The problem is that water either falls directly into the control shafts, or more likely that it spills & runs under the stovetop & later condenses out on the controls. The water on the electrical controls creates an electrical "leakage" that can then errantly fire the igniters.

The hairdryer trick can work to dry things out, but only if there is just a tiny bit of water. At times I've helped out the drying by spraying just a tiny bit of WD-40 at the control shafts. However, if a large spill occurred, neither of these solutions will be permanent. The hairdryer can't evaporate large pools of water trapped under the stovetop, & this water will later evaporate some more & then once again condense on the controls.

To more permanently solve the problem of excess moisture under the stovetop, you will need to unscrew & remove all the burners, lift & tip the front of the stove on its rear hinge, & prop it open with a stick. Then you can clean out what is likely a wet gooey mess (that may also be moldy). Uck! The good news is that once everything is clean & dry again, the problem will be solved... at least until the next major spill. I suppose one could apply silicone around each burner tray to help prevent spills on the stovetop from running underneath, but the problem hasn't happened to me often enough to drive to this (& the burner trays are easier to clean if they can be occasionally removed from the stove).

Be sure to unplug the stove (or turn off the circuit breaker) before reaching under the stovetop where there are electrical wires and before putting your hands anywhere near the malfunctioning igniters at the burners. I thought I was being careful as I cleaned out under the controls, but I got bit by the 110V AC anyway. While I was lucky & the shock I got was not bad, your mileage may vary & such a shock could be fatal. Remember, we already know moisture is causing 110 volt current to leak to the igniter voltage step-up circuit; it is likely also leaking elsewhere. The igniters I suspect won't kill you, but they could leave a serious burn. Also, the natural reaction is to jump back & this might cause you hurt yourself in another manner (like perhaps causing the stovetop to drop on you or somebody nearby).

BTW, people have commented that all the igniters fire together when the controls get wet. Actually, all the igniters fire at once even when you manually turn on just one burner. People don't normally realize that all the igniters fire together; what they notice is that one burner ignites as they turn on each control. Only those burners that have gas flowing to them ignite. There is little fire danger from just an errant spark, even if there is no one is around.

Water can also cause igniters not to fire when they should. If instead of the controls getting wet, one of the igniters gets wet by an overflowing pot, the moisture may suck all the available voltage & there might not be enough "juice" left in the igniter circuit to spark some or all of the igniters. Therefore, if you find one or more igniters won't fire, lift off every burner's 2-piece flame spreader assembly & make sure the underside is completely dry. Chances are one or more of these assemblies is wet. Be careful though, any burner in recent use will be hot!

Another word of caution. Proper burner flame functioning relies on the stove being almost airtight between the stovetop & its undersides. Therefore, before placing back down the stovetop, make sure the gasket between the top & the bottom of the stove is intact (and if necessary repaired). I had to glue my gasket back down, as it had gotten wet & the adhesive that holds it in position had failed. Also, when replacing the burner trays, each burner jet must be drawn up by its two screws to prevent the improper introduction of air from under the stovetop to the flame. Use care not to cross-thread these screws or eventually they will strip out & no longer accomplish this task. No electric tools on these screws; carefully start them manually in the previously formed threads & then use a screwdriver to slowly draw the jet to the proper position (without overtightening). If these screws strip, you will need to restore the airtight integrity of the burner assembly by going to an automotive or hardware store & getting "speedi-clips" or by fashioning some other solution. If you don't, the burners won't burn properly, and it could also allow a flame to sneak under the stovetop where it could cause a fire.