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Mod | | | Forums66 Topics128,136 Posts1,056,425 Members48,441 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Jerry is not the only one who wonders why "GM chose to use voltage-dropping resistors of one type or another on millions of cars and trucks for a couple of decades". The webpage provides an Electronic Ignition Overview which includes the following facts/conjecture? BALLAST RESISTOR
In order to increase the coil voltage at startup some ignition designs incorporate a "ballast" resistor. The resistor is switched in and out of the supply voltage to the coil. Once running, the resistor is switched in place and the coil is actually getting less than 12volts. When the engine is started, the resistor is removed and the coil gets the full 12volts. This provides a much better spark at startup to compensate for reduced battery voltage drawn by the starter. When starting a cold engine, the plugs and the air are cold, the cylinder pressure is up, and the fuel / air mixture is poorly controlled. The oil is thick, the battery is cold and its voltage drops as much as 60% because of the high current drained by the starter motor." | | |
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