12V thermostat temp controller for heated pad under water tank

[Glenn]

Can anyone recommend a good 12V thermostat for wiring into my water tank heated pad?

I bought these pads, and they work, but the little thermostats that came with it are junk……pad came on in the warm weather right away (I followed schematic- red wire hot / blue wire ground…….China?

https://www.amazon.com/gp/aw/d/B0B1DLXRY2?psc=1&ref=ppx_pop_mob_b_asin_image

I bi-passed it and wired in one of these;

https://www.amazon.com/gp/aw/d/B08W2BYG2L?psc=1&ref=ppx_pop_mob_b_asin_image

The ambient temperature readout works, temp probe works, and I can set temp but it acts like it set to furnace mode— can’t get relay to close for cooling- lower set temp. I hooked up a LED indicator bulb so it’s easy to see it working - and heat pad get warm when working- but not at the right temp.

I sent an email to China - but there’s no details (?)

I don’t mind spending the money if someone can recommend a good quality, tried and proven product.

Thanks!!! Glenn

Post Edit: thanks to a reader review I found the below manual that shows how to set and change the P0 through P9 codes. Hopefully this works.

https://images-na.ssl-images-amazon.com/images/I/516SWXST1NL.pdf

 

[Glenn]

I found these, they work perfect!
Super easy to set the temperature, but reads out in Celsius only. Two wires in (power), two wires out (load) and the temperature probe…… doesn’t get much easier than that!

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www.amazon.com

I got rid of the cheesy wire splice clips that came on the heating pad, and soldered and added heat shrink. This also eliminated the little (hockey puck) thermostat wired into the pad. Drilled an oblong hole and inserted the temperature probe against the bottom of the tank about 6” away from the heating element in the pad.

When I emailed the Chinese seller and told them the first controller didn’t work even with the probe inserted in a glass of ice they said it won’t work that way…..wait for winter and it will probably work…..”Are you kidding me!!!?? Like the probe knows it’s really summer??

Anyway, I bench tested and this one works perfect while faking out the temperature in ice.

Below: also tested the heating wire for my battery base

Below: With the box I built to hold the water tank, the wood panel is easily removed (held in place by duct tape) for replacing the heating pad and wiring.

 

[Glenn]

I wanted to update so as not to mislead anyone on this product:

The seller / manufacturer states in their product info “10 amp max”
After looking at the wire size (line and load) on the controller and my length of wire run I wasn’t comfortable with wiring it directly to the load.

From other reviews on the web this seems to be a common concern with these type of cheap electronics from China and their selection of wire size.

For comparison this is 16 AWG that is in my hand.

While it is probably overkill I had several “NO” 30A relays laying around. I used the small load wires (yellow and black) from the temp controller for the relay coil (terminals 86 & 85) with 16 AWG coming in to terminal 30 (and a jumper with a diode to the red temp. controller wire and 16 AWG from terminal 87 to the water tank heating pad.

I ran a dedicated 16 AWG ground to the heating pad as well, and jumpered a ground wire to the the small black ground on the controller.

Being the wiring was so small, and to protect the circuitry inside the controller I added a flyback diode to the relay

It was a little extra work but I am happy with the finished heat control for the water tank

The heater pad has a load amperage of 3.28 amps but with the location of the “Heater Switch” located by the tailgate I ended up adding another 15’ to the circuit between the switch leg and added ground to the heating pad.