Trim Indicator

[mainexile]

To all who followed my adventure in trying to straighten out the re-wiring done by Previous Owner (PO), the saga continues. As you may recall in the last episode, PO had replaced the bell housing, but he didn't reinstall the trim limit and trim sender switches. I bought new switches and hooked them up last night before permanently mounting and routing wires. Everything worked fine in the trim limit circuit, but the trim sender is a different story. The sender works, but the indicator goes from full down to full up with only a microscopic change in tilt. Obviously, this 78 Mercruiser 470 originally had the old style sender and limit switches to go along with the original trim indicator. My question is: when Mercury changed these switches to the new style, did they change anything in the trim sender that would cause the indicator to deflect instantaneously from down to up and vice versa? I'm guessing that the trim sender is actually a variable resistor that changes the impedance of the trim indicator coil. If that's the case, did Mercury change the sensitivity of the senders, or do I have a bad indicator. I'd rather rule out any other minor problem before buying a nre trim indicator. Suggestions?

Thanks,
Steve

 

[Don S]

Re: Trim Indicator

Sounds to me like you have the trim limit switch in place of the sender. or you have the wires mixed up inside the boat.

 

[mainexile]

Re: Trim Indicator

DonS,

Trim limit is working fine - "out/up" button takes the drive to 21-3/4" extension on the cylinders and "trailering" brings the drive full up. Trim sender is wired properly, and indicator deflects - it just deflects all the way with minimal change in drive angle.

Steve

 

[wire2]

Re: Trim Indicator

Time to test the sender. Remove lead from gauge, put Ohmmeter on lead, place other lead to ground, operate trim. It should vary resistance with position smoothly. If it goes from infinity to 0 Ω or vice versa suddenly, you're connected to a limit switch.

 

[Don S]

Re: Trim Indicator

What does it say on the outside of the sender?

 

[thrasher]

Re: Trim Indicator

this can also happen if you incorrectly install the trim sensor unit. The unit is a variable resistor but if not adjusted correctly the wiper on the variable resistor can come off the end of the carbon resistive coating, causing the resistance to go from zero to almost infinity instantly!! As suggested connect a multi meter across the two leads and try turning the body of the trim sensor and see iff you can get the multimeter to show a gradual change inresistance as you rotate the body. The sensor needs to be on the starbard side of the gimbal ring.

 

[mainexile]

Re: Trim Indicator

Thrasher,

I'm currently at work, but as soon as I get home I'll put a meter on the sender. Later today I'll post the results.

DonS,

The outside of the sender definitely says "Starboard". The new version of these switches can be mounted only one way for proper routing of the wires.

Steve

 

[mainexile]

Re: Trim Indicator

OK guys,

Put a meter on the sender switch and rotated it from one end of the adjustment slot to the other. Read 0.6 ohms at one end and 110.3 at the other with a smooth transition in between. Does that make this sound like a flaky indicator?

Steve