Magnet Valves

After chasing vacume leaks for a while I recently figured out why my heater controls wern't working. The main source magnet valve is "shot". I've been told just to bypass it and it's no big deal. I was told that the valve is only used to keep the settings accurate right after startup. I'm looking for a new or used valve but does anyone know what this valve is for and what detriment there will be to bypassing it?

thanks,

Steve