County AC Fan Speed

[manic]

Can someone help me figure out the county Aircon blower.

I've got the MUC1663 blower unit
http://www.aulro.com/afvb/projects-tutorials/163334-adding-air-con-bulkhead-install-td-tdi.html

My defender blower control switch has three speed settings that leads to a three pin power plug

Pin 1 12v
Pin 2 Ground
Pin 3 Ground

Switch Positions:
Low = Pin 1 12v , Pin 2 Dead, Pin3 Dead.
Medium = Pin 1 12v, Pin 2 Ground, Pin 3 Dead
High = Pin 1 12v, Pin 2 Dead, Pin 3 Ground

So the regulator for defender heater fan must have been inside the unit, switched about by the status of the power pins.

On the MUC1663 unit there are only two leads 12v and Ground. I can only give it 12 volts with my switch, so fully on or off.

Did this county unit have selectable fan speed? If so how did it work, did the county fan select switch output 4v, 6v, 12v or something?

[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)

[manic]

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.

https://www.aulro.com/afvb/images/imported/2013/02/1169.jpg

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 :o

[manic]

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!

[goingbush]

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

https://www.aulro.com/afvb/images/imported/2013/02/1159.jpg

https://www.aulro.com/afvb/images/imported/2013/02/1160.jpg

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

[manic]

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

[goingbush]

this will work

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

https://www.aulro.com/afvb/images/imported/2013/02/1157.jpg

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.

[manic]

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.

[goingbush]

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?

[manic]

Oh one other thing. Does the MUC blower pull more amps than then defender blower? I don't have the defender blower anymore so I cant test.

Just wondering if the existing 12v heater feed on the loom is beefy enough. The MUC power cables look quite a bit thicker than the 12v heater supply cable on the loom.

I did a test run with it positioned on the bulkhead and it didn't blow a fuse running on full. So that's a good start :). With the MUC on full and all but a couple of small air leaks still to address it blew a decent stream of air into the cabin. It runs a lot smoother and quieter than my defender fan so I suspected the air in cabin to be pretty weak but its just as good. So about the same air throughput with less noise.. nice!

[manic]

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?

Ok if you don't mind sending it then I'll take it, I didnt want to take up your time unless I was 100% sure I'm going to use it. If you send me your paypal and postage cost I'll re-reimburse you.

There are three pins from the fan switch. When the switch is in the off position there is 0v on pin 1. On the high, medium and low positions pin 1 will be 12v, pins two and three are grounded depending on medium or high setting selected.

[Stu82]

Hey guys,

I was reading this thread with a lot of interest as I had just taken my unit out of my '86 MoD Defender 110 for refurbishing. The inefficiency of the resistor is bothering me.. :mad:


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.

If I'm correct (not sure though) the speed of the motor is controlled by the amount of voltage it gets? In that case wouldn't it make much more sense to use a buck down (step-down) converter??

There are these cheap 10A usually around 0-30V converters from China...

Added benefit is a finer control of the blower, but ofcourse one would probably migrate from that 2-position slider to a knob or something.

By the way, does anyone know if the motor has brushes, or is brushless (if that even matters)..

Thanks guys!