The motor probably won't run without the capacitor, but I don't think that's the trouble because you said you got 240V on all three inputs when any one of the switches was pressed, and that wouldn't be the case if the motor was taking current, even if the capacitor was open-circuit.
Just when I thought that I nearly understood what was going on.
I thought that any one connection to the motor winding (red, blue, black) would show a voltage on all three connections because all three were connected to the same winding at different points.
This meant that if the red wire was connected to the purple wire by the switch then a voltage also appeared on the black wire via the winding which lit the neon (returning via the white wire).
I've replaced the capacitor and the motor still will not run.
I've looked up spares on line and the motor is about £140 (selected for this particular cooker hood) and there is a similar hood available via Appliance Direct for just under £100 delivered.
I've got to the stage of needing to split the motor body to gain any further access to diagnostics and although it looks doable I have no idea if this would reveal anything capable of being fixed.
I've only persevered this long because I was trying to learn how the damn thing worked (although a sudden inspirational fix would have been a major bonus).
Thanks for all your help (and also to others).
New hood delivered tomorrow with luck.
Cheers
Dave R
Depends a bit if all switch positions were tried and also on how precise the voltage reading was. I.e. not just the neon lighting?
Readings done with a digital multi-meter and all switches tried.
Although with my marked inability to draw and check a circuit diagram anything is possible.
However the upstream explanation of Dave W's circuit diagram suggests that whichever of the 3 switches is pressed, there is always a voltage on the black wire to the neon, because all three switches connect to different points on the same winding. Extending that logically there should always be a voltage on all 3 wires (not just the black and a.n.other) whichever switch is closed.
Every time I try and visualise it, though, I seem to get a slightly different result.
Cheers
Dave R
You said in your second posting that you got 240V on all three wires when any switch was pressed. The motor winding has 3 tappings and one common Neutral. When Live is applied to one of the tappings, by acting as an auto-transformer different voltages should appear on the other two tappings. But if no current is flowing because there is no connection to Neutral, all tappings will show the same voltage.
I assume it's not just a case of the motor shaft being gummed up, merely requiring some oil? I had to clean and oil my fan heater that would not go because of this only last week.
Wouldn't that then be symptomatic of a failed thermal fuse or base winding (depending on where it was in the circuit)?
You would still see the different voltages wouldn't you?
Our kitchen fan often takes a while to run up to speed when the bearings are a bit gummed up.
Cheers, T i m
O.K. - thanks.
That makes a lot of sense (I think).
The fan spins freely; one of the tests was to turn the fan on and spin the fan motor in case the capacitor was a start/run capacitor and it wouldn't get moving initially.
The one thing the bloody thing does have is lubrication; covered in the finest oil and fat that money can buy.
I will go and test it again just to confirm that all voltages are the same. AFAICR they were all just below 240V.
What I think I did was test between live and neutral and then confirm the same(ish) reading across all three motor connections.
Cheers
Dave R
Yes indeed. I included "internal" break.
Yes indeed, but I'm not convinced how good the measurements were.
Just like mine did before it stopped completely. Time for you to clean and oil it.
I've gone back and retested.
Mains in (blue and brown to 1 and 2) floats around 242V according to my cheapo meter.
I tested 1 (blue in, brown to motor) against 2, 3, 4, 5 with each switch pressed in, and all floated around 242V on each test so effectively all at the same voltage.
So presumably something not working as intended inside the motor.
Noted that with all three switches out 1 + 2 still shows around 242 but 3,
4 and 5 show around 20V. I have no idea if this is significant or just an artefact of my auto ranging meter.Cheers
Dave R
Well, I often take it down and clean the body, grille and fan etc but other than applying oil externally to the bearings, I admit to not cleaning them out as such.
I haven't cleaned them as such because they are the oil-lite(?) type and I didn't want to wash out any of the built-in lubrication?
Cheers, T i m
Oilite doesn't last forever.
The 20V will be pickup via stray capacitance across the wiring, or magnetic pickup by the motor from nearby fields.
It would be interesting to know the wattage of the motor, which would govern the current it takes when powered. You could measure this with an AC current meter across one of the switches, i.e. power the motor via the meter instead of the switch. If the current is zero there is a break in the circuit. If the current is as expected the rotor is still too stiff. If the current is much more than expected there is a short in the windings.
Indeed ... however, I'm not sure how much they will dry our even if not used (as it hasn't much)?
Cheers, T i m
Vegetable oil polymerises over time (that's how traditional varnish works, with a little help).
I've answered my own question. There is a replacement motor available online at about £50. The label on it says 80W 1.5uF. That equates to about 0.3A AC. (The 1.5uF capacitor need to be rated for 240V AC).
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