Tilt Trim goes up by itself

[rf246_sid]

2001 150 HPDI
Tilt/trim has recently started to go up by itself occasionally. Did a visual inspection of the wiring in the controls at the helm and the switch on the motor. No sign of wear on any insulation or breaks that would let in moisture.
Seems to happen most frequently after running at higher speed for a while then slowing down. Like maybe something is heating up to cause the behavior???
Reading other threads has lead me to suspect the relay getting flaky. Since the problem is so intermittent, it is hard to catch it in a failing state. When it happens, i can still control via the helm switch and override to push the trim back down. It typically has only behaved like this for a couple minutes, then is ok again.
Looking for suggestions on how to home in on the culprit.
Thanks.

[jb123]

More likely one of the switches, unhook one at a time to isolate

[boscoe99]

Common issue in the throttle mounted trim/tilt switch.

I am surprised actually that you got 13 years of of use out of your switch.

Replace the expensive relay if you wish. When that does not fix the problem you can then replace the switch.

[rf246_sid]

...i'm looking to AVOID that relay replacement! Will check out the switches.
Thanks,

[TownsendsFJR1300]

It can also be the trim switch at the engine (outside the cowl), but the control switch, as noted, has been failing more often than the engine trim switch..

[boscoe99]

Disconnect the motor mounted trim switch. See if the problem goes away or stays.

If the problem stays then you can focus on the throttle switch.

If the problem goes away, but returns when you reconnect the motor mounted switch, then focus on the motor mounted switch.

I am guessing that it is the throttle switch given that this is usually what it is and given that Yamaha has updated that switch on at least one occasion to try and combat moisture ingress.