will not light

[papher51]

I have an older power vent water heater. Fan comes on, pilot is lite, burner will not come on. I checked vent pipe and pressure hose, installed new pressure switch. If I jump the pressure switch wires the burner will light. Any ideas?

 

[LiQuId]

defective pressure switch or perhaps you have a different venting issue as it should work if you are getting proper dravting and pressure in the vent.

pics always help/