cooling fan resistor

[bear-mg]

Can the cooling fan resistor be bypassed temporarily...reason I ask is a friend's 75's low speed isn't working due to failed resistor,I'm going to source a new one but as a temporary measure can I just bypass the old resistor with some cable?

[FrenchMike]

Can the cooling fan resistor be bypassed temporarily...reason I ask is a friend's 75's low speed isn't working due to failed resistor,I'm going to source a new one but as a temporary measure can I just bypass the old resistor with some cable?

Yes,you can ,the resistor is nealy a short circuit (0.47 ohms)

[bear-mg]

Cheers...that should mean with it bypassed at lower engine temps the high speed will work?

[FrenchMike]

Cheers...that should mean with it bypassed at lower engine temps the high speed will work?

Yes ,and bear in mind ,the current is fairly high :}

[andrewinpopayan]

FrenchMIke is absolutely right, the current is about 10 amps, so use a decent piece of wire. You could theoretically put a 55w headlight bulb in place of the resistor for now.

[FrenchMike]

FrenchMIke is absolutely right, the current is about 10 amps, so use a decent piece of wire. You could theoretically put a 55w headlight bulb in place of the resistor for now.

I think it's a bit more ;motor is given for 400 watts
so theoretically 400/12=33 Amp :shrug:

[andrewinpopayan]

I think it's a bit more ;motor is given for 400 watts
so theoretically 400/12=33 Amp :shrug:


I was working on the power dissipated in the resistor as I^2 x R = W

10^2 x 0.47 = 47 Watts. I think a headlight bulb would certainly slow it down. If it was a twin filament H4 type you could connect the filaments in series or parallel.

[FrenchMike]

I was working on the power dissipated in the resistor as I^2 x R = W

10^2 x 0.47 = 47 Watts. I think a headlight bulb would certainly slow it down. If it was a twin filament H4 type you could connect the filaments in series or parallel.

Correct ,Connecting the two filaments in parallel ,you get about 80watts
12^2 divided by 80 =1.8 ohms.

a bit high but it will run :}

[andrewinpopayan]

Correct ,Connecting the two filaments in parallel ,you get about 80watts
12^2 divided by 80 =1.8 ohms.

a bit high but it will run :}


I would say any resistor between 0.33 ohms and 0.68 ohms would suffice if it had 100W rating. I have a 0.47 ohm in mine and I have to stand close to the fan to hear it running.