I've got a DC19 back in that 'wouldn't start'. I changed the motor on this exactly a year ago. Stripped it down, tested it with a spare cable and it is indeed dead. So not the cable or switch, continuity test OK on those. Since the pre-motor filter and cyclone were fairly clogged, I thought that maybe it had overheated and the thermal cut out had failed? Swapped it with one from a DC04/7, as they appear to be identical. Still dead.
Removed the brushes to check them and they're fine, being only a year old; there's a little carbon on the post-motor filter, but nothing too bad. The motor turns freely. Resistance across the terminals is 1. There's nothing visibly wrong with the motor at all-all the blown ones I've seen have visible damage.
I'm going to have to replace it again, but before I order the new one, can anyone tell me what might be wrong with it if it isn't the TCO or brushes? Baffled.
This may not be relevant, but the cyclone was full of pine needles (about half a small Christmas tree I reckon)- but there's no way these can have gone on through the pre-motor filter into the motor surely?