Trim position sensor testing

[smhamilt]

1998 150 TLRW. When checking the sensor, should the resistance change over the range for both black to pink AND black to orange?

I'm measuring black to pink = 807 to 10 ohm. This reading changes I when I move sensor.

black to orange = 1046 ohm. This reading does NOT change as I move the sensor.

is this sensor bad?

[fairdeal]

what I'm seeing, is that on a three wire sensor,
Pink-Black should vary from 582-873 ohms
and Orange-Black should vary from 800-1200 ohms

[smhamilt]

Thanks the manual is unclear if BOTH should change.

This is an expensive part so I want to be 100% sure.

Can anyone confirm?

[smhamilt]

Got it. The sensor is bad.

Thanks again.

[throrope]

Could be a bad contact or connection due to dirt or salt. A good cleaning with a cold brew may do.

[rodbolt17]

orange is a 5v ref.
pink is a pick off voltage.
black is ground for both.
ohms should not change on orange to black.
your simply measuring a resistor.
myself I would be measuring input and output voltages long before resistance.

[fairdeal]

so the SM is "incorrect" - or at least -

expressed in a highly mis-leading manner

[smhamilt]

orange is a 5v ref.
pink is a pick off voltage.
black is ground for both.
ohms should not change on orange to black.
your simply measuring a resistor.
myself I would be measuring input and output voltages long before resistance.

So, I should see 5V orange to black. And I should see Voltage change on pink to black?

My apologies, I guess I really don't understand how this sensor circuit works...

Thank you.

[rodbolt17]

the tach sends 5V down the orange wire through a resistor to ground.
as the wiper moves along the resistor a voltage that varys is picked off and sent back to the tach via the pink wire.
yes it is that simple.

[smhamilt]

Thanks for that.

So, can someone tell me EXACTLY how to test this device?

[pstephens46]

Post # 7 above. Straight out of the service manual.

What else do you need?

[smhamilt]

Post # 7 above. Straight out of the service manual.

What else do you need?

I need a specific procedure...READ #6 above....which test method is correct?

#6 saying org to blk should not change and manual is VAGUE...

[panasonic]

So, I should see 5V orange to black. And I should see Voltage change on pink to black?

My apologies, I guess I really don't understand how this sensor circuit works...

Thank you.

I can see how you are confused....the manual is misleading or vague as has been said. I would test it as Rodbolt says...measuring voltage with the sensor hooked up...not resistance with the sensor unhooked. So if Rodbolt is correct..which he usally is, try the following and see what you get.

With the sensor hooked up and key on. Use two paperclips and back probe the sensor plug, one paperclip in black and the other in orange...you should see 5 volts (reference voltage from tach) This should not change when moving the sensor arm.

Next switch the paper clip from orange to pink. Between the pink and black you should see the 5 volts changing when moving the sensor arm.

I am "assuming" that you will see a full 5 volts with sensor arm all the way one direction (either up or down) And when the sensor is moved the opposite way the voltage will go down from 5 volts to a lower voltage. I don't know what the minimum voltage would be...Rodbolt didn't say....

This is way I am interpreting what Rodbolt says and what the manual says.

I believe from the resistance readings you gave from your sensor and the way Rodbolt says that the system works....that the sensor is ohm testing OK
but you are not getting the 5 reference volts from your tach OR the tach is not getting the output voltage from the sensor. Could be totally wrong as well...lol

[panasonic]

What happened to Boscoe's reply with the YouTube videos link?

[rodbolt17]

always remember one simple fact, especially with old antiques.
that manual was translated,sometimes poorly from Japanese to emglish.
sometimes it is poor other times simply wrong.
that is where 6 yrs in the USN advanced electronics field comes in a bit handy.