How do I check to see if my block heaters bad
 

Block heaters not working do heater grid relays control this or how do I check to see its bad

It's just like a lamp or any other heater. Start by checking the cord. If it's good replace the heater. You could also check resistance on the heater and see if it's open.

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The easy check that will give you an idea that it is working is to just watch the male plug when you put it into the female receptacle and put it in and out on mine I will see a spark/arc and know it is working. can take a Volt Ohm meter and check for continuity, should not be an open circuit. lastly is to use a clamp on meter to check the amp draw and this is the best most reliable way.

Plug it in, and listen for a crackle like sound after 10 seconds or so. After a few minutes, the block heater should have heat on around where the cord plugs into it.

Something we all failed to mention. Does the truck have coolant in it?

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