Another one of “those” subjects. I use my block heater. A lot. Low 50’s it comes on. The preheat time is a lot less and thinner oil can’t be bad. So I went to turn it on, and thanks to my handy dandy AC ammeters I was able to tell there was nothing happening. This is what the block heater looks like out of the box:

Different coaches different setups, but mine is an outlet next to the inverter:

So I plugged a tester into the outlet and it was good. Ergo, heater bad. As you follow the wire up down, through the forest and over the river you will find it next to the oil filter:

Easiest way to get to it is to take the oil filter off. Then I removed the cable and tested it with a multi meter… power. (120V, remember? careful.)

So, this is a simple resistance element that sits in the coolant and heats it up. So when you take it out…. yep, coolant comes out. So I used a nice and clean tub, closed the heater loop, and using a 1-1/8″ socket opened it just enough to get it to dribble. Yes, you can drain the entire system but I wanted to lose as little as possible. A slow dribble takes a while. You don’t want it all over the place getting into electrical connectors. How long? Go inside and have some coffee. Mow the lawn. BTW, when it dribbles you are a half a turn from the whole element coming out and then it ends up in your arm pits as you try to get it back in……….

So how much? This much, about 5-1/2 gallons.

After that it was a matter of some pipe sealant on the new heater, reconnecting the wire and putting the oil filter back on. Now to fill.

Of course while I had all this coolant out it was a perfect opportunity to test it. And it turns out the SCA was a little low, so I added some.

Now there’s a pretty specific procedure to fill the system. Big sticker in the back:

This is a PITA btw because of where the filler on the expansion tanks is located. I used a small hand pump. Takes a while but it’s a lot less messy.

Also poured the coolant through a strainer into a pitcher.

So, I was able to put all the coolant back in through the expansion tank. Then I fired it up. Pulled the digital engine temp up on the LBCU and right at about 200 the thermostat opened as evidenced by the top radiator hose heating up. (I removed the hatch in the aft bathroom to get to that more easily). Then I went under and opened the two heater hose valves. Since I closed them when they were full, I didn’t think there was a need to bleed them as the procedure indicates, but just to make sure I opened the petcock and indeed coolant flowed and the heater worked just fine.

So, now the test….. Waited for the thing to cool down, plugged it in and viola……there is life! BTW it draws 5A, roughly 600W.