Defrosting - Part 4

After that fun experiment, I really couldn't get myself back to sanding. So, today, I am going to talk through the electrical set up. I will eventually get back to sanding and Bondo, and more sanding and then primer... and more sanding...

12V and Grounding

routing wiring

Unlike my stereo installs, this time I started with the most basic of wiring: B+ (12V supply) and ground. For the supply-side, there was one remaining basic bladed fuse spot in the battery-top fuse location that wasn't already in use. I spliced a 12ga wire into that spot, and ran that wire along the other back-to-front wires along the passenger side. Leaving myself plenty of extra length, I stripped the end.

Then I switched over to the ground side. Again, with a 12ga wire, on one end I added a ring terminal and screwed it into the rear cross-beam where I have the radiator fans grounded. On the other end, I added a female spade connector. With these 2 wires, I tested the heater to make sure the fan would spin at different speeds based on which of the 3 male connectors was given 12V. First, of course, I added a 20A fuse into the bladed fuse spot. I felt this would work, since the heater unit worked before, but again, I probably could have tested this when the heater was freshly out of the bus and on the ground rather than waiting until it was installed, register constructed and installed, etc.

All 3 speeds work. While the fan was running I crawled out from under the bus and checked the air flow at the windscreen. I don't think the lowest speed will really be terribly useful, but the middle and upper speed should be sufficient to clear the screen, I think. Any of them will be better than the squeegee / towel method bus drivers usually use.

Control Wiring

finished view from underneath

Satisfied that the fan will work, I shifted over to how to control the fan. In my shelve of random stuff, I have about 10 meters of trailer wiring. This is a flat cable which contains 4 16ga wires. I felt that 16ga was too thin to carry the current for the middle and upper speed, but should not overheat for the lowest setting. After my findings above about the usefulness of the lowest setting, I'm not sure it will be used much anyway. So, my thought is that I will send 12V from the supply up to the fan switch through one wire and the signal for which speed will pass through the other 3:

Red - 12V
Black - low
White - mid
Green - hi

Similar to the cable I sent front-to-back for the gauges earlier, I sent this cable along the main harness, through the center belly pan and through a new hole I cut next to the other 2. I made sure this hole was fairly large (1/2-inch) so I could send a thicker control cable through that hole later. With the cable hanging on the emergency brake handle, I wired up the rear end. First, I removed about 4 inches of cable jacket so I could work with the wires individually.

To the Green and White wires in the flat cable, I attached female disconnects. I put together a pair of 12ga wires with female disconnects on either end, each wire is about 40 centimeters (15 inches) long. These will go from the relays to the fan for the mid and hi speeds. I put together a pair of 12V supply wires for the relays: each wire is about 10 centimeters (4 inches) long with a female disconnect on one end and a long (1cm) stripped end. The stripped ends were spliced together. These stripped ends were then fed into one end of a larger crimp-splice. Into the other end went the 12V source from the battery as well as the Red wire from the flat cable. I did something similar for the ground side, creating a pair of short wires that were then spliced into the ground for the heater. With all the wiring ready, it was time to plug in the relays.

Relays

these area a matched pair. Mine aren't

I was fortunate to have 2 12V automotive relays in my cache of electrical stuff. While they were both old Radio Shack relays, they were not identical so the pins had different arrangements of pins between them. Of course, my eyesight isn't that of a young man, so each pin was managed carefully. I started with the ground wires going to pin 85 and the signal wire going to pin 86. The 40cm wires connected to pin 87, with the other end going to their respective fan pin. Last, the 12V wires connected to pin 30.

These relays delivered with a mounting hole molded into the plastic housing, like the picture here. Most folks would send a screw through that hole and mount it into the body somewhere. Well, first, I guess I'm not most people and second, getting a drill up under the bus with a flat enough angle to put a hole through the crossbeam, and high enough to keep the wires up out of the air stream was simply not possible. So, instead, I ran a cable tie through, and zipped them up to one of the steel tubes running just under the floor. This held the relays up near the floor. Last, I wrapped the wiring with one of those plastic wire loom things so rather than seeing a bunch of wires hanging around, you only see one black cable.

I tested the relays before I moved on. I did that by simply jumping the 30 with the corresponding pin 86. Once the relay clicked and the fan spun up, I moved on.

Fan Switch

silver on the knob may be too shiny

With the fans all wired, I needed to put in a switch. I did not want to reuse the old vanagon rear heater switch again. I was unable to get it to mount well before, and there are so many viable alternative options out there. I went with a made-in-USA INDAK switch. These have a standard 1/4 inch shaft, but the threaded mounting shaft is slightly thicker than the standard hole in the bus dash. I had to expand the hole with a drill bit to 11mm. On the side that is buried within the dash, there are 5 pins, though I only need 4 of them. The extra one (labeled "C") is for powering a clutch or lighting a bulb to let you know the fan is on. I think we'll be able to figure out if the fan is on without a light. I wrapped that pin with heat shrink so it wouldn't accidentally short out. Of course, when I run the battery down because I forgot that the fan was on the low setting, I'll post about it. Hahaha. I checked the length of the flat cable and then added female disconnects to the 4 wires. Following the table above, I plugged in the switch.

pay no attention to the dangling wires

I ran one more set of tests to make sure the fans spun at the right speed for the various switch settings. Once satisfied, I slid the switch through the hole I had expanded earlier, threaded on the mounting nut, popped on the knob and called the electrical done. Hazah!

So, I guess that's kind of it for the defroster for now. I will improve the sourcing of the input air as well as add a control for the amount of coolant flowing into the heater core, but I don't know when I'll get to that. Frankly, the way I've been avoiding the Zed bodywork, it could start tomorrow. Hahaha...

Thanks, as always, for following along. Stay safe. Please wear your mask covering both your nose and your mouth (seriously people. that much should be obvious). A mask is not a political statement; it is to protect the people around you, whether you or they believe in CoViD-19 or not.