Technical Fan burning out fuse

[NickHill]

I have a 2.8td fiat engine (Year 2000) in my Hymer Ducato motorhome.
The fan heater keeps melting the fuse when on full for a length of time.
The switch seems to work fine in all positions, the regulator seems to work fine as it draws 4 8 12 16 amps in positions 1-4. I figured maybe a bad connection on the fuse box so bypassed this but still kept a 30 amp fuse in line. No difference so I took the fan motor out and had it checked at my local motor rewinding company, they said that the motor is fine.
So now I am out of ideas, on full power the amp readings just climb slowly until the fuse burns, it doesn't blow as such just melts.
Any help could save my sanity.
I have a motor on it with a part number 591920600 I believe that this may be for a non air conditioned vehicle, mine does have air con.
Fiat gave me the part number as 71734232 and said this is a new number, it used to be 46722702 neither of which match what I have.
Could this be the problem? what would the difference be between the motors? does the aircon draw more amps. I have only recently bought the vehicle so am not sure that this hasn't been a problem since this motor was fitted. A new motor is £191 so don't want to buy unless I am sure that the motor is the problem.:bang:

 

[Crossingkeeper]

The fan heater keeps melting the fuse when on full for a length of time.

On my van (2006 2.8JTD) there is a heater switch position (furtherest clockwise) for a heater element; I rarely use this but always assumed that this element is located somewhere in the fan ducting and is intended for use when the engine is cold.

Perhaps this is coming on all the time (faulty rotary switch?) and drawing the excess current. No idea where it is located but the supply should be routed through the rotary heater switch so could be disconnected there as a check.

Otherwise it may be the fan speed regulator resistance bank at fault (breaking down as it warms up) From what little I know about electric motors, if it was faulty the fuse would blow immediately, so I would be looking elsewhere than the fan motor.

 

[NickHill]

Thanks for that, i believe that mine has some kind of symbol on the highest setting which i think is a demist screen type symbol. i certainly need it on the highest setting to stand a chance of demisting such a big screen.
Your comment on the regulator is a good one, it could be breaking down and drawing more ams as it gets hotter. Being the cheapest part in the circuit i think that i will start with replacing that. Many thanks for your advice, i will post back and let you know how that goes.

 

[adlarplant]

hi ive got a 2011 model and have all sorts of problems with the fan switch burning out wiring issues etc. Found switch hot to touch when in use even had the wires catch fire through resistance in the switch finished putting relays on every wire from the switch to the fan resistor ie.every fan speed to take the load off of the fan speed switch just like wiring up driving lights switch now carries minimal load and runs cool to the touch and no more fan swith problems cheers Adam

 

[NickHill]

Thanks Adlarplant, I'm not sure that I have the electrical knowledge to attempt that myself. I did bite the bullet and buy a new resistor/regulator but unfortunately to no avail, £60 spent and being a special order part, no chance of taking it back for a refund. I am thinking that the switch should be the next part in the circuit to change being cheaper than the fan motor itself. I just wish I had some confidence that it may solve the problem.

 

[NickHill]

I'm afraid to say that I never did get to the bottom of this and was never able to use the fan on full blast, have now sold the vehicle.