wiring up fuel gauge

[1shot1yote]

Hi I'm running a late model gas tank in my 83 K10 and a sending unit out of an 04 silverado.  It is my understanding that the ohm output in 04 is 250 empty and 40 full.  Is there any way to wire in resistors and such to make it work with a 0-90 gauge that I already have?  Will I have to buy a different gauge?

[markolson]

I was under the impression that the 0-90 ohm sender is 0 ohms empty and 90 ohms full, which is backwards from your 04 unit.  So using a resistor will definitely not work at all.  But I am a bit surprised that Chevy would change the direction of the senders...

If the 04 sender were 40 oms empty and 250 ohms full, it still would not work very well.  You could run a 140 ohm resistor in parallel with the sender, but that would change the range to 90 ohms full and 31 ohms empty.  So it would be accurate at full but it would register about 1/3 of a tank when empty.

FYI, the formula for resistors in parallel is: 1/R = 1/R1 + 1/R2.

Reducing the size of the resistor gets you a little closer to 0 when empty, but much further from 90 when full.  So regardless, it looks like you need a newer gauge that is compatible with the sender.

[Captkaos]

An 04 sensor is 250 empty and 40 full, you will need to either add a generic sender with the 0-90 values, or find a new gauge.

[1shot1yote]

Thanks that's kinda what I figured.  Would a programmable gauge work with the factory sender or not?

[Irish_Alley]

yes but the sender has to be working.