oil temp combo gauge bench testing, what am I doing wrong (question answered) next: calibrate the gauge Options

[malcolm2]

I have had this gauge for a while. I also found the complete taco plate, sender etc... to set it up. I decided to test it. I tested the sender a while back in hot water and remember getting various readings as the temp increased.

I pulled out my 12v powered drill battery, put 12v + on the + terminal of the gauge and the - on the - of the gauge. ( you can't see the - wire in the picture, but it is there)

The gauge moved to where it is in the picture without the sender even being connected. It did not move once the sender was connected.

Inside the temp gauge are the following #s. Far left 30, at the start of the red line 156.7 and the end of the red line 170 *C

The top of the paper is what is stamped on each face of the hex and the gauge part # has been edited to what you see in the picture.

1. why is the gauge moving at room temp with or with out the sender?
2. do I have this thing hooked up right? any alternate testing suggestions?
3. do I have a matched sender & gauge?

[timothy_nd28]

Sorry, was unaware that the needle was not traveling to the cold mark, thought we resolved this earlier by grounding the sensor's casing. I think your sensor maybe out of tolerance. Let's try bench testing once again, the same way but not with the boiling water this time.

Adjust your potentiometer to 1000 ohms, instead of 0. You should now have a total resistance of 2800 ohms at room temperature (measuring from the sensors' case to the G terminal on the back of the gauge). Power it up and see if the needle moved any closer to the cold position.

[malcolm2]

Sorry, was unaware that the needle was not traveling to the cold mark, thought we resolved this earlier by grounding the sensor's casing. I think your sensor maybe out of tolerance. Let's try bench testing once again, the same way but not with the boiling water this time.

Adjust your potentiometer to 1000 ohms, instead of 0. You should now have a total resistance of 2800 ohms at room temperature (measuring from the sensors' case to the G terminal on the back of the gauge). Power it up and see if the needle moved any closer to the cold position.

it is actually about 3 mm closer to the left WITHOUT the pot in the circuit. I tried it in line then took the pot out, re-connected and it dropped (moved left) a smidge when re-connected.

update: measuring from the sensors case to the G term with the pot in line and the meter on 2K I get .242.

2nd update: I made a circuit from the terminal of the sensor thru the pot (at 1000 ohms) and checked it at room temp. meter on 20K setting, I read 3.2.... remove the pot and I read 2.2. Seems logical.