Caution light comes on,rarely used heater. any thoughts?

MILKHOUSE HEATER "CAUTION LIGHT" SOLUTION: Before I explain, let me clear this myth up: this is NOT an issue with the pendulum safety switch (some mistake that for a "mercury" switch). To begin, unplug the heater. Open it up and clean it out. I mean, buy a can of non-chlorinated brake cleaner and squirt all of the contacts good. Below the fan there is a sensor mounted on the heater element box on the bottom. That goes bad and causes it to trip. While you are there, squirt the motor bushings good with the brake cleaner and dab a drop of synthetic motor oil (just a drop) on EACH of the two motor bushings. Personally, I rewired this and bypassed all of the safety features. You can bypass that sensor without soldering or cutting any wires. All you have to do is unscrew the wires from the holder and then unscrew the tiny nuts and tiny bolts. Then bolt the together at one end (note the position) and put it back in the holder and tighten the screw to hold it in. This method fixes the issue completely as it removes the sensor from the equation. In fact, I just did that on my third milkhouse heater and it has been running solid for the last 15 minutes. Use your modified heater with caution! Let the brake cleaner dry before you energize this device!

Try calling 1-866-876-4332 ext 224 for tech help, it worked for me.  I only needed a temp
setting/off switch to fix mine.