Fan Speed Control: A Lesson in Resistance
There are a lot of misconceptions about how heater-fan controls work. There is but one truth. Heater-fan switches are not variable resisters. Resistance is the same in both (two-speed) or all three (three-speed) positions. Resistance comes from a resistor package installed in the heater plenum. The resister package consists of two lengths of resistor wire, which control resistance not to the fan motor but to ground. When the fan switch is in Low, resistance to ground is high, which impedes the flow of electricity to ground. This lowers fan speed. Move the switch to Medium and resistance to ground becomes less, raising fan speed. Move the fan switch to High and bypass the resistance wires completely, going directly to ground. The fan then runs at full speed.
This is a typical Mustang...
This is a typical Mustang three-speed fan switch. It is logical to assume it is a variable resistor because it offers three positions, but it is actually an electrical traffic cop that routes power to a variable resistor in the heater box.
Three wires route power from...
Three wires route power from the fan switch to the resistor package and fan motor. Power passes through the fan switch to the motor, then to the appropriate resistor to ground.
This is the variable resistance...
This is the variable resistance package, located on the heater box to aid resistor cooling.
LED Sequential Turn Signals
By now, most of you have seen Mustang Project's groovy LED taillights and parking lights for classic Mustangs. These easy-to-install lighting upgrades command more attention because they're brighter. What's more, they never burn out. Also, because they incorporate solid, reliable electronics, they will last virtually forever. Opt for the sequencing LEDs in back and LED bulbs in front. For more information, contact www.mustangproject.com.
No Unimportant Grounds
Grounding terminals exist throughout your Mustang's electrical system. All of them are important to proper electrical-system function. For best results, always ensure each of them is tied to the body/chassis as shown. Too many of us overlook the engine-to-firewall ground lead. Don't forget this one. If you do, expect all kinds of ignition and charging system woes.
Don't Cut That Wire!
We have seen all kinds of wiring molestation through the years, none of it pretty or necessary. Do you know how many sources for power there are in a classic Mustang? At least four that we can think of, which means you need never cut a wire to get power. There are also two triplex plugs for accessories and instrument lighting. All you need are bullet connectors to get power.
This is the instrument-lighting...
This is the instrument-lighting triplex plug for auxiliary lighting. Look for the yellow plug for auxiliary power to run accessories.
Power is available at the...
Power is available at the ignition switch from '65-'67.