Electric heater adjustment

[Ernest Ekberg]

At one of our Lone Star Bird rallies, someone had their bath baseboard
heater out and they were adjusting the cycle time. does anyone remember
how that is accomplished. My heater will come on for 20 seconds and
then turn off. Kinda cool in there these days. I have supplemented the
heater with a ceramic heater, but would like to get the original
working longer. Thanks, Ernie-83pt 40 in louisiana