Fridge Temp Control Question

wnjj wrote:

BFL13 wrote:

wnjj wrote:

BFL13 wrote:
I don't know if the terminals for the 12v element on the board, when seeing the 12v would "back feed" the board, same as if the board were getting power from its regular 12v inputs.

Yes, it would likely back feed into your whole RV 12V system. If you do want to go this route, buy a 12V relay and use the wires heading to the element to power the coil and then use whatever voltage the 12V element can take through the switches terminals to the element.

Still not clear on this. You have the relay being operated by the temp control switching the 12v element terminals? So you still need regular 12v into the board at its 12v input terminals.

Now the 16 or whatever voltage supplied externally to the element is being switched by the relay.

How do you get say 13v to the relay from the board's 12v element supply terminals, while the relay is switching say 16v? Two different voltages. I don't understand how this relay works so it can do that.

Basically, the relay coil “replaces” the heating element as far as the control board is concerned. Instead of switching the element on, it activates the relay coil. Then the control board can continue to operate at 12V. The heating element is connected from a separate supply (e.g. 15V) through the relay common and N.O. pins to the element. Connect the supply to the “common” terminal on the relay and the element to the NO terminal, with the other side of the element grounded. If you figure out which is already ground, you can just leave the element grounded at the control board connection and add the coil ground to it.

I think I got that this time! Have you a link to such a relay with illustrations for the terminals you describe--"common", N.O. pins, etc? Thanks!

I have ordered a 120v element but it is 325w instead of 300w in hopes I can make it work from the 120v output from the board. The specs for the 300 and 325 in amps and ohms are not much different.