Fan speed doesn't work

[Shearer]

The fan speed on my VY doesn't work at all, so far I've checked: fuses, relays and wiring plugs and nothings appears out of the ordinary.

Does anyone have any ideas what could be the problem?

[spauldj308]

In my VR, there is a unit under the cowl panel (under the windscreen) that controlled the dwell of the fan speed motor. That's probably the problem

[Shearer]

I replaced the fan resistor in my VN as speed 1 and 2 fail, quite possible the VY ones has packed a sad too

[Sabbath']

Both likely correct. Fan speed resistor sounds like it's cactus.

[wortus]

The resistor pack would be bypassed on full speed operation. As it's not working at all I'd check the fan motor, see if you can disconnect it and put 12V directly onto it and see if it runs.
You could remove the fan speed resistor and check the wiring there for power etc at the various settings, your going to have to get a voltmeter or test light and work your way from one end of the circuit to the other.

[Shearer]

Funny enough there is no power at the fan resistor, yet when I use a multi-meter on the plug and alter the fan speed, I can see the voltage alter on certain speeds.

Is the fan wiring simple enough: ei: the circuit doesn't pass through the BCM?

[wortus]

I've got a wiring diagram here and the fan circuit does not go through the BCM except for the GR-Y wire that runs between the fan speed switch and resistor pack. I think it ma just be a signal wire to the BCM that the fan is running so the AC can work given that it is no th elowest speed turning the switch to any speed woudl send an earth signal to the BCM as would turning the fan off as you have to go past the slowest speed to turn it off? I'm only mnaking an educated guess here as to what it is for and how it works though.

[wortus]

Looking at the wiring diagram further I think this is how it works. There is a fan relay and this would close for the fan to run at full speed. It is controlled by the fan speed switch and actuates when full speed is selected. When a lower speed is selected this relay would be open and the current would flow through the selected resistor providing 3 different voltages at the fan motor for each speed selected (1 to 3) due to it's load causing a different voltage drop over each of these resistors. These are the different voltages you are seeing. There is a fan inhibit relay that stops the fan altogether if the igniotion is turned off and the fan speed switch earthes through it's normally open contact.

The curcuit is as such, +12 volts to the fan motor, the earth side of the fan motor goes to the resistor pack/fan relay when then goes to the fan speed control switch to the fan inhibit relay then to earth. One wire between the resistor pack and the switch goes to the BCM probably a signal wire to that module for some reason? It's the GR-Y wire (green/yellow I suspect).
The fan speed switch, resistor pack and both relays operate in the earth side of the circuit ie between the motor and earth. So you will see 3 different voltages on the wires from the resistor pack to the fan speed switch as you have. This means the motor is not burnt out or open circuit in theory if you were to earth any of the wires corresponding to speeds 1, 2 and 3 at the fan speed switch the fan should run. Initially I'd earth the other wire that runs from the fan inhibit relay to the fan speed switch which doesn't have a colour code on the diagram but I suspect may be black and see if the fan runs on all speeds (it should with or without the ignition turned on). If it doesn't run the fan motor may be siezed, if it does the fan inhibit relay is probably the culprit. The fan inhibit relay can then be removed and the connections corresponding to it's normally open contacts briged out and the relay bench tested. If these find no fault then check for voltage on the fan inhibit relay's coil when the ignition is on, if there is none you wil need to check power from the ignition.
I can PM you the wiring diagram if you like just let me know.

[Shearer]

I thought the switch and resistor work through an earth set-up.

I find out the problem, it was the fan (or spare parts refer it as the blower) was stuffed. I brought a new one and put it in, would you believe it only took half an hour to do. I initially thought it may have been a 'dash-out' job, thankfully it wasn't