Well as I said not my #1
using a volt meter or test light probe the wires to the control board (The ones that come from inside) you can download the manual to find which wire is which
If you have 12 volts on one or the other (Gas or Electric) lines check the matching device line
Also check the two T-Stats with cold tank both should show near zero resistance if you disconnect one (or both) wire and measure tab to tab.
Do them one at a time.. it does not matter which wire goes to which tab so long as the wires go to the correct T-Stat
