13 Button OBC adjustment

[carnerd]

Hey, I searched threw the forums as best as I could and could not find a definite answer to what I was looking for.
I swapped the 13 button OBC in my 86' eta. With the correct coding plug from a 84' eta, which I presume would be the same. The problem I'm having is with the fuel remaining adjustment. Ive read that the low fuel light should come on when you get down to 6L. My OBC indicates 6L way before the low fuel light comes on (40 miles).
For testing, I lifted the level sensor out of the tank in till it was no longer submersed in fuel. The low fuel light was solid, but the OBC still displayed 6 liters, even after a key cycle. Not sure how to make this read accurately.
Most people say wait till the light comes on then adjust the screw in till it displays 6.0 liters. But what if its at 6 liters already? If anyone has any advice I'd appreciate it! Thanks! -Phil

[jlevie]

At this point there are three possibilities; the gauge, level warning switch, or OBC. The first task would be to find out if the gauge and level warning are working correctly. Start by checking the sensor's resistance with the float at the top (zero ohms) and at the bottom (I think it should be 56 ohms for this car). The next check would be to verify the level readings and that's best done by draining the tank and adding six liters. The warning switch should be closed and you need to take note of the sensor resistance. Then add about 2 more liters and see if the switch turns off and the sensor's resistance changes. If it doesn't add more fuel two liters at a time and see what happens. If the resistance isn't linearly changing with each two liters added the sensor is bad.That also tells you when the switch trips. Obviously, if the sensor is working properly and does reflect the level changes properly as you add fuel the problem lies in the OBC.