Ford V8 ignition resistor question

[Mike K]

Originally Posted by Lynn Eades

I doubt it will change from cold to hot. .

Resistors definately change value with temperature .. a known fact .

The small resistors up to 1 watt in rating you see on many boards are made from a carbon based material ..for higher power dissipation , they use wire wound resistors , these are typically a special kind of wire , wound on a ceramic or similar material . The wire used in those old home electric bar heaters or old style jug elements, has a cold resistance value , and a hot value .

The Ford coil resistors are dropping around 3 volts ..with 2 or 3 amps flowing through it all day .. 3X3 = 9 watts .. doesn't sound much but that small resistor has to handle all that power and it becomes very hot . The voltage regulators are set to about 7.2 or 3 Volts and the coils are rated at 4.5 Volts I think. Its designed for easy starting on those freezing winter mornings . As the starter motor turns over , its pulling massive amps and the battery voltage drops down to about half its resting state .

the best solution is to install a resistor with the same ohms value, but with a bigger wattage rating ..maybe a 20 watter ...this would run cooler and not restrict the current so much. I'd look for an old electric bar heater and salvage the wire from the bar ..find a big round ceramic former and wind a new resistor .

Mike

Mike