Well, we've shutdown for the night after a full day of troubleshooting. Luckily we're at a stop in Jamestown, ND with hotels and food right here, so we're in good shape and good spirits. Thanks for all the posts, texts and calls today - very helpful and greatly appreciated! Lots of locals have stopped and offered to help, but no one has ever seen anything like this. Each time we stop to explain what the sysmptoms are, what the different components are, what we've tried, etc., it just reinforces our understanding of how this truck works (I think that's just the natural process of how we all learn about MVs).
Today we focused on the Power Distribution Panel (PDP) - the mess of relays and circuit breakers on the right side of the dash. We were thinking that was the common point between the dash controls (master power switch and start button), and their corresponding swiches just behind the alternator (apparently a feature of the A1's that allows remote starting of the engine when the cab is raised) - looks like both go through the PDP to control relays that then control the starter solenoid relay among other things. Swapped out all the relays, and replaced three with new ones - no effect. Dash will not light up at all, still have 12v power to all lights. Verified that the starter has a good ground, also.
I've included some photos below of the A1 PDP since there's not much info out there on these. One oddity we can't explain is in the last photo - the relay/breaker box on the far right -the power connector coming in from the bottom right (circled in red) is reading +4v, other relay boxes were getting 12v inputs.
Based on many suggestions that came in through this thread today, we've worked up a pretty good sequence of testing for tomorrow:
- Verify battery grounds
- Verify master relay operation (in box to the right of battery box; there is a rotary switch on the bottom of this one). Will test both from dash and from remote switches by alternator.
- Remove control cable from the Load Battery Control Device (LBCD - reverse polarity ddevice) and attempt to start (if success, get in and go!)
- Safe the LBCD (disconnect batteries, discharge capacitors via ignition switch)
- Verify all battery voltages
- Bypass LBCD by stacking the leads on common posts for each side (12v -> 12v, 24v -> 24v)
- Reconnect batteries, attempt to start #2
If that doesn't work, we're looking at ideas of what else to bypass to get power to the dash and power to the starter. If you have any ideas on the next areas of focus, please post here (I'm also up on cell/text at 619-886-2531).
