[SteS]

Dave,

I suspect, with it being a 4 wire DC brushless with a driver board that two wires are power and two wires are for some sort of PWM signal to control the speed. Sometimes with no signal on those, the fan will run at full speed, but without knowing before you start it’s pointless going that route.

Would you have any other recommendations on how to move forward with diagnosing? It’s clearly something to do with the fan but I really don’t want to drop £100 on one and find it’s still doing the same when I swap it, because it’s in fact the main board that’s gone.

Thanks.
Steve.

[SteS]

Dave,

I haven’t explicitly tried running without the element, but I will add one thing I didn’t mention in my original response, for fear of muddying the waters. The element was my first suspect, and without having had the thing apart at all, considering the element was £30 and it’s the thing that often goes in electric ovens, I ordered one first, and the one that’s in it now is actually the new element – and it didn’t change the behaviour at all.

Granted that doesn’t demonstrate if the board is happy with no element but a fan connected. It could be something to try for sure.

I tried several settings, and I think yeah, anything that powered the rear fan up killed it. The top fan, however, ran just fine.

I’d like to try the fan directly but I’m just not sure what sort of connection it requires. It has four pins, red black yellow and blue, and it’s tempting to assume that red and black are power, as there’s a prominent marking on the back of the fan’s driver board that says “24V DC 4.8W”, and that the yellow and blue wires are possibly a OPR pulse telling the rest of the system that the fan is rotating, but that is, I will stress, a complete guess. The motor seems to be fairly clearly of the DC brushless variety, so it has a lot of complexity on the driver board. I’m assuming as I say the 24V just goes in on the red and black, but I don’t know if it needs to see a resistance or a short or whatever else on the other two wires in order to fire up, or if it’s just a report back on the RPM, or some other status. Or, indeed, whether it’ll just fire up with those two pins left disconnected.

In other words, at the moment I don’t know enough about that motor to know if, if it were to stay stubbornly stationary on applying power, that’s because the motor is dead, or because I’m just not giving it the right signals to get it to kick in.

Thanks
Steve

[SteS]

Dave,

Thanks for the response.

Honestly, I doubt it’s the power to the oven. This oven is paired with another similar single oven with microwave functionality, and behind them, both of their power cables are wired into a junction box, which then goes to the cooker isolator up on the wall. The other oven has no problem at all, and the wiring is all solid – I had to disconnect the oven that’s having problems from the junction box directly, as the cable isn’t long enough to pull it out the cabinet otherwise. I double checked all the wiring before I started that, and it was all in tight and secure.

Particularly considering I can get the elements to fire up, in the grill and the main oven compartment, they’re a few kilowatts a pop, whereas the fan can’t be more than about 10 watts, I wouldn’t have thought.

Nothing’s jumping out to say the supply has anything wrong with it, honestly.

Thanks again.

Steve

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