Allis D-17 Electrical Issues

Working on restoring my grandpa's 1964 Allis D-17 Series IV Diesel tractor. We've had it through the shop to fix leaks and what not. At that time, they put a new voltage regulator and generator. We brought it home and dis-assembled it to get ready for blast and paint. After sand blasting and painting, we started re-assembly. The other day we went to hook up the battery and it sparked quite a bit and then a "sizzle" sound and we fried the main wiring harness. I figured the wires may have been brittle and maybe got hit a little with sand which made them bare and caused a short. Yesterday we installed a whole new wiring harness. Still no luck. Battery would still spark when trying to hook up the second terminal, which shouldn't happen. I'm very confused as to why this is happening. We found that the heater solenoid was getting power with the key off, so I installed the old key switch, hooked up battery, but tractor still would not start. I've also installed all new gauges for this tractor which are currently on in, not sure if there could be a problem there or something? This tractor is 12V positive ground with a generator and voltage regulator. Any help would be appreciated to try and get this thing running again! Thanks!

they are positive ground if they have a generator check if you use two battery's instead of one they are hooked properly in series

Edited by polarbear - 14 Apr 2019 at 3:07pm

we just have one 12V battery on the tractor.

This is where it pays to buy quality parts. If you use high quality battery cables it is very difficult to hook the battery up wrong. The positive stud on a battery is larger than the negative stud. Quality cables take this into account and the battery cable terminals are sized for this. Cheap cables are made to fit either way. Try to fit the cables backward on a newer car and you'll not be able to tighten the positive cable on the negative stud. Also you'll not be able to even put the negative terminal on the positive stud unless you open it way up. I can't even open the negative terminal wide enough on my newer Ford. I just replaced that battery and I was barely able to put the negative terminal on the negative stud. Not that I'm wild about how it is designed in other ways.

Probably cooked the voltage regulator if you hooked something up wrong or backwards, and no way of rewiring will fix it. You can remove the cover and see if any contacts are stuck together.
 If you do get it wired up like you think it should be, don't crank the engine over till you flash the generator. There's no telling which way it will want to charge, if it does, and could make more of a mess than you have already.

https://www.youtube.com/watch?v=7VI4senn3PE

Edited by HoughMade - 15 Apr 2019 at 10:35am

Only electric gauge in the dash cluster is the "ammeter". 

Edited by schroeder.389 - 15 Apr 2019 at 10:52am

Hey guys, thanks for all the tips!  Had another set of eyes on this tractor last night and we identified two wires wrong on the key switch.  We also had a bad solenoid (even one of the new ones was bad that we had put on).  We had constant power to the heater, and needed to get that resolved!  We hooked everything back up, put some fuel and, and got the tractor running last night!  Such a good feeling!  Thanks for all the help!

Fundamentally there are several changes to be made when changing from positive ground electrical system to negative ground. While a positive ground alternator is theoretically possible easily virtually none exist because ever since 1964 or so SAE standards require only negative ground. Tractor makers were slow to follow that standard.

The ammeter connections need to be swapped so it reads right. Should show discharge with the engine not running and the lights on. Must show charge with the engine just started and the generator or alternator charging the battery. Some electric gauges for cooling system temperature and for fuel do not tolerate polarity change so have to be replaced with negative ground gauges and senders. If gasoline burning the ignition coil primary connections need to be swapped. Normally the primary connections are marked by a + and a -. For positive ground power goes to the - terminal and the + terminal goes to the points. For negative ground power goes to the + terminal and the - terminal goes to the points. Reversed coil connections won't absolutely prevent the engine starting but won't have a good spark for high speeds of heavy loads compared to the correct connections.

If the polarity change is accompanied by a change from 6 volts to 12 volts, gauges need to be replaced and the coil needs to either have a series resistor added to the power connection or changed to a 12 volt coil. 12 volt coils can have more primary turns or be a lower voltage coil with a suitable resistor inside the coil casing to make it work best at 12 volts.

If changing to a modern alternator the ammeter may need to be replaced with one having a current full scale at least as great as the alternator current rating.

Gerald J.