Electrical diagnoses

[Trz]

1950 8n front dist. 6v system . No start. Been through the distributor 3 times making sure everything is working properly, points adjusted to 15 , did all the continu tests (points open, points closed , coil off and finally coil on ,and everything checks out. Put it back on tractor still no start. Check battery.. 6.43v. check key switch, on position.. 6.43 on both sides of switch. Check resistor key on.. 6.43 on both sides of resistor. Check from battery ground to top of coil..6.43 with key on, drops to between 2.4 and 4.3 when I hit the starter. Run jumper from battery hot lead to top of coil and tractor starts and runs. I’m at a loss as to what to do next. What am I missing?

 

[old]

1950 8n front dist. 6v system . No start. Been through the distributor 3 times making sure everything is working properly, points adjusted to 15 , did all the continu tests (points open, points closed , coil off and finally coil on ,and everything checks out. Put it back on tractor still no start. Check battery.. 6.43v. check key switch, on position.. 6.43 on both sides of switch. Check resistor key on.. 6.43 on both sides of resistor. Check from battery ground to top of coil..6.43 with key on, drops to between 2.4 and 4.3 when I hit the starter. Run jumper from battery hot lead to top of coil and tractor starts and runs. I’m at a loss as to what to do next. What am I missing?

Both the switch and resister can be bad but yet show voltage since it takes almost no amps to make a VOM read voltage. Jump across one then if it doesn't start jump across the other one. If that still doesn't work run a wire from the coil side of the resister to the coil and it is starts the wire if bad

 

[Jim L WA]

You shouldn't see the same voltage on both sides of the resister. I'm thinking like Old said. Open wire between the resister and coil.

 

[old]

You shouldn't see the same voltage on both sides of the resister. I'm thinking like Old said. Open wire between the resister and coil.

If the points are open you will read full battery volts on both side of the resister due to being and open circuit. If closed yes voltage should be a lot lower

 

[Jim L WA]

If the points are open you will read full battery volts on both side of the resister due to being and open circuit. If closed yes voltage should be a lot lower

You're right, I should have thought of that.

 

[old]

You're right, I should have thought of that.

But there is a twist to that also that cause many problems that many don't seem to think about or understand. If the points are closed but you get battery voltage at those point then the points are bad

 

[Trz]

It’ll start if I jump across the resistor leads, does that mean the resistor is bad?

 

[old]

It’ll start if I jump across the resistor leads, does that mean the resistor is bad?

Most likely YES

 

[Mad Farmer]

But there is a twist to that also that cause many problems that many don't seem to think about or understand. If the points are closed but you get battery voltage at those point then the points are bad

Or there is a short

 

[Mad Farmer]

It’ll start if I jump across the resistor leads, does that mean the resistor is bad?

A jumper wire with alligator clips should be in your tool kit/box. Long enough to reach from battery to distributor.

 

[Jim L WA]

It’ll start if I jump across the resistor leads, does that mean the resistor is bad?

Interesting. If it was bad why are you seeing battery on both sides? I'm thinking bad or corroded connections at one or both of those resister terminals. What say Old?

 

[old]

Interesting. If it was bad why are you seeing battery on both sides? I'm thinking bad or corroded connections at one or both of those resister terminals. What say Old?

I've seen many times when something is bad but yet a VOM gives you the battery volts but yet not be able to pass the amps needed. When that happen it can be a nightmare trying to trace where the circuit is bad. Being a former Navy E.T. computer and then after the Navy a electronics repair person I've seen things like this way to many times

 

[Trz]

Interesting. If it was bad why are you seeing battery on both sides? I'm thinking bad or corroded connections at one or both of those resister terminals. What say Old?

I thought maybe bad connections too so I cleaned them earlier but it didn’t make a difference.

 

[old]

I thought maybe bad connections too so I cleaned them earlier but it didn’t make a difference.

Voltage does things that amps will not do. Or in other words you can have a bad part and see volts but when it comes to getting work done the amps aren't there to do the work. I've worked on electronics for over 50 years now and learned just because you can see volts it doesn't mean that the part is still a good part. An Example if that one singe strand of wire the size of a human hair can carry the volts that a VOM will read but if you try to make that wire power anything it will turn red and most likely burn out

 

[Jim L WA]

I've seen many times when something is bad but yet a VOM gives you the battery volts but yet not be able to pass the amps needed. When that happen it can be a nightmare trying to trace where the circuit is bad. Being a former Navy E.T. computer and then after the Navy a electronics repair person I've seen things like this way to many times

I totally agree, especially with starting circuits. I had 36 years in telephone central office switching and establishing and trouble shooting special services.

 

[ole fred]

Here's something that my father taught me about 65 years ago.

Imagine that and electric wire is like a garden hose with a nozzle on the end. Voltage is the pressure in the hose and amperage is the amount of water flowing out of the nozzle. If the nozzle is closed, you still have pressure/volts. When you open the nozzle and water flows, that is the gallons/minute- amps. Unless you have a heck of a source - a huge pump/huge battery - when you open the nozzle, the pressure/volts with drop. You still get water/amps out the nozzle though.

To me, this greatly simplifies the electrons that you can't see in the wire.

On another thing: An old timer - older than me - said to stick a coin between the two halves of the resister and twist it while you crank. This will shoot full battery voltage to the coil and make a hotter spark. The is pretty much what they did on the 12 volt ignition with the solenoid that shoots a full 12 volts to the coil while cranking.