[camr]

The block heater will not begin heating until the outside temp is below 0F or -18C. It is alot colder than that where we live. I am a real believer in using the block heater for about a 3 hour period to reduce engine wear. I wish that the block heater would function when the temp is below 10C.

 

[camr]

Applying a bag of ice to the plug end will not be cold enough to close the circuit switch in the thermostat plug end. The ice will only get down to 32 F, and the switch closes at 0 F. With regards to replacing the thermostat plug with a regular plug, there have been posts that have explained that allowing the block heater to run at outside temps above 0 F will cause the system to throw error codes. GM designed the system for a reason, and the reason probably was not to save power. I'm thinking that the block heater element is possibly placed in a close proximity to an engine computer temperature sending unit. Maybe one of our tech members can explain.

 

[camr]

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!!!!!