I changed the water pump and drive belt this week, and might have killed my block heater. I drained the radiator / motor of coolant completely, then realized after 15 minutes or so that I still had the heater plugged in. [dummy]So I unplugged it and didn't think much of it. I did the pump and belt later that night and took the truck for a test drive, and all checked out ok. I plugged the truck in when I was done for the night and popped the fuse. I've put in a new heater cord, tried different house circuits, and switched extension cords. It pops the GFI breaker instantly when I plug it in. Did having it plugged in with no coolant short the heater somehow? I don't understand it though, because it wasn't popping the circuit when it was plugged while empty. Is there something else that could be causing this?

Sounds like you burnt it out. (Over heated) You opened the circuit and it wont short out when the block is empty but when you add coolant it shorts and pops the breaker.
Topper

Take an ohm meter reading between the two prongs, and between each prong and the ground.

I want to say it should be around 7 ohms...

So what's the replacement process on these? Are they threaded into the block, or is it a clamp on freeze plug style? I just spend a load of cash on coolant last week, and don't want to loose more than I have to. I want to pull the old one and slam the new on in as quickly as possible so I don't have to replace more fluid than is necessary.

Where do I get a replacement that isn't $90?

It list on Cummins website for about $30. I assume the $90 you have is from dodge. Looks like you need to find a Cummins dealer near you.

I cannot find any parts on their website? What am I doing wrong?

never mind

I guess you found the QuickServe part of the site? It lets you buy parts from there. I never have so I don't how easy it is.

I found the part. The site is cool, in that it gives you diagrams and schematics on parts you are looking for. The problem I have, is that I can't see prices or a way to actually order a part????

Here's a picture of the block heater that the sight says matches my engine (based on serial number)

https://quickserve.cummins.com/rtgraphics/english/parts/ch/9/ch900zu.png