Mystery electrical system problem - not sure how to proceed.

[Sunbeam]

[AstoriaDave]

Sunbeam,

I suspect your puzzle has a lot of us very intrigued. Not having a similar boat at hand, I could not follow your description, despite the clarity and completeness. A phenomenal job.

I am very curious what the culprit is. Once I see a schematic, my brain will be a'buzzin'!

[AK Angler]

I've been busy and haven't had time to work my way through the narrative and build a schematic yet... Should be able to get to it tonight.

[Sunbeam]

Thanks for the update, and for taking the time to think about the mystery. On my end the VHF/GPS are still on (and the ACR still disconnected, for what that's worth). Boat's on trailer now as we get things squared away on the outside post-trip.

I think maybe I'll reconnect the ACR and see what happens. Of course the results will not be conclusive either way on that (like they would have been if things went dark with it disconnected), but...

The fine-toothed comb inspection of the electrical will come later today or tomorrow. I sure would like to find something obvious, such as big honking patch of bare wire with a screw through it (never thought I would say that!).

Sunbeam

[Sunbeam]

Minor update:

1) As of mid-day, the VHF and GPS were still on.

2) We re-connected the ACR for now.

3) We laid hands on every inch of that helm feed wire, and looked over everything behind the helm (again) (including removing P-clamps and wire ties to get a better look at it all). Nothing suspicious was noted.

4) We completely "re-filled" the main fuse block where we had been robbing it for spares (which we now have more of).

5) We looked at the short jumper wire between the positive bus and the main switch. Nothing noted.

6) We removed the battery switch from the "wall," and looked over everything. Nothing noted except that I had previously noted the jumper was slightly loose on the switch terminal. First I wiggled it like mad and saw that the GPS/VHF did not even flicker; then I tightened it properly, and then put the switch back.

7) We inspected the #6 cables leading from the switch to the ACR - nothing noted.

8 ) We put a 20-amp fuse back in the "main fuse" spot that we rigged (I'll need to order some of the 30-amp in that other style).

9) For now, as a diagnostic tool, we decided to add an inline, 20-amp fuse to that main helm feed wire, right back by the positive bus. My thinking on that was that if that fuse blows, it tells us it's something forward of that; if the problem happens without that fuse blowing, then maybe it's something else (something inside the ACR? Or?). Ultimately, I'll replace that wire with some new, proper, larger gauge wire and re-do the fuse block, etc.; but for the loads I'm running now it's fine anyway. We'll do that this afternoon yet.

9) Then we'll take the boat out for awhile and see if we can make the problem happen again (plus run the tanks out of ethanol fuel and then put in some "pure gas" I was able to get on shore in a 5-gallon can, fog the engines, and run them dry).

That's it for this update in the Mystery files.

Sunbeam

[ghone]

Great info Sunbeam. Hope you've solved it. George

[Sunbeam]

[AstoriaDave]

If you have a fuse within 7 inches of the battery terminal on that new main line, adequate to protect the wire, you are done. It is there to handle any inadvertent overloads, either from a short, or from the combined loads of the items served by that wire. IIRC, you anticipate running a 6 ga wire as the new main line, with the existing 10 ga wire reserved for expansion, and/or as a voltage source that will be within 3% of the source voltage ... obviously only small draws.

Do not recall where your main fuse is, and what it serves. You need a fuse or breaker on each separate wire of a size to protect it, if that wire runs directly off the positive side of the battery.

[Ray]

That sounds like a good strategy, Sunbeam!

These kinds of things take an inordinate amount of time to solve. It's painful.

[Sunbeam]

Thanks, Ray.

Aaaand, I think after today we have something! I'm so jazzed.

The short version: We seem to have an ACR problem.

The "whole story" version:
So just to review the last little bit, we hauled the boat with this mystery issue. We planned to spend some time stationary on land getting the boat, etc. squared away, so to continue the experiment we left the VHF and GPS on over the last couple of days (parked on the trailer). We had reconnected the ACR (which we were slightly suspicious of, along with that helm wire). But the instruments stayed on just fine (natch).

So, today we decided to take the boat out again. Our goals were threefold:

1) Check area of hull that sits on bunks to see if it needs extra cleaning (we washed a bunch of slime off the rest of the boat bottom after hauling, but couldn't reach the bunk sections).

2) Burn up the rest of our ethanol fuel, then put in some Ring-Free'd and Stabiled "pure" gas that we'd purchased in town and brought along in a 5-gallon jerry jug; run that through all the hoses and both engines; and then fog both engines.

3) See if we could figure out something on this vexing electrical problem! I did not want to put the boat to bed "broken."

The weather is still just lovely here: Cool nights, days in the low 70's, calm winds and glassy seas, and very clear air. So not exactly a hardship to go out for the day. Still, I was nervous to add an "extra" launch and retrieve (especially since our previous retrieve had gone so well), but.... I guess that means I need the practice!

Electrically, you may remember, we had decided to "encourage" the problem to happen by putting in smallish fuses - one new fuse positioned in the helm feed wire with a 5 amp in it (we only used the basic three instruments), and one new one in the "main fuse" position (10 amp). We didn't use the trim tabs since they had already been cleared of suspicion and we wanted to keep it simple.

We shoved off around 1 p.m. and motored all around Wahweap Bay. Still quite a bit of fuel, so mext we toodled over to the dam, which my buddy had not seen. All this time, electronics bright as day. Sheesh. Then, on the way back, I started thinking out loud again....

"So wait, thinking back, not only has this never happened when we were underway, bouncing along and just moving the way one does; but I think it's actually always happened when the engine is off. At least, five of the six times I'm sure it was off; the sixth one we had just shoved off from a beach and I didn't see it had happened until after I started the engine, but it very well may have already blown and I just didn't notice, as I was looking back at the engine/beach/indicator stream."

"So what always happens when the engine is shut down and we are stopped for a while?" "Things could cool down.... but then the last two times we had only shut off the engine for a minute or two.... not much time to cool yet." "What doesn't happen when the engine is running and thus keeps it from happening?" "If it is the ACR.... how could that play in?"

We decided to pull into a quiet cove on the way back from the dam and shut down and just drift, and see if it would happen. We did that and my buddy, who was growing ever more suspicious of the ACR, decided to go check the status light on it (it shows different patterns for combined, for isolated, for "locked out" (if batteries get down to 9.5V or less), and for start isolation (of house loads*). After we shut down, my bud checked the light. It showed "combined." This is how it should be because it combines when running (charging), and doesn't isolate until it sees a drop to ~12.75 volts (then it isolates to protect the start battery) -- having just stopped, we were still above that.

Just at about that point a (mental) light bulb went on: What if this happens at the moment that the ACR goes to isolate? That fits with the pattern of it always happening after we shut down and are just sitting around in calm water. The times it takes 2-3 hours could be when we stopped with the batteries fully charged (12.9 or so) and/or are not drawing much; and the times it happens quickly could be either when the batteries were not quite fully charged, and/or when we were drawing more (say, charging that laptop in the cigar lighter, or the trim tab retractor cycling - back before I de-activated it). Then the voltage could either be at or below 12.75 -- or get there quickly.

So there we were, drifting in a quiet cove, and the batteries were still higher than 12.75. With our "small fuses to test" program, we couldn't really draw much out of them to hasten the process. We thought about going back to larger fuses and running loads, just to hurry things along, but then decided, no, let's not change more variables. It was a pleasant afternoon to be out anyway. After a while longer... "snick," off went the VHF (and the GPS and the depth sounder; it's just that the VHF makes a sound as it shuts off).

We checked the ACR light.... it was showing "locked out." The main fuse was blown. The (new) helm wire fuse was not blown. Of course after we thought about it for a minute we realized that with the main fuse blown, of course the ACR would see no volts, so would give us the "below 9.5V" lockdown state. When we put a new fuse in, the ACR starts out "isolated" (vs. switching itself to isolated) and does not blow the fuse. Hmm, okay, we may be onto something here.

So okay, now let's motor around a bit and then stop again to test our theory. We motor around, all is fine. The ACR goes to "combine" as soon as we start the engine and it detects charging (because the start battery is basically always full). We motor along a bit and then stop again. This time my buddy goes and watches the ACR light like a hawk. I watch the battery monitor to see where it stands relative to 12.75 (which is when the ACR is supposed to go to isolate status again).

This takes awhile since we're not drawing much with just the instruments, but that's okay, it's a nice day and I'm squaring things away in the cabin and making notes on what we're doing. Buddy is munching on butter candies while he hunches over the lazarette with a small mirror (to see the light on the ACR better).

The voltage finally gets down to 12.75, and I'm just saying "Well, it's about time for...." when "snick!" off goes the VHF (and the GPS and depth sounder), the ACR goes to "lockout" and the main fuse blows. Okay, we have information now!

So next we disconnect the ACR and run that way. Over the course of the late afternoon we run and stop, run and stop quite a few times (once at a beach to clean the hull where it's on the trailer bunks; numerous times to put pure gas in the tanks, run the Honda, etc.). (Side note: If you *really* want to feel like your boat is fuel efficient, then take it out with two tanks at 1/8 full and try to run it out of fuel on purpose. Sheez, we were retrieving in the dark!).

There was one more thing I wondered about: How does the fact that the boat sat on the trailer for two days with the instruments on, and the ACR connected, and nothing blew fit in? Okay, I think we have made sense of that: Since it was disconnected (un-wired) when we hauled last time, the ACR was already in its isolated stage (automatically, so to speak). Then we reconnected it, but because then the engine was never started, it never sensed the start battery charging back to full, and so never combined. Thus, it didn't ever actively "switch over" to isolated mode (which is the moment it seems to blow the main fuse).

Anyway, with the ACR disconnected, everything runs like a top. No fuses blow. I think we have an ACR problem. Tomorrow morning I'm going to call Blue Sea, the manufacturer, and discuss it with them. I'll describe how I have it wired (which I believe is how they recommended I do it, but.... I want to make sure I didn't make a mistake), explain what's happening, and see what they think.

I have apologized to the cigar lighter and the helm feed wire

Sunbeam

*Which, to my chagrin, I found out is optional, and I did not have hooked up - that's on the to-do list.

PS: To the good, now that I have learned more - thanks to the helpful and knowledgable Brats who have contributed - I'm going to put in a larger/new helm feed wire, add enough fuse block(s) to eliminate as many inline fuses as possible, and just generally clean up the behind-the-helm wiring.

[C-Nile]

Sunbeam -- that is a great write up. After my boat accident, I drove the boat back to port for the twenty-mile trip on my kicker engine while running my radio, radar and chart plotter on house battery. After the boat was repaired, we took it out for a ride, and then the chart plotter screen began to dim. The water faucet flow was way down. I scratched my head. The Blue Sea Systems ACR does not charge the house battery when it hits 9.5 volts. I had to disconnect the battery cables to the house battery, flip the battery switch to combine batteries, restart the engine, and all electrical systems ran off of the cranking battery. But for an ACR to blow a fuse -- that is an entirely different matter and something useful to know. I think all of us using Blue Sea Systems ACR's would be very interested to learn about the the cause of your problem.

Rich

[Sunbeam]

[AK Angler]

Sorry this took so long. (Sometimes life overrides good intentions.) But, I'm glad to hear you may have found the problem.

Anyway, I did finally get a chance to draw up (what I think is) your wiring schematic. Before I make any comments/statements, let me know if I got everything drawn up correctly...

[Sunbeam]

[AK Angler]

OK - Here's an updated drawing. I hope it helps clear up how the switch works. (And I added the HPU.)



Basically, when you turn the switch to the 'ON' position, both the start and the house circuits close, and both circuits become hot. The house battery connects to the house side, and the start battery connects to the start side, but they remain separate from each other. In this case, the ACR acts as the 'COMBINE' leg of the switch, sensing the battery voltages and allowing the alternator to charge the start battery, the house battery, or both, as needed - automatically.

When you turn the switch to the 'COMBINE' position, the 'ON' circuits remain closed (hot), the cross-link closes in the switch, and both batteries (in parallel) power both circuits together. In this case, the ACR is - for all intents and purposes - doing nothing.

Does that make sense?


And, of course yo can save a copy of the wiring diagram. After all, it's only relevant for the wiring on your boat.

BlueSea may want to look at it as well...