clean power weirdness. 225 Prox 4s

[thedude]

I went through and re-did 10 years worth of wiring mess in the bilge area. I had 4s repower in may of last year. Nearly all of the rewiring was moving accessory wires to not be a giant birds nest and relocating my power pole pumps.

after i had everything hooked back up, i was not getting ignition signal to power on my main relay bus and no tilt trim (no beep or anything when turning the key either, didn't hear fuel pump). I've disconnected everything from the battery and completely isolated only the clean power connection and main battery +/- wires to my battery at this point.
I keep reading 21-24v when reading the voltage on the clean power terminal. I can even disconnect it completely and it will show the same voltage between the 2 disconnected wires at 20+ volts. From the disconnected ground of the clean power to the + bat terminal, it will read 12v (clean power still disconnected).

With only main terminals and clean power wired up, i checked voltage at my ignition between the +/- pins and it was showing 24~v there also.

I have since disconnected the large round controls connector also and same results (not to ign obviously) but no tilt/trim using the trim switch on the chasis.

From my understanding of the clean power harness's purpose, i don't think i should be seeing voltage (let alone 24v) when its disconnected. Not sure where to look from here. I will call my dealer, but looking for any insight as the motor is currently trimmed down and i can't tow it anywhere the way it sits until i at least get the trim working.

I've also checked that i have 12v at the main power lugs on the front drivers side under the cowling and that all the fuses on the port side front are good. I read 12v on the fuel system fuse, the rest 0.

[EuropeanAM]

You should NOT be seeing 24V there. YOU HAVE ANOTHER BATTERY TIED INTO THE WIRING (IN SERIES) SOMEHOW.

Clean Power harness should connect DIRECTLY to the Cranking Battery (not to buss-bars, battery switches, or other devices).

[thedude]

there was physically no other battery in the boat (so you can imagine my confusion). I did figure it out though. the fuse on clean the power blew, sort of... it had continuity so it buzzed with meter but measured 24+v on the motor side and 12v on the battery side. replaced fuse and everything works. i wouldnt have known had i not visually inspected it and noticed the filament just looked out of shape. i assume the 24v has something to do with reading a nominal voltage backfed from the PCM and using the battery terminal as a ground (assume clean power has some sort of isolation circuit in play).

[EuropeanAM]

Was the engine RUNNING when you found 24V on the engine side?

If not, there be "ghosts" in that wiring!

[Pulsare2020]

there was physically no other battery in the boat (so you can imagine my confusion). I did figure it out though. the fuse on clean the power blew, sort of... it had continuity so it buzzed with meter but measured 24+v on the motor side and 12v on the battery side. replaced fuse and everything works. i wouldnt have known had i not visually inspected it and noticed the filament just looked out of shape. i assume the 24v has something to do with reading a nominal voltage backfed from the PCM and using the battery terminal as a ground (assume clean power has some sort of isolation circuit in play).

I am trying to figure out how that can happen but it appears beyond my pay scale. I assume the voltmeter was on the DC and not AC function as I have made that error once. You have one 12V battery so where does the 24V come from? I'm sure no battery charger was connected, no shore power was connected or you would have mentioned it? I am trying to learn here. Are you saying the PCM can increase the battery voltage to 24 for some functions and that was what you thought you were reading? I thought the PCM uses 5 volts for most monitoring functions but certainly could be wrong. Glad you noticed the out of shape filament and got it working again.

[bloodman]

Wow...an explanation of the 24v thing would really be nice. Good job figuring it out!!

[EuropeanAM]

Only explanation I can think of (other than a second battery in the system) would be that the alternator had full-fielded due to loss of battery connection (similar to what happens when the fusible link lead burns out), and the engine would have to be running, too.

[thedude]

It was not running. I spoke with my dealer while trouble shooting and he mentioned blowing the fuse link on the alternator line if the main power cables were crossed and how that can cause a 24v reading and how to test it - the impedance test was ok on that.

Not being familiar with the circuitry in the clean power loop, its not unreasonable to see voltages other than 12v coming OUT of a pcm. I used to do automotive digital circuit QA testing for engine controllers - reference voltages used in the pcm can be anything, especially if they are used as a sensor value. It wouldn't be out of the question for multiple capacitors or resistors in the circuit to show odd voltages if the pcm was shut down.

I don't think there's any gremlins in the wiring, i think if you hook up that engine with the primaries and clean power only directly to a battery - and disconnect the positive clean power from the battery, you will see that voltage in the same places i did. There was absolutely nothing else hooked into the system in any way when i was reading those voltages. I even disconnected all the controls from the main harness - so just the primaries and the clean power to a battery and that is it. motor has like 5hrs on it and is basically new.

if anyone is feeling curious i would love to know if that was the case :)

[thedude]

i'm making A LOT of assumptions obviously - if you have a meter and 4s merc, pull the fuse on the clean power positive line and read voltage from the bat (-) to the engine side fuse terminal in the fuse holder. My guess is its a capacitor on that line to provide enough power to shutdown the PCM safely when clean power is disconnected from the battery.

[EuropeanAM]

Just pulled one myself out of curiosity- as expected, NO voltage on the engine side with the fuse removed.

[thedude]

bleh. guess i'll call an exorcist then lol

[Tparkin]

Clean Power harness should connect DIRECTLY to the Cranking Battery (not to buss-bars, battery switches, or other devices).

With the clean power harness connected directly to the battery, is there any sort of parasitic draw on the battery when the main batt switch if 'Off'? Meaning...would there be any draw on the battery when all except the clean power harness is run through the switch?

[Pulsare2020]

With the clean power harness connected directly to the battery, is there any sort of parasitic draw on the battery when the main batt switch if 'Off'? Meaning...would there be any draw on the battery when all except the clean power harness is run through the switch?

There is a small parasitic draw on mine, around 150 - 250 milliamps even with the battery switch off. The clean power harness does not go through the battery switch. I measured mine a few times since I suspected an even higher parasitic draw than I measured. At the time, I felt that my battery lost more voltage when the boat sat for 3 weeks than it should have.

[Tparkin]

There is a small parasitic draw on mine, around 150 - 250 milliamps even with the battery switch off. The clean power harness does not go through the battery switch. I measured mine a few times since I suspected an even higher parasitic draw than I measured. At the time, I felt that my battery lost more voltage when the boat sat for 3 weeks than it should have.

That's what I was curious about. I'm repowering with a 4s that has the clean power harness and it seemed odd to have a direct connect to the battery at all times. I assume there is no "real" draw until the ignition circuit is active but I don't know. If its the equivalent of leaving an accessory on, seem like it would be a problem. I guess I would rather know ahead of time that to end up with a dead batt at some point.

[EuropeanAM]

That's what I was curious about. I'm repowering with a 4s that has the clean power harness and it seemed odd to have a direct connect to the battery at all times. I assume there is no "real" draw until the ignition circuit is active but I don't know. If its the equivalent of leaving an accessory on, seem like it would be a problem. I guess I would rather know ahead of time that to end up with a dead batt at some point.

Clean power is MANDATORY connection DIRECT to cranking battery- and yes, there is a very nominal (but measurable) draw.

I've not seen any real problems from this, however (keeping in mind that Clean-Power has been used in the DTS models since mid-2004.

[Tparkin]

Clean power is MANDATORY connection DIRECT to cranking battery- and yes, there is a very nominal (but measurable) draw.

I've not seen any real problems from this, however (keeping in mind that Clean-Power has been used in the DTS models since mid-2004.

Got it. Thanks. I was just curious about the possible draw than anything else, it's obviously an non-issue since it's designed that way.