carrier 58ssb.we replaced control brd,sensor,ignitoin modul,and still doing the same .pilot ignit but main valve dosn't open up.all saftey ok,wire harness ok.i have only 8 volt going 2 main valve.

need roughly 24v to main valve to open. The money you have spent replacing parts could have easily paid for a pro to come fix your problem. Have you checked pressure swithces? Need to find why you are not getting proper voltage at gas valve.

i did by pass it.its weird ,ground is good,checked every thing all seems 2 be ok but iam not getting 24 v 2 main valve.

Take the wires off the main valve and measure the voltages during the pilot and main valve phase.