Radiator fan blowing fuse

[stocky88]

Had an issue when putting radiator fan in cabby, kept blowing 25amp fuse in relay box. finally realised I had swapped fans and was putting in the fan from the old blue 3 door I wrecked, so checked resistance and the motors were different ohms, even tho they physically looked the same. So cleaned up the original cabby one and stuck it in, worked ok with 15amp fuse, so just beware if you are having problems with fan blowing fuses there are different resistance motors, dont know why.
As far as i know they should be the same and run a 20amp fuse.

 

[bidderman1969]

hhhhhhmmmmmmmm, something to do with if it has or hasnt got air-con?

 

[stocky88]

Don't think so, I did notice the one that blew the fuse has a resistor up in one corner of the frame, but I am sure I never had that wired in when it was on the blue 3 door.
The Haines wiring diagram doesn't show the extra resistor in the circuit either.

 

[Chris H]

strange, fans should but eh same. Only difference is the connector plug on the early and later ones.

I think one of yours is breaking down internally and shorting thus the popped fuse.

 

[stocky88]

Could be Chris, I did give it a good hosing down so may be water in the motor, anyway all good now cheers.

 

[stocky88]

OK problem has returned, this time it is blowing 30 amp fuses, 1 out of 3 attempts, ok when the fan is running, just when the fan starts up it blows. might go up to 35 or 40 amp. ???? has anyone got their fan resistor wired in? would that make any difference?
In theory if you wire the resistor in series with the fan motor, it should draw less current? (OHMS law)??
The fan is free running with no bearing noises.

 

[stocky88]

Anyone have the resistor wired in?
OK done some resistance measurements and found, fan motor is 0.4 ohms, at 12.5 volts thats a current draw of 31.25 amps.
If I add the 0.3 Ohm resistor in series thats 0.7 ohms at 12.5volts which equals a current draw of 17.6 amps, which should be about right and a 20 amp fuse should be fine to use.
Current will actually be less as the wires themselves should have a bit of resistance as well.
going to try that and see.
Any comments apreciated.

 

[stocky88]

OK I think I have solved the problem now, wired in the fan resistor and now will start running even with a 15 amp fuse, so have stuck in a 20 Amp fuse for extra peice of mind.
Must have been all that extra wiring I ripped out from the air conditioning, they do funny things to the fan wiring when air con is in the car.
All good, thanks for all your help, Ha Ha.