Sad to say i don't think there is an *easy* way to remove the alt...... Its in a horrible spot!!!!

 

[skidsteer.ca]

Sad to say i don't think there is an *easy* way to remove the alt...... Its in a horrible spot!!!!

One you roll the cab back, its not easy but its not that bad either. Take a piece of plywood and put it under you and slide in head first. A helper that know wrenches is asset and can help line the belt back up. Think I used a ratchet strap (gently) to hold tension on the belt, for the final tightening.
Now go find a Delco, and pitch that Mondo in the scrap pile. Also on my 853 I had to install a diode in one small wire when I did this conversion as it backfed power to the injection pump and the engine would not shut off until I put the diode in to only let current go to the alternator. Your case may be different and a 1 wire self exciting alternator would solve that problem.
Ken

 

[Skiddy]

One you roll the cab back, its not easy but its not that bad either. Take a piece of plywood and put it under you and slide in head first. A helper that know wrenches is asset and can help line the belt back up. Think I used a ratchet strap (gently) to hold tension on the belt, for the final tightening.
Now go find a Delco, and pitch that Mondo in the scrap pile. Also on my 853 I had to install a diode in one small wire when I did this conversion as it backfed power to the injection pump and the engine would not shut off until I put the diode in to only let current go to the alternator. Your case may be different and a 1 wire self exciting alternator would solve that problem.
Ken

What Tazz said X2!

 

[mechanikat]

I really appreciate the follow up post on the problem! I am glad you were able come to a conclusion. Too often problems are posted on forums all over the web. Solutions are offered, then nothing is ever heard again. Again thanks!

 

[Jeffscarstrucks]

I really appreciate the follow up post on the problem! I am glad you were able come to a conclusion. Too often problems are posted on forums all over the web. Solutions are offered, then nothing is ever heard again. Again thanks!

Thanks again for the help and I know the machines' owner appreciates it as well. I will let you know the final outcome as weather and time availability will pace the work . I agree that too many folks show up on a forum and run with the info without checking in so the next guy might learn from the whole process, not just a guess. I am on the Millerwelds forum and antique Cat forums as well (mostly reading) and the same thing happens there. Oh well......, Thanks Again. JEFF