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Anyone Replace The Defogger Switch Resistor?

1.3K views 7 replies 3 participants last post by  Coppertop  
#1 ·
Can't read the markings on the resistor for my 70 defogger resistor. By searching I found a post on the Nova website where someone said they thought it was a 4.2 ohm value. In that same post another poster thought it should be 6-10 ohms. Radio shack has two resistors that might work, one is a 10 ohm 10 watt 5% wire wound resistor good to 70C degrees and 350v. The other is 8 ohm non-inductive 20 watt resistor. Any thoughts on these as replacements?
 
#2 ·
Steve,

I used to give these out to anyone that asked for one (I was adding them on to my electronics parts order every once in a while.). If I can find one (I think I gave them all away, it's yours).

They are 4 ohms at 5 watts. It's "sandbox" style resistor (a rectangular ceramic body "cooker" :) wirewound style).

When I was working w/ another member he indicated that the modern replacements I sent him--one lead was not long enough, but this is easily fixed by either soldering on a piece of wire, or jury rigging the hold down clamp assembly.

If only your "LO" speed doesn't work, 99.9% this resistor has burned open.

;)

Joe
 
#3 ·
Yes Joe, my resistor is toast. I ohm'd it out and it is open. As luck would have it both switches that I've got are bad, so I need two resistor. I can probably get them locally at an electronics supplies store. So I should ask them for a 4 ohm, 5 watt, wirewound, cooker resistor. Thanks for chiming in on this.

Since I've got your attention can I ask you if you know where to attach the ground wire for the defogger motor? It seems that no one knows where to attach it in the trunk.

Steve
 
#4 ·
Well first off Steve, don't ask for a "cooker" resistor, I just used that as slang, as a wirewound resistor is one that usually gets hot. That's why they have ceramic bodies and are filled with actual sand or synthetic materials so they don't catch on fire.

Now, what you can do (this won't be pretty or 1000 point show car correct) is go to radio shack and buy (2) of the 8 ohm 20 watt non-inductive resistors and wire them in parallel. This will yield 4 ohms. And since they're 20 watt, they'll more than handle the heat--probably never have to replace again in your lifetime. Since you have (2) switches, you'll need (4) of these 8 ohm resistors.

These are quite big though, so mounting will be a challenge, an actual 4 ohm 5 watt unit from an electronics supplier will fit the little mounting assembly apart of the switch (it's a metal clamp).

I will check my factory assembly manual for the mysterious ground location for the motor itself. Will let you know.