2012 Volvo Penta 8.1Gi power trim issue

[rkfishjr]

My power trim is raising on its own for unknown reasons. Have replaced both up and down relays and the thermal fuse. Disconnected the transom up/down switch, no change resulted. Cannot get to the throttle lever switch because its integrated into the handle. Throttle lever switch seems to work as it will power trim both down and up. As soon as I release the down switch the trim starts coming up on its own. Pump motor is running and trim is moving. What could be causing?

 

[Donald0039]

When it's coming up on its own is the trim pump motor running?? That's important to know.

 

[rkfishjr]

When it's coming up on its own is the trim pump motor running?? That's important to know.

Yes, sorry should have stated the motor is working. Outdrive trims up and down when hitting switch, as soon as you let go of switch it then trims up by itself.

 

[Scott Danforth]

Is the motor running when it trims up on its own. Yes or No?

If yes, you have an electrical issue

If no, you have a mechanical issue on the hydraulic side

 

[rkfishjr]

Is the motor running when it trims up on its own. Yes or No?

If yes, you have an electrical issue

If no, you have a mechanical issue on the hydraulic side

Yes, motor running when it trims up on its own. I agree its an electrical issue.

 

[Scott Danforth]

Yes, motor running when it trims up on its own. I agree its an electrical issue.

then it should be easy to determine where the voltage is coming from. you are limited to the blue wire side of the controls. either your switch is bad and shorted, or your relay is bad and shorted.

 

[rkfishjr]

then it should be easy to determine where the voltage is coming from. you are limited to the blue wire side of the controls. either your switch is bad and shorted, or your relay is bad and shorted.

Here lies the problem. I cannot find what is sending the signal to raise the trim and/or where it is coming from.

 

[Scott Danforth]

take a volt meter. check for voltage on the blue wire feeding the relay. if power is there, its coming from the switch. if no power, check for voltage on the heavy blue wire coming from the relay to the motor. if power is there, its the relay.

 

[rkfishjr]

Still chasing this issue, here's some more info:
1. Have ruled out switches, both are good and working
2. Replaced both up and down relays, no change in problem
3. Found a lose ground cable (yellow) where negative battery cable connects to a grounding terminal bar on the transom. Tightened, no change in problem.
4. Trim only coming up by itself after running the boat for awhile, seems like after everything gets hot then problem appears. Doesn't happen when cold at the dock.
5. Noticing both digital trim angle meter (four winns EVC) and dial trim meter will randomly jump around even when trim is stationary
6. Can hear and feel the trim up relay rapidly clicking/firing multiple times then trim itself will start to trim up on its own.
7. Can lower it down using either then its comes back up again
Definitively feels like really strange electrical issue going on but cannot track it down.

 

[Donald0039]

Kind of sounds like some chafing in the wiring harness. Do you have a wiring diagram? Can you compare wiring diagram vs actual wiring? Don't rule out a previous owner altering the wiring in an attempt to fix something.

Is the entire trim up and down all basic switches and relays, no ECM involved?

 

[dypcdiver]

Sounds as if the clicking relay is getting a very small current that is not quite enough to pull it in with a positive click. Have you checked with a volt meter?

 

[Donald0039]

Sounds as if the clicking relay is getting a very small current that is not quite enough to pull it in with a positive click. Have you checked with a volt meter?

This was when no trim switch is being pressed. Doing this on its own.

 

[rkfishjr]

Kind of sounds like some chafing in the wiring harness. Do you have a wiring diagram? Can you compare wiring diagram vs actual wiring? Don't rule out a previous owner altering the wiring in an attempt to fix something.

Is the entire trim up and down all basic switches and relays, no ECM involved?

I am the original owner so all wiring is OEM. The boat does have the Four Winns ECM system.

 

[rkfishjr]

Sounds as if the clicking relay is getting a very small current that is not quite enough to pull it in with a positive click. Have you checked with a volt meter?

Definitely getting a stray current from somewhere or a short triggering the relay. Cannot find source of the current.

 

[Donald0039]

Definitely getting a stray current from somewhere or a short triggering the relay. Cannot find source of the current.

So there is typically a small spring inside the relay that holds the contacts in the unenergized position. What if the spring broke or became unattached and the the contacts could bounce back and forth going on and going off at random. Longshot.