[BingoRingo]

The block heater thermostat is in the three prong plug. That is why it is so large. This has nothing to do with the coolant temperature.... just the temperature of the plug. Medicrxdoc has an excellent point in ensuring that the plug is on the outside of the engine compartment to measure the ambient outside air temp. I have checked mine with an ohm meter, and above -18C or 0F the circuit is open, preventing current from flowing to the heating element. The dealer that told you that the block heater will run at any temperature colder than the coolant temperature should not be a dealer!!!!!

Please provide some technical sources for what you're saying, because this seems like a lot of nonsense to me. I live in Québec and I've used a block heater for many years, it works when you plug it in, and if the coolant is colder, as it has been mentionned above. It is suggested to plug it in when the temperature goes below -10C (which is 14F). At temperatures way above 0F you can see the difference when you crank it up, so I assume it's been working!

If yours doesn't work above 0F I suggest you have your unit replaced.

 

[BingoRingo]

I read the Owner Manual and yes, it does say 0F (-17C). It wasn't like this on my previous cars that's for sure, I find it very strange as even where I live it rarely goes below 0F and we've always been told to plug it in below -10C. Maybe the new engines can handle cold oil better?