Thread: County AC Fan Speed

Most A/C & Heater Fans including Td5 & Tdi , and I would also think County
use a 3 or 4 position switch and a ceramic or open wire wound resistor, which is recessed into the airflow, The resistor gets VERY hot & if it wasnt in the airflow it would burn out.

On High the 12v goes direct to the fan motor, on low the 12v goes thru the resistor then to the fan motor (not efficient but it works)

I have a spare Td5 dual resistor if you want it (free)

oh not to worry, I think I found the bit that does the voltage switching for the defender blower. Part UTP1281 - hidden away inside the heater box.



The two pin plug must feed volts to the fan.. so I suppose if I find one of these I can seal it in a waterproof case, stick it on the outside of the MUC , plug the two pin to the MUC fan and the three pin to original harness for three speed fan control.

Shame its £80 new

Originally Posted by goingbush

Most A/C & Heater Fans including Td5 & Tdi , and I would also think County
use a 3 or 4 position switch and a ceramic or open wire wound resistor, which is recessed into the airflow, The resistor gets VERY hot & if it wasnt in the airflow it would burn out.

On High the 12v goes direct to the fan motor, on low the 12v goes thru the resistor then to the fan motor (not efficient but it works)

I have a spare Td5 dual resistor if you want it (free)

Ah thanks yes I wouldn't have thought of that - it must be in airflow ey... hmmm I suppose I could place it in the vent/funnel then.

So the TD5 resistor spare that you have, is it the part I posted above? That would be super!

Td5 resistor is different, It has to go into the fan housing so the fan directly cools it, you need to cut a hole in the housing to suit.

PM your address, will stick it in the mail tomorrow





Alternatively you can get an electronic speed controler from Jaycar etc & have infinitely variable fan speed.

Thanks! Placing that resistor into the air flow wont be a problem, but how do you wire the pins?

this will work

dont forget to take the 12v supply from a ignition On Relay , Fused 20A, not direct from ign supply,



You need to be able to understand this diagram, if you do you will understand why the A/C only works on HIGH when the resistor is blown,

you are still going to measure 12v with a multimeter coming out of the resistor, as a multimeter has no load, once you load the circuit with enough current (eg, attach the fan motor) you will see a voltage drop across the resistor. A lot of current gets chewed up by that little resistor which is why they burn out if the motor jams up or the airflow over the coil stops. Ditto - Electronic speed control, they use a thyristor / triac or similar mounted on a heatsink, which is why you burn your finger if you touch the heat sink.

obviously its all more efficient with the fan on high, seems stupid to introduce a red hot resistor into the air flow that your then going to try and cool down with the evaporator.

Wow thanks that diagram is super helpful, completely understood. There is still one issue to solve then. My fan switch provides a constant 12v on all settings and earths one of two pins if on medium or high. So I guess would need three relays, two negative trigger normally off and one negative trigger normally on so that:

- given just the 12v it will run through the 2 ohm resistor
- activate the medium earth pin and it will open the 1 ohm and close the 2 ohm
- activate the high earth pin and only direct line is open.

Hmm I will consider this but it would be a cleaner install if I could get hold of the UTP1281 part that would just plug into the existing loom without need for relays or new wiring.

Before I trouble you with postage, I'll need to decide exactly how I'm going to do it. I may be able to find UTP1281 for cheaper than the bits required to hook the TD5 resistor up. I'm in no rush so I'll see what I can pull together over the coming weeks, and get back to you about the TD5 resistor if it turns out to be the best option.

Thanks a lot for your help. Much appreciated.

Manic, its going in the bin, you better take it even if you don't end up using it. Might just have a few weeks as we are all but packed and about to hit the road for 12 months, I've already packed the old loom that plugs into that, in the shipping container for storage, its buried in a bit far to retrieve.

do you have 12v on all your switch contacts, all the time, or just when the switch is pointing to that contact?