Hi to you all
I had a problem with a gas heater and hope to find here someone with expiriance in the field that can give me a tip.

The problem is this:
Gas ducted heater......besic one with no draft inducer etc'
Consist of stand alone pilot,gas valve,simple thermostat(on-off,temp set).
The problem is:
the pilot is lit and when you call for heat the burner lit--no problem.
After a while I shut it and wait a few minutes and call for heat again------sometimes its re lit ok but some times there is a big WOOOF and a big flame an thats it.....probably the big WOOF is shuting the pilot and the unit stops working.
I must say again: old fusion heater, no pc boards just a basic heater.
I must say that I have checked the press' and its ok
Also the fan is working ok and continue to work for a while after temp is met.
I am trying to think about faults but allways come to:"if there was a problem then it will do it in the first time and not in the second or third"
I will appriciate any comment on that.....maybe someone came across problem like this
Thank you all