Block heater power calculation

[Number_35]

I'm filing some scanned documents, and in the automotive section of my files found a write-up I'd done for a friend and coworker a few years ago, after replacing the open plug for him. He was worried that the heater itself might be bad, so this was to reassure him. (He was from a much warmer part of the world.)

Who else but BITOGers might be interested ...

Edit: He was an electrical engineer, so didn't consider me overly weird for producing such a thing.

 

[B1974]

I check the resistance of ours before winter to make sure they're still working. Those plug ends don't last forever.

 

[Number_35]

I check the resistance of ours before winter to make sure they're still working. Those plug ends don't last forever.

I do the same. The salt spray eats the plug ends up, and the blight moves up the strands. In recent years, I've been saving cords with sealed ends off discarded appliances, and splicing the cords together under the hood. They last a lot longer than the yellow replacement ends.

A few years ago at work I went to unplug the block heater and the end was really hot. I took the truck right over to fleet services, which saw a lot of bad ones. That was the sealed factory end on a 2013 Silverado 2500, and the end was only three or four years old. Sealed is no guaranty!

 

[DemoFly]

I actually don't know the duty cycle of a block heater. Due to all the heat dissipation do they typically run at rated watts the entire time?

 

[B1974]

Block heaters don't shut themselves off, it's just a simple heating element. Some GM ones have a ambient temperature shut off that interrupts the circuit at anything warmer then -18C. But other then that they don't shut off. I don't plug it in until the temp hits -16C, and once below -26C or so I plug in my oil pan heater pad that's 125 Watts to get the oil flowing better. Block heater I'll plug in all night the oil pan heater for 2 hours or less.

 

[B1974]

I've been saving cords with sealed ends off discarded appliances, and splicing the cords together under the hood.

I use the black rubber sealed ones you can buy at CT, but even those don't last more then a few years.

We had a Ford Windstar burn down in out parking lot at work about 20 years ago. The guy wired his block heater to his interior warmer under the hood and it shorted out. I'm not a fan of splicing stuff under the hood due to this.