I just about pulled the trigger on a delay wiper switch and corresponding black box thingy-ma-bobber when I started to think.

What slows the wiper motor down from high speed to low speed? Is it a resistor? On my '72 K20, the wipers are almost slow enough to not need delay. If I could just slow my Ford wipers down, I wouldn't need delay. Could I just add a resistor in low speed wire going to the motor?

I know I should just get the switch and box, but I like to tinker with things.

 

No delay for me.

Its all part of the experience of driving a 47 year old truck.

 

Would a resistor work? Or would it cook the motor?

 

Same thing applies with two speed wipers without intermittent wipers.

Turning the intermittent wiper switch **** to the left adjusts the interval, the time between one 'sweep.'

 

That's not what I meant (I'm not the best at putting ideas to words). What in the switch/motor lets the motor run at 2 different speeds?

 

Depends on the wiper motor as there were two used 1961/66. One is one speed, t'other is two speed.

 

The delay is a cheap and easy upgrade.
They work very well. The intermittent wiper switch doesn't seem to change the speed of the motor.
The switch turns the motor on and off in cyclic rates dependent upon where it is set in it's range of operation.

 

Years ago I had an early Bronco that had a vacuum wiper above the windsheild. Going up hills the engine loses vacuum and the wiper would quit. I found a replacement unit that was 6v so I swapped it in place of the vacuum unit. The wiper arm would sweep so fast, the wiper blade flew off the arm. I tried to haywire the blade to the arm, but it would keep flying off, but at least now the blade was still sort of attached and not gone forever.
I was young and still figuring things out, I asked my dad who is an electrical engineer about adding a resistor and he said that the way most dc motors are wound, they don't respond well to varying the speed. There are usually two sets of windings to get two speeds. AC motors, like a ceiling fan for example, can be slowed down with a potentiometer (dimmer switch) easily.
Afaik, there isn't a feasible way to slow the motor slower than the first speed. You either get a pulse/intermittent box, or go with vacuum wipers with a reservoir tank and a regulating valve!

 

i would think adding a resistor would change the speed of the wipe, rather than the interval between the wipes.

 

If I had a delay setup (which I now have), I wouldn't need to slow the wipers down. If I had a stock 2 speed wiper setup, a resistor would definitely slow the motor down. Would it be hard on the motor?

Where would the resistor need to be installed to make the high speed slower while leaving low speed alone, thus making high speed the new low speed?

 

It will harm the wiper motor eventually here is an Ohms law calculator use 12 volts 15 amps then increase I and see what happens to amps Ohm's Law Calculator
the more resistance you add the higher the amperage will go putting unnecessary strain on the wiring and the windings of the motor

 

So back to the original question: what did Ford use to vary the speed?

 

Also on the calculator thingy; resistors cut voltage only, correct?

 

They have two speed motors "two sets of winding in the case" I should have written "R" not "I". Yes resistors drop the voltage by consuming it and the byproduct of that is heat. Just a rule of thumb if you decrease voltage you increase amperage.

 

Just a thought if you also want to delay your high speed you could wire in a double throw single pole switch, with the wire from the delay relay to the common of the switch, low speed to one of the outside connections and high speed to the other connection on the switch. I do not know what amperage the delay is rated for so do this at your own risk.