Swallow, I certainly hope not, I'll be in a world of pain trying to fix that!!!
Cheers pkr, my 5.5mm socket arrived today so did some testing (new speed controller tomorrow hopefully)
Disconnect, if you can, the plug with the two thick wires. The fan should stop. If it doesn't, the fan is finding an earth that it shouldn't! In all probability, the fan will stop.
RESULT = Fan stops
Reconnect the plug with the two thick wires and check the fan is now running again. Now disconnect the plug with the three thin wires -
If the fan continues to run, you have a fault with the speed controller.
RESULT = Fan runs
So looks to be the speed controller, I removed the controller, took the lid off, but everything appears okay, no signs of anything that's blown. Is there a simple test I can do to verify it's knackered, i.e. measure continuity between two points.... I'm kind of just interested in understanding the testing theory.
Also a basic question, I'm struggling to comprehend the switched earth connection at the fan. I think I understand the concept of volts, current and resistance. So at the fan end, I took some measurements to try to understand what was happening....
VOLTAGES: (measured with multimeter -ve probe earthed, +ve probe on connector terminal)
FAN ON, Pink cable - 12.4V, Orange - 0V
FAN OFF, Pink cable - 12.4V, Orange - 0V
CURRENT: didn't measure as I believe may blow my multimeter fuse (rated at 20A)
RESISTANCE: (measured with multimeter -ve probe earthed, +ve probe on connector terminal - maybe this is actually a continuity test?)
FAN ON, Pink cable - 0 Ohm, Orange - 0 Ohm
FAN OFF Pink cable - 0 Ohm, Orange - O.L (I think this means infinity)
So if I understand this correctly the resistance (continuity?) tests are showing the switched earth, as in when the fan is on the speed controller is providing an earth/ground to the fan. When the fan is off there is no earth/ground (in this case I'd pulled the two thick cables so I think I had removed the speed controller earth/ground, normally a working speed controller would provide this when set to Zero on the dial)
Does the above make sense or are my basics wrong?