If anyone needs to replace a dead or janky trim position sensor, I did the following. For reference, Unit removed from engine was 3855074 which google says 1999 trim sender 3 wire model # 3855074 replaced by #3849411. The replacement sensor was pretty pricey for OEM and the aftermarket units had some poor reviews.
Only two wires are needed for my setup, so your results may vary. But the internal of the trim sensor is just a potentiometer, my existing one had a broken terminal. Connect your wires to the center and outward terminals of the potentiometer, you need to use the pair that corresponds with a positive increase in ohms from zero corresponding to the rotation of your pivot bolt that the potentiometer shaft inserts into. The little bolt shaped piece slides off the old potentiometer shaft and slides right onto the new one (use some adhesive to prevent slip)
Total sweep of pivot bolt is about 60 degrees from top to bottom of tilt range.
So, a 500 ohm potentiometer will be about 83 ohms of sweep from zero ohms at fully down. Or, about 95 ohms if set to 12 ohms at fully down (per the manual).
A decent 500 ohm potentiometer that appears to be sealed on the wire side is on amazon for a few bucks. https://www.amazon.com/gp/product/B074KBX9RZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1
Pic of torn down sensor with a new 500 ohm potentiometer installed and sealed with RTV: .
This setup set to 11 ohms showed full sweep on my VDO trim gauge. Seems to work excellent.
Only two wires are needed for my setup, so your results may vary. But the internal of the trim sensor is just a potentiometer, my existing one had a broken terminal. Connect your wires to the center and outward terminals of the potentiometer, you need to use the pair that corresponds with a positive increase in ohms from zero corresponding to the rotation of your pivot bolt that the potentiometer shaft inserts into. The little bolt shaped piece slides off the old potentiometer shaft and slides right onto the new one (use some adhesive to prevent slip)
Total sweep of pivot bolt is about 60 degrees from top to bottom of tilt range.
So, a 500 ohm potentiometer will be about 83 ohms of sweep from zero ohms at fully down. Or, about 95 ohms if set to 12 ohms at fully down (per the manual).
A decent 500 ohm potentiometer that appears to be sealed on the wire side is on amazon for a few bucks. https://www.amazon.com/gp/product/B074KBX9RZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1
Pic of torn down sensor with a new 500 ohm potentiometer installed and sealed with RTV: .
This setup set to 11 ohms showed full sweep on my VDO trim gauge. Seems to work excellent.