Did you replace the burner with a 118V burner? The Speed Heat burner itself is different from other Frigidaire 6" burners as it's a 118V burner instead of 236. The switch itself isn't the same as the regular burner switches.
If your range uses the original switch, it's a dual voltage switch that flashes the 118V burner on 236 volts for a few seconds after you turn it on. Then it cycles it on and off on 118 volts so it maintains it's temperature to the chosen setting.
The Speed Heat switch, because of the low resistance of the 118 volts burner is subject to a lot of wear from arcing the contacts when it operates on 236 volts. If the contact points go bad, they could either stick together and stay closed or burn and not make contact anymore. Many things can happen, it could flash the burner on for the quick warm up then nothing, it could cycle on 236 volts which makes the burner red hot everytime it cycles on=off or the "surface" light could stay on when the control is set at off.. In any of these cases, the switch needs to be replaced.
If the burner was replaced with a regular 236V burner, it will stay too cool. If the switch was replaced, there's a special type that is made to cycle correctly with the 118 volt burner (won't do the quick warm up like the original) or you could use a regular 236 volts burner and a regular 236 volts switch like the one used for the rear 6" burner. In both cases, there's one wire from the original switch that has to be removed. The neutral wire won't be used with the 236V switch and burner setup and one of the hot wires won't be used with the 118V switch.
