The burner has a small explosion proof electric motor on it that when called for burner operations, turns on which spins a small impeller or fan to produce air for combustion. Also attached to that shaft is the fuel pump which pushes the fuel through the nozzle for combustion.
Guessing here not being able to listen to it myself but, either the motor is going bad or the impeller (fan) is out of balance. You have to take it pretty far apart to know which it is but certainly doable.
The motors are pretty expensive, the fan is not. The bearings for the fan are cheap also. If this is a new situation, it is most likely failing bearings in either the motor or impeller.
I doubt it is the fuel pump, it is very small and has such little rotating mass I would be surprised if you could tell it was failing unless it was dripping fuel.
Assembly, fan motor fuel pump and housing with impeller inside:
12 volt motor:
Old style fuel pump (depends on the year).
Impeller itself removed from the housing. It is possible it has failed or has something lodged in it causing an out of balance issue.
Hope this helps.
Originally Posted by Timaz
My Aqua Hot vibrating more then normal. I have checked the motor housing and it is nice and tight. (Can't jiggle it)
Any ideas where to look next?