Technical Heater blower only operating on high speed setting

[capers626]

Hi all,

I have a query about the heater blower on a 1993 Fiat Uno Mk2 999cc (L reg) as it is only operating on the high speed setting and intermittently when it does spring into life (three speeds available normally). It sometimes makes a whirring noise in cold weather which suggests the motor is on the way out due to age.

After doing some research, which may or may not be relevant to an Uno, it seems that when the blower fan is switched onto high speed the circuit is a straight connection from positive to negative battery power but at lower speeds electrical power is typically routed through a series of resistors or a solid state speed controller assembly that drops the voltage down, which in turn makes the blower motor turn slower.

I am not aware of a separate resistor outside the motor housing unless it is built in internally, which wouldn't make a lot of sense if it needed to be replaced? Alternatively the plastic switch control outside the casing behind the front fascia plate may have a part which does the same thing?
Is there a resistor located near to the heater casing in a more accessible location?

Can't see any mention of a resistor when looking at the layout on the Fiat ePER, unless missed.

Any thoughts or advice appreciated.

Cheers,
Andy

 

[bugsymike]

Hi all,

I have a query about the heater blower on a 1993 Fiat Uno Mk2 999cc (L reg) as it is only operating on the high speed setting and intermittently when it does spring into life (three speeds available normally). It sometimes makes a whirring noise in cold weather which suggests the motor is on the way out due to age.

After doing some research, which may or may not be relevant to an Uno, it seems that when the blower fan is switched onto high speed the circuit is a straight connection from positive to negative battery power but at lower speeds electrical power is typically routed through a series of resistors or a solid state speed controller assembly that drops the voltage down, which in turn makes the blower motor turn slower.

I am not aware of a separate resistor outside the motor housing unless it is built in internally, which wouldn't make a lot of sense if it needed to be replaced? Alternatively the plastic switch control outside the casing behind the front fascia plate may have a part which does the same thing?
Is there a resistor located near to the heater casing in a more accessible location?

Can't see any mention of a resistor when looking at the layout on the Fiat ePER, unless missed.

Any thoughts or advice appreciated.

Cheers,
Andy

May look like this and possibly on side of fan motor body.
Re slow fan and often after lack of use I have sprayed WD40 directly into fan inlet ducting and it has freed it off, OK if you can ignore the smell of WD40 for a while.

 

[capers626]

Hi Mike,

Thanks for the info. Is the image you've attached taken from a heater unit for an Uno Mk1 rather than Mk2? I can't see any wires/plugs/sockets on the casing for mine. Just the plug (4 wires) coming out of the motor.

Do you know if the spin speed is governed solely by the settings on the plastic switch control (two or three) outside the casing behind the front fascia plate? Or in combination with the internal windings/design of the motor itself? The switch control may be sticking or have developed a fault.

I can try the WD40 tip, would this mean removing the unit or just a case of squeezing behind to get access to the inlet ducting!

Cheers,
Andy

 

[bugsymike]

Hi Mike,

Thanks for the info. Is the image you've attached taken from a heater unit for an Uno Mk1 rather than Mk2? I can't see any wires/plugs/sockets on the casing for mine.

Do you know if the spin speed is governed solely by the settings on the plastic switch control (two or three) outside the casing behind the front fascia plate? Or in combination with the internal windings/design of the motor itself? The switch control may be sticking or have developed a fault.

I can try the WD40 tip, would this mean removing the unit or just a case of squeezing behind to get access to the inlet ducting!

Cheers,
Andy

I did the search online saying Mk2, but check yourself.
Many Fiats use a resister on the fan body which helps get rid of the heat from resisters and use several wires from switch to give different speeds via resister, not aware of separate motor windings on motor it's self on those.
Some people have had wiring connectors overheating causing issues so worth checking for damage.
Where I used WD40 I just pulled back the ducting and sprayed into the fan motor in situ. Usually where fan motor reluctant to spin up and noisy from lack of use. Really just another area to try/check.