Fixing Hapy Furnace (part 1)

Having finally arrived at a place where we have some heat while we're moving, I felt motivated to fix the heat for when we are standing still. Today's post covers most of the saga of getting a Chinese diesel heater operational again. Spoiler alert: the heater isn't running by the end of this post.

Brief History

Back in the early days of CoViD, I installed one of those Chinese diesel parking heaters into Hapy (See Parking Heater 1, 2, 3, 4, 5 and Final for deep detail). While I was able to run it a few times, I found that the heater pulled the voltage way down on whichever battery was connected to it. I tried to solve by providing multiple batteries to source from: one to start, one to run, but switching from battery to battery seemed like a bad practice. I had other priorities, so I just let the furnace sit unused. When I did the sound deadening effort and the luxury electrical re-wire, I dismantled the cabinet which housed the furnace so I could get sound deadener underneath it and electrical cables through it. This meant dismantling part of the furnace too. Later, when the band wanted to use Hapy for the album cover, I removed the furnace exhaust so it would not appear in pictures. So, I had a furnace without an exhaust, and would draw way too much juice.

Electrical

Over time, and with more learning about electrical stuff, I have concluded that the wire used to convey electricity but perhaps more importantly the wire for a ground were far too thin. It was due to these thin wires that the voltage would drop so badly as the furnace attempted to compensate. Wires which would have been barely up to the job had the battery been sitting right on top of the heater will definitely NOT be up to the task once you move the battery a few feet away. This is exacerbated by running the ground to the body of the bus instead of back to the battery. The ground location should not matter as much, but I'm citing it as a participant cause anyway. So, addressing the electrical came first after removing the furnace from the bus.

A small harness of wires leaves the furnace body and enters a black plug (see picture on the right). The harness that ships with the furnace includes a pigtail that clicks into the furnace black plug. To my eye, the red and black wires in the pigtail are not nearly as thick as the wires leaving the furnace. This probably saved the manufacturer a few pennies, but the amp draw issue starts right there (and in my case got worse). So, I cut the main power and main ground wires from the furnace black plug and put male/female wire ends on them (12V/ground respectively). I made them different so I couldn't accidentally plug it in backwards. I then prepped a thick 2-wire black/red cable with matching wire ends, and routed it over to the luxury battery. At the battery end, I added a ring terminal for the ground and added a 20Amp fuse into the positive side before adding a ring terminal on that end. I left things detached as I switched to preparing for the exhaust.

Exhaust

From under the bus, it was clear that I had not made the hole(s) large enough for the exhaust, intake and fuel to be easily maintained. Quite the contrary, I had installed it such that once it was all together, it would have to all come apart to fix anything. Frowny-face. So, I started by cutting a 4-inch square hole into the lower belly pan. Many buses do not have these, but I got lucky. Anyway, with the hole cut I could see where the furnace sat, and noticed that the exhaust was getting pinched by the too-small hole in the floor as the exhaust left the furnace. So, I went topside and expanded the upper hole both in the floor of the cabinet and the steel floor of the bus. With the larger hole, the exhaust easily fits and things could be maintained from below. Still, I did what I could on the furnace itself before lowering it in: Connect a 6" long stretch of fuel line, attach a small circle of window screen to the intake (so bugs and pebbles don't get in) and then attach maybe a foot of heat-wrapped exhaust. I set the furnace in place and attached a small subset of the muffler arrangement I had used before: just one rectangular muffler. I may bring the expanded muffler set up for use when we are in tighter camping spots (like festivals), so we can bolt-on some extra quiet. I mounted the muffler to the underside of the frame rail, with the outlet pointing rearward and slightly away from center (picture on the right).

A keen eye can see some fresh Rustoleum primer + paint above the muffler where I discovered some rust had eaten all the way through the body. When I was working on the other stuff I ground the metal down, removing the rust, but exposing the holes. Sadness. That rust traces back to when this bus had a small vent window directly above this spot. That vent window was badly leaking and the rust had already been forming to the point of marring the paint when I bought this bus over 20 years ago. I eliminated the vent window in 2015 (See Calling "glass") with a window I purchased from BusBoys in Redding, CA in 2009. Some things move slower than others.

Fuel

I shifted over to fueling at this point. The fuel line that had been between the included "hard" line and the furnace had breeched, probably when I did the sound deadening. The fuel in the line looked dark, so I dropped the line into an empty pail, and figured I would prime the fuel system, and purge the bad fuel at the same time. Unfortunately, the fuel pump is no longer functional, so I am waiting on a replacement to finish this job.

Afterburner

Back when I first did this job, I bought an Afterburner from the guy who hand builds them in Australia. Apparently, there are people building knock-offs, eating into his business, since they basically have cloned his work. So, if you are looking at getting the much nicer controller for your parking heater, please connect with Mr. Jones in Australia and get the real deal. Anyway, with the Afterburner, I tried to prime the fuel system, but the fuel pump wouldn't respond. When I unplugged the pump, I got a code; I concluded the wiring to the pump was good but pump was bad. So I ordered a new, supposedly quieter, one. We'll see. While I was clowning around with the Afterburner, I got it onto my home network, downloaded the newest firmware and wandered around the new-to-me website that the Afterburner hosts. It's really cool. I am looking forward to triggering the furnace to warm the bus from inside. For reference, here is a link to the user manual.

This is as far as I've gotten. I am waiting for a new fuel pump to arrive. I need to purge the old lines of nasty fuel, and install that new pump. I expect there will be other discoveries, and I need to rebuild the cabinet innards. There's always opportunities to improve things. Anyway, thanks, as always, for following along-