Chasing the Hapy Electrical Gremlins (final)

Well, it may have taken a while, but with today's post, we are done with the re-wire of the "fuse box harness". I did not mean for this to become such a large endeavor, but that's what happens when you lose focus for a few minutes and cut some wires too close to the fuse-box for you to re-integrate them. I was asleep at the switch and missed my usual release time, so it's a few hours later than usual this week. Hapy last day of the worst US presidency in modern history; may the transition to the new guy be a smooth reflection of 200+ years of our democracy in action.

I realize that for many readers, this series has not been terribly interesting. I get that. Electrical sucks. However, if you were thinking about doing a swap, I think this series helps demonstrate how much of the swap work is done with a multi-meter, and how little is done with a shop-crane / engine hoist (or a floor jack).

Today, I will go over my steps to determine what went wrong in my system test in part 5. Apologies for no pictures of my testing. I'm not sure what would have been picture-worthy, except, maybe, my "fused wire", but that's not terribly interesting, I don't think. I mean, it's just 2 wires, each with a male wire connector on one end (to plug into relay sockets) and a female connector on the other. The two wires are then joined with a bladed fuse plugged into the female connectors on the 2 wires. So: male connector - wire - female connector - bladed fuse - female connector - wire - male connector. Easy peasy.

The T-12

Before I get into it, I realized after posting part 6 that I put a picture from when I was integrating the T12 wires into the front-to-back cable, but I didn't give any context nor explanation. That picture was illustrating that once I cut the cable, it wanted to spring back through the engine compartment and over the driver-side axle. Resisting that spring-effect does not help one make solid wire connections. So, I held the cable in-place with a vice-grip. Some of the ShadeTree solutions are just funny enough to be photographed.

Isolate

I mentioned in part 6 that I removed the diode between the RUN and START relays. This isolated those 2 circuits. I continued down this path by pulling all of the relays and fuses from the new fuse box, disconnecting the two always hot (30) circuits from the battery-top fuse box, unplugging the "D plug" from the alternator and removing the connection to the reverse switch. So, now, the engine and new fuse box are completely isolated. My plan to find the issue is from here, we slowly add things back in, testing each planned connection first.

Original Bus Loom

I started with the main bus. This wasn't touched, but still, if we can eliminate that huge variable, so much the better. So, I turned the key to run, flipped on the running lights and then the headlights. I even flashed the high-beams. Everything was working great at this point, but nothing in the old loom was changed. I did discover that one of the grounds on the front (front-is-front) of the dash was falling off, so I tightened the connector with some needle-nose pliers and kept moving. I felt confident that the test I had just done was not going to trigger a battery discharge. I did not have that feeling for anything I spent weeks modifying, so the rest of the tests below were much more careful. The next step is re-integrating the donor stuff.

New Fuse / Relay Box

My process was pretty much the same for evaluating and connecting the donor stuff and new fuse box: Identify the circuit, and before you connect it, check the amp draw. Pretty much, regardless of the reading, I then tested the connection by bridging the gap with a fused wire. I would select a fuse that was appropriate for the circuit being tested. In the case of the red always-hot wire going to the new fuse box (relays 109, RUN and START), I used a 20A fuse, and it didn't pop. To be fair, this test really only proved that this red wire was not itself going to ground independently of the key going to "run"... which wasn't happening. And, the relays were all pulled when I did this. So, this test was not as meaningful as I thought it was when I did it. I connected the circuit and verified voltage at the relay 109 socket 30,  before moving on.

Once I had the main power to the 109 relay, I popped it in place and the tested the RUN relay socket. Similar to the process I described above, I checked the amp draw between pin sockets 30 and 87. Then, I made the connection between them with a (20A) fused wire. Once validated, I only put the relay in once to confirm that turning the ignition key caused the same behavior. It did. After that, I did not plug in the relay simply because the ignition key is 15 feet away from this fuse box, and I just did not want to have to keep going out from under the carport into the pouring rain. Besides, this kept the testing isolated, as I continued to trigger RUN tests with a fused wire jumping from 30 to 87 in the RUN socket for the rest of the fuse box tests. I validated that socket 30 of the START relay socket was present. Yep yep.

I repeated this testing process with each of fuses 1-3 (11/15, 12 and 29 respectively) in the new fuse box, and then the connection with relay 109 before inserting relay 109. In each case, the steps were to check the amp draw first, then insert the fuse. Next, I repeated that process with fuses 4-6 (32, 34 and 43 respectively). I had a moment where my relay 109 was humming during the investigation of fuses 4 or 6 (34 / 43) which I tracked down to my not having had two grounds (one for the ECU and one for the main harness) re-attached during testing. Now, after the fact, I think this could have been a big deal, but as I worked through these steps, it was not apparent.

At this point, I had all 6 of the fuses installed and the 109 relay. When I bridged across pin sockets 30 and 87 of the RUN relay, the dash-pod would illuminate, the odometer displayed and idiot lights would come on. After a few seconds, most of the idiot lights turned off. The glow-plug light flashed though, and I realized that I had not yet tested the glow plug relay. I repeated the process for the glow-plug relay (180) and last, plugged the relay in. Once power was applied via the RUN socket, everything was the same except the glow-plug light winked out with the others. I had not yet wired in the always-hot (30) for the glow plug, though, so that was next. Same amp draw and voltage check process, same result.

Front-to-Back Run Relay

I figured testing the RUN and START relays was next. First, I plugged in the alternator "D" plug and tested everything again. As before, everything was as it should be. As I worked through this stuff, I suspected it was one of 2 things: either it was related to the "other 2 relays" I haven't really documented -or- it was because of this plug, since I split this signal to the front of the bus. So, my next test (of the RUN) relay from the ignition switch would be done first without the "D plug" clicked in.

 

This test was rather simple: stuff a standard Bosch-style relay ( I re-used one of the "53's" from the donor) and turn the key to run up front. I had already done this once before so this should not have been dramatic, and it wasn't. The donor electronics did the same thing as before. Feeling confident, I figured that the starter circuit would be just as seamless. That was not the case, and it was here that we found our cause.

On a side note, the relays with a "53" stamped on them appear in a few places in the TDI relay panel, but they also appear in the little relay box for triggering the coolant glow plugs. So, I figure these should be up to the task of carrying some decent current. Not that either of these do that, but the RUN relay needs to be on so long as the key is on, so I would think that takes some stamina. Oddly, in the 10 years since I first did this, the old Radio Shack basic 12V automotive relay never failed me.

Starter Relay and Starter

I started this test like the others: test amp draw, bridge the 30 and 87 relay sockets with a fused wire and see what happens. The starter grunted like it was gonna try to start the engine, so I quickly pulled the wire and figured things were fine. I put another spare donor "53" relay in the socket and turned the key to RUN and then to START. This time, what happened was what happened during my full system test: a pop followed by everything going dark. Concerned that the starter was blown, and that was causing the problem, I pulled and tested the starter.

I have an old battery sitting on my garage floor for things like this. I ran a set of jumper cables from the battery (negative to starter mount tab, positive to positive post on the solenoid. Then, with my fused wire, I jumped from that positive post to the start trigger and the start fired right up. 

Since the starter tested fine, I slapped it back in. While I was on my back working the long mounting bolts back in, I remembered that I had split the START signal at the ignition just like I had split the RUN signal. At the time, I had not yet hosed the wiring in the donor fuse-box with my aggressive wire-cutting, so I was intending to keep the original starter trigger from the ignition, but to also send a start signal to the donor ignition switch wiring so the ECU knew when a start was being attempted. This all made sense at the time, though now in retrospect I realize that the ECU doesn't need to know you're starting. Later, after this effort mushroomed, I connected the starter signal to the T6 like the donor engine was triggered, and forgot about the old start signal wire. So, now that none of that old stuff is being retained, that old start signal was going somewhere... and possibly shorting us out. 

Start Trigger

I very much wanted to test this theory. First, I confirmed that I had not screwed up anything new: get the battery hooked back up, verify it's at 12V or higher and reset for the prior test with the RUN relay, etc. Turned the key, and we're looking at a code-free dash-pod again. Nice. I turned off the key, and cut the wire from the start side of the ignition key to the original bus starter wire, and reset the key to RUN. Back at the fuse-box, I tested the START relay and the engine tried to start. Hoping that we may have found our root cause, I went back up front and turned off the key.

Remember how I removed that diode between the RUN and START signals? I confirmed that the RUN side of the ignition switch continues to deliver 12V when the key moves to START at this point. I simply measured the voltage at RUN when I turned the key to START. Since the START position was now only sending 12V down to the relay socket, nothing happened. We did still have 12V at RUN, so the diode is not part of the new wiring.

Back at the bus rear, I replaced the donor "53" relay into the START relay slot, plugged the alternator "D" back in and returned to the front of the bus. I turned the key to RUN... all the usual lights lit up. I turned the key to START... and Hapy started. He sat idling while I danced around a little bit. I did notice, however, that the battery light on the donor dash-pod was still on. So was the light on the bus dash. So, while Hapy starts and idles, some issues remain. Okay, we'll figure that out... Also, after a few minutes, Hapy's idle increased from bouncing around 900 to... 1200 rpm firm.

Next!

Ugh, the dreaded 1200 limp mode is still around. I'll be working on that next, as well as hooking up the reverse lights, and looking into those other 2 accessory relays that apparently were not part of the problem. I have some documentation to mop up with regards to the diagram, so I'll be spending a few evenings getting that done too.

I will have different blog posts and titles for all of that stuff (may not post on the diagramming), since this was really about simplifying the wiring. You could argue that this "Electrical Gremlins" series started because I couldn't get Hapy to start with any consistency, and now I can. So, that's it for today. Thanks, as always, for following along-