ignition problem

Steve Gates_3

I have two Larrs pw715 hot water gens controled with a tekmar. Both have been firing just fine for the last three years, until now.

They don't always fireup on first try then l/o. Generaly when having been off for a while. When reset they try once and flame for appr.one sec. reset and they ingnite no problem. We use the off switch for reset not the hi limit reset.

We cleaned the units per tec support, no dif. I tried adjusting the air vent on the gas valve to no avail.

Now what?

Thanks Steve