New to the forum, so I appreciate any guidance. I am helping a family member repair the electrical system on their TO-30. It has a + ground, 12v system. When I first started working on this tractor, it was set up as a + ground. The entire wiring harness was deteriorated, so I have replaced it. New harness, resistor block, ignition switch, coil, points and condenser. I set up the battery with - ground, and the tractor would not start. No spark whatsoever. Switched back to + ground and the tractor started and ran beautifully. After turning it off (using the ignition switch), I started to smell an electrical odor. Found that the female blade insulation on one of the wires to the resistor block was melting (from the resistor block to the ampmeter), and the resistor block was extremely hot. I used glenmorebuckman's diagram (05-16-2021) as a guide, minus the #1 wire from the alternator to "I" on the keyswitch. The #2 wire from the alternator goes to one side of a resistor block (from TSC), and then from the other side of the resistor block to the amp meter. The coil (also from TSC) is a 6v, but states it can be used for 12v with an external resistor. Pretty sure I missed something pretty basic, but not seeing it.
- Thread starter ogreafmc
- Start date
old
Well-known Member
- Location
- Camdenton Missouri
A ballast resister will in fact get hot so hot it will burn your fingers if you touch it so normal
rvirgil_KS
Well-known Member
Does it have a positive or negative ground alternator? Most all common alternators were born negative ground but a few have been redone for positive ground.
If you switched polarity on the battery, even for a brief moment, you likely fried your alternator.
With positive ground the + post on coil goes to side of distributor. With negative ground the - side of the coil goes to distributor. On some tractors, with posts reversed they will be harder to start, but other than than the ground configuration should have no effect on starting.
Loose connections can cause heat build up.
If you switched polarity on the battery, even for a brief moment, you likely fried your alternator.
With positive ground the + post on coil goes to side of distributor. With negative ground the - side of the coil goes to distributor. On some tractors, with posts reversed they will be harder to start, but other than than the ground configuration should have no effect on starting.
Loose connections can cause heat build up.
Thank you for your input. I do not know whether the alternator is + or - ground. The owner suffers from Parkinson's and cannot provide much info for that. I have included a quick wiring diagram for what I originaly found, and it has been returned to this set up after replacing alot of coroded wiring.
Steve@Advance
Well-known Member
No, the diagram is not correct.
You can not reverse the polarity with an alternator! Unless it is a specialty
alternator set up for positive ground (99.9999% chance it is not), then it must
be wired for negative ground. Just for safety sake, check the battery to be
sure it is not charged backward, not likely, but it can happen.
Try this wiring diagram:
Conversion Wiring Diagram
You can not reverse the polarity with an alternator! Unless it is a specialty
alternator set up for positive ground (99.9999% chance it is not), then it must
be wired for negative ground. Just for safety sake, check the battery to be
sure it is not charged backward, not likely, but it can happen.
Try this wiring diagram:
Conversion Wiring Diagram
RCP
Well-known Member
- Location
- Grove City Pa
I do not understand the resistor on the lead from the alternator to the ammeter, could it be a
diode? Usually the resistor is the on lead from the ignition switch to the distributor to cut the
amperage and extend the life of the points.
You should first confirm that the alternator is positive ground, this is not normal so I would be
surprised if it is. If it is actually negative ground the system needs to rewired to negative
ground. Is the alternator actually a single wire alternator that does not require being energized
from the key switch?
Take a bunch of pictures of the tractor, the wiring, the alternator, ignition switch lugs etc and
post them, there are a bunch of smart people on here that are willing to help.
diode? Usually the resistor is the on lead from the ignition switch to the distributor to cut the
amperage and extend the life of the points.
You should first confirm that the alternator is positive ground, this is not normal so I would be
surprised if it is. If it is actually negative ground the system needs to rewired to negative
ground. Is the alternator actually a single wire alternator that does not require being energized
from the key switch?
Take a bunch of pictures of the tractor, the wiring, the alternator, ignition switch lugs etc and
post them, there are a bunch of smart people on here that are willing to help.
J.Wondergem
Well-known Member
- Location
- Rockford, Mi.
If that alternator is working, I can see why the resister burnt up.
While most generators were + positive ground, most alternators are the opposite - negative ground, so when an alternator is used to replace a generator the ground polarity of the entire wiring needs to be change to negative ground. When a negative ground alternator is hooked up in a positive ground circuit, the one way diodes in the alternator get fried. By your diagram, if the resistor is fried the diodes are likely fried too.
If the resistor in your circuit diagram is intended to be a ballast resistor to use a 6 volt coil in a 12 volt circuit, the resistor needs to be on the wire between the ignition switch and the coil.
If the resistor in your circuit diagram is intended to be a ballast resistor to use a 6 volt coil in a 12 volt circuit, the resistor needs to be on the wire between the ignition switch and the coil.
old
Well-known Member
- Location
- Camdenton Missouri
Resister should not be in line with the alternator output and amp gauge so that is why it gets so hot
Steve@Advance
Well-known Member
I agree JMOR, the alternator is probably still good thanks to the resistor.
The resistor may have taken a hit though!
The resistor may have taken a hit though!
There are enough things wrong , that rather than try to describe all the fixes, I recommend that you wire it as in this pictogram. Since your TO-30 uses stand alone coil , coil wiring will look more like the 8N diagram.
This post was edited by JMOR on 04/26/2022 at 08:55 am.
This post was edited by JMOR on 04/26/2022 at 08:55 am.
BarnyardEngineering
Well-known Member
- Location
- Rochester, NY
The coil is also polarity sensitive. If you had it wired up backwards for negative ground the spark may have been too weak for the engine to run. That's why switching the battery around made it run.
Unless you mean the engine would not even crank over with the starter. Then it had nothing to do with polarity and everything to do with bad connections at the battery. Swapping them around was enough to clean the connections so they would work.
This post was edited by BarnyardEngineering on 04/26/2022 at 11:34 am.
may have been" was a good choice of words. You will likely not ever know an answer. P.S., the coil output voltage will be reduced by one hundredth if polarity reversed, such as 9,900v versus 10,000v. HV polarity is different, but that matters not when cold. A slight bit when plug electrodes very hot, as electrons leave a hot surface a little easier the leaving a cold surface.
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