See Page 32 on the same problem with DC04STDUK. Adge's answer is spot on, including the frayed cable being the culprit! and yes, a small tab on the yellow button snapped as I removed it - but a new button has got to be cheap.
Bob Jones
August 2007
I can answer this question...
how do I gain access to the wiring of the on/off switch on a Dyson DC03?