TR 70 motor problem

[homesteader1954]

Hi..went to start the 390 gas motor today and it started right off then quit .upon investigation I see smoke rising when the key is on from a resistor block before the coil . So power goes to the resistor block ... through it and out to the coil. That restore got so hot it was smoking.
On all the gas ford vehicles I ever owned I never saw this resistor except on dodges.
Why is it there?? And can I remove it...or is this a warning there is a problem in another spot in the ignition.?

 

[Mtnfarmer]

Not familiar with combines but if your resistor is a ceramic block looking thing engine should be a 391 Very common in industrial -truck and farm equip applications just replace it and you should be fine we go the same thing every year with two of our older ford silage trucks

 

[Bob]

Resistors limit current and reduce/"drop" voltage by converting electricity into heat.

That's what they do, it's their job!

Likely, it's always operated that hot, you probably just noticed now because it hot some oil on it making smoke.

Basically, your machine has a 6 Volt coil, and the resistor is "dropping" about half of the 12 Volt (nominal) battery voltage, limiting current through the coil's primary to somewhere in the 3 to 4 Amp range, preventing overheating of the coil, and short breaker point life/"burning" of the points, which is what's gonna happen if you remove the resistor.

Likely, the resistor is bypassed during cranking, keeping ignition voltage up while the battery voltage is drawn down by the starter load.

That's why some 12 Volt machines use a 6 Volt coil, instead of a "true" 12 Volt coil that doesn't require a resistor.

As a side note, if breaker point gap is excessively WIDE the points stay closed longer between sparks, INCREASING dwell and making the resistor and coil run hotter.

 

[SVcummins]

They get hot and eventually burn up just replace it and you?ll be good to go again .