Heater and Air Conditioner Fix

A/C and Heater Control Panel
A/C and Heater Control Panel

This is my long-term memory for another household chore. Most of my other household fixes are held in memory for me on my YouTube.com channel.

Our studio has a large A/C and Heater unit that was no longer heating. The A/C seemed to be working fine and the fan worked when on heat but the heating element would not heat up. I had opened it up and pulled out the control box a few days ago but only today got back to figuring out the problem. Of course the neighbor came over to help out and offer his expertise.

Everything seemed fine but we discovered that the heating element was not getting any power. Backing up from the element we checked for current across the temperature control — none. We then bypassed the temperature control and the element started warming up.

Behind the cover of the Ranco C21 Thermostat
Behind the cover of the Ranco C21 Temperature Control

Next step was to remove the temperature control and investigate. My neighbor had left and so I tried to figure it out on my own. Not knowing for sure what the problem was, I started looking into the temperature control itself leaving the thermostat out of the picture for now.

Adjusting screw for Ranco C21 Thermostat
Adjusting screw for Ranco C21 Thermostat

In the temperature control I noticed the connection was completed when a lever was raised as the thermostat did its thing and completed the circuit on the connection side of the temperature control. I turned the temperature control dial to watch how this lever was adjusted as I turned the dial to “warm.” Seeing which way it moved, I turned the thermostat adjustment screw to move the lever in the direction I’d seen the temperature control dial move it. After making incremental changes I reconnected the thermostat and tested. Now the heating element had power and our frigid studio had heat again.

Ranco C21 Thermostat
Ranco C21 Temperate Control

Of course I don’t think I’ve taken care of everything. I expect that now I won’t get any A/C due to the adjustment I made. I haven’t checked this yet since the studio needed some heat for a while. At worst I figure I’ll have to adjust it again when we get warm weather. I can get a replacement for this Ranco C21 which, it seems, is officially called a C21 Single Stage Control.

If you have any advise for me or I need to correct any of my description, please leave a comment.