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Cooling Fan blowing the fuse

seza

Nov 6, 2015
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Hi All,

I hope you clever people can help me with my problem,

On my car I changed the clutch fan with an electric one,
the fan is wired through a 40Amps Relay, everything works ok for a while
then the fuse just melts away! I used fuses as high as 30Amps!

The fan motor is ok, the relay has been changed twice, all wiring looks good,

what is causing the failure? how can I remedy the situation?

thanks for your help
 

Minder

Apr 24, 2015
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Have you tried running direct off of 12v and monitor the actual current?
M.
 

seza

Nov 6, 2015
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Thanks for your reply - Minder,
No I did not, I suppose I could hook the fan straight to battery,
to measure current, I could use clamp on multimeter? right?
 

davenn

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Sep 5, 2009
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I could use clamp on multimeter? right?


not sure if clamp meters work with DC ?


On my car I changed the clutch fan with an electric one,

out of personal curiosity ...... I really do not understand what you wrote ..... what the hell is a clutch fan ??

and if the fan wasn't electric before ... what was it ?
 

davenn

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I could use clamp on multimeter? right?

OK, so doing some reading ......

So how does a current clamp meter or current clamp accessory, which measures either ac or dc, work?
Two features allow such a current measuring device to measure either ac or dc. The first feature is to create an air gap in the magnetic circuit. The air gap limits the magnetic flux so that the core cannot saturate.
The second feature is a Hall Effect sensor, which is introduced into the air gap to measure the magnetic flux directly. The output voltage from the sensor is then amplified and scaled to represent the current flowing in a conductor placed in the jaws of the clamp.

You can generally tell the difference between the two types of clamps by inspection. The ac-only clamp will have bare metal core faces when you open the jaws, while the ac-dc clamp with a Hall Effect sensor will have the core ends covered by plastic jaw molding.


so @seza .... which type is the one you have ?
 

Tha fios agaibh

Aug 11, 2014
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out of personal curiosity ...... I really do not understand what you wrote ..... what the hell is a clutch fan ??

and if the fan wasn't electric before ... what was it ?
It's a viscous clutch assy that mechanically engages the fan when ambient temperature rises.
 

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seza

Nov 6, 2015
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not sure if clamp meters work with DC ?




out of personal curiosity ...... I really do not understand what you wrote ..... what the hell is a clutch fan ??

and if the fan wasn't electric before ... what was it ?

Clutch fan (viscous ) is a thermostatic device that due to temp changes can activate a "clutch" for the engine to drive the fan faster, it is fitted as standard on most large older engines such as trucks etc ...
(there you go I hope you learnt something new?)
 

seza

Nov 6, 2015
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Thanks for your input guys,
Indeed I do have a MMeter with AC-DC clamp, by connecting the fan straight to the battery the current draw was about 10amps! still not sure it is blowing the 30Amps fuse, I am going to change one of the wires that appear to be bit too thin, that might help.
 

Externet

Aug 24, 2009
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Connect your fan with the specified fuse, and when on, sense by hands which terminal/contact/splice to the fuse gets hot. If such hot point is near the fuse, it will conduct heat to the fuse causing it to melt before desired.
 

duke37

Jan 9, 2011
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I was asked to look at a combine harvester which was blowing fuses. The fault was hidden, worn through wire insulation, probably helped by a mouse. Shake, rattle and roll does not help.
Put a headlight bulb across the fuse connections to limit the current and give an indication of current.
I used the good filament of a faulty bulb, soldered across a blown fuse.
Depending on the fan it may even run when powered through the bulb.
Disconnect the fan and see if current still passes. If it does, replace the wire and find where it was rubbing.
Intermittent shorting can be very difficult to find.

Edit: Too thin a wire will reduce the current, not blow the fuse.
 

Minder

Apr 24, 2015
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not sure if clamp meters work with DC ?
The old moving coil clamp-on ammeters were AC only, the modern digital are generally AC/DC, mine is an attachment to my Fluke meter.
M.
 
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