Analog Trim Gauge Stuck Up - Not Working

[natrix19]

Hi Guys,

I have a 2012 Merc Pro XS 225
S/N: 1b863739

I have analog gauges and currently my trim gauge is stuck in the full "up" position. This happens whether the boat is on or off. I'm looking for some guidance to help troubleshoot if it's the gauge, or a bad sender.

I found an old post talking about disconnecting a brown/white wire and turning the key on and seeing if the gauge moved, but my gauge doesn't have any brown wires. It yellow, purple, black, and a 4th color I'm forgetting right now...

It was working fine until recently when I had the oil pump and compressor replaced. So not sure if that's related, or if it's possible something was disconnected during that process. I haven't removed the sender from the motor yet, just looked at it while it was attached and the wires look intact.

Any tips you can provide to begin troubleshooting this before buying a new sender would be great.

Thanks!

-Nate

[EuropeanAM]

Need to check the wiring connections for the trim sensor inside the cowling (right there at the oil pump).

If you have a 3-wire sensor, that's a SMARTCRAFT (digital) sensor (Yellow, Blue and Black wires).

[natrix19]

Thanks for the advice.

I went out and looked for the wiring connections you mentioned and I found the yellow, blue and black wires you're referring to and it didn't seem like they were ever connected to anything. They're capped off, so I don't think I have SMARTCRAFT gauges.

Here's a pic of the wires I found, plus the front and back of my trim gauge (this is with the power off)

smartcraft-wires.jpg
gauge-front.jpg
gauge-back.jpg

When I was looking around inside the engine area for any disconnected wires, I did find this brown/white striped wire that wasn't connected to anything. I didn't see anything that this would go to tho.
brown-wire.jpg

Also, I found this disconnected wire in the transom that runs up to the front somewhere, never found where it comes out. I also never found the male end of this wire anywhere in the transom, but maybe I need to look harder lol. So I'm not sure what this goes too, possibly old electronics from the previous owner?
mysteryplug-1.jpg
mysteryplug-2.jpg

Just for kicks, I've included a pic of the starboard side of the motor, and the trim sender on the port side, in case that helps us troubleshoot.
engine-starboard.jpg
trim-sender.jpg

Thanks again for the advice. Please let me know what I should try next or if any other pics will be helpful

-Nate

[natrix19]

UPDATE: After that last post, I noticed there was a brown/white striped wire in that collection of wires by the oil pump. I plugged that into the loose brown wire from the other pic and turned the key on. The trim gauge did NOT move. I moved the trim up and down a bit, and again no change.

So that didn't seem to fix it, but maybe I did something wrong?

[EuropeanAM]

Try something simple: On the HARNESS side, jumper from the brown w/white stripe wire to the bare aluminum of the air handler. You're GROUNDING the wire.

Turn key on.

Gauge should now show DOWN.

If your results match: Check the GROUND STRAP for your midsection (located at the left side, lower engine mount NUTS, often broken by an engine support with worn sockets).

[natrix19]

Ok, so I made a jumper and jumped from the brown/white striped wire on the harness side to the air handler and the gauge DID go down. :)

Next, I checked the ground strap you mentioned. I wasn't 100% sure what you meant exactly, but I THINK you meant the little braided wire under the nut that the MotorMate sits on. That braided wire appears to be intact on both the nut and on the bracket. Didn't see any fraying or anything (See pic).

[EuropeanAM]

Gotcha. Sounds like your trim sender has failed (just to be sure... perhaps remove the short black ground wire from it's securing screw, clean the ground and re-attach).

New replacement senders have a long ground wire that attaches inside the cowling (to bypass this common "poor ground" scenario).

[natrix19]

Thanks for the advice. I'll give the ground screw a try tomorrow.

Assuming the sender needs to be replaced, are there any tips or issues I should be aware of for that process?

Thanks again!

[EuropeanAM]

Nothing specific, other than to trim the engine up so you can set the safety latch, and remove the STB side lower cowling to aid in getting the wires through.

[natrix19]

Thanks. I was planning on taking off the lower cowling to clean the strainer.

I saw the sticky thread on that, so hoping that goes smoothly