Trim sender, gauge or wiring issues..not working. Where to start?

[Eastboundndown]

Just looking for any input on the best way to diagnose the cause of faulty reading. Tried lowering unit, loosening screws and adjusting the sensor Both directions and gauge never moved from all up position. Was thinking That the next step I might take is to disconnect sensor wires from terminals in engine compartment and try to test sensor for continuity or resistance but I’m really not sure what readings I’m looking for or if there is something else I should troubleshoot first.late 80s 5.7 merc. With Alpha 1. Thx

 

[tpenfield]

the trim limit switch is on the Port side of the outdrive. The trim sender is on the starboard side. I believe the ohms reading should be a max of 170 ohms (+/-).

In all likelihood, it is the wiring that has broken, but that is usually quite visible. Otherwise, the internals of the sender (basically a rotational potentiometer) may have failed.

 

[Eastboundndown]

the trim limit switch is on the Port side of the outdrive. The trim sender is on the starboard side. I believe the ohms reading should be a max of 170 ohms (+/-).

In all likelihood, it is the wiring that has broken, but that is usually quite visible. Otherwise, the internals of the sender (basically a rotational potentiometer) may have failed.

Thank you for the input. Switch is okay. I tested sender today. Took wires off terminal block at engine and had a buddy turning the sender and I was getting readings between 5-140 ohms. Gauge is staying pinned to the up position.. I know it’s hardly ever a gauge problem. I haven’t tested brown wire from block to gauge. Is there a way to test the gauge just to rule it out before I get any more involved with the wires? Thx

 

[achris]

.... Is there a way to test the gauge just to rule it out before I get any more involved with the wires? Thx

Turn the key ON. Verify you have 12v on the purple gauge wire (using the black wire on the gauge as the ground reference). Then with a short length of wire, one end to the gauge black and the other to the gauge S terminal (should have the wire from the sender on it, probably brown/white). Gauge should move to full down. If it does, the gauge is fine.

Chris.....

 

[Eastboundndown]

Turn the key ON. Verify you have 12v on the purple gauge wire (using the black wire on the gauge as the ground reference). Then with a short length of wire, one end to the gauge black and the other to the gauge S terminal (should have the wire from the sender on it, probably brown/white). Gauge should move to full down. If it does, the gauge is fine.

Chris.....

Thx Chris.. that’s what I needed buddy! Will do tomorrow and post results.