Yam Speedo/Fuel Gauge

[Jason2tpa]

Hey boys. Helping my pops with his 2004 F150TLRC. HE's got the old style round gauges. Both gauges lost power, but I got both powered up now. However, the fuel gauge is not correctly reflecting fuel level and it was prior to losing power. The speedo function of gauge works, just not fuel. Perhaps Boscoe can chime in with his fancy wire schematics so I can figure out what wire is feeding what, etc. What is the red wire's function, as it relates to speedo/fuel gauge?

[fairdeal]

the white wire is the power out to the tank level sender
black is ground
yellow is of course ignition and blue the backlight
the speedo also has a "clock"? I imagine that's the reason for red - constant power
although IIRC has been mentioned that its also used to hold the trip distance in memory

[99yam40]

what did you have to do to get power back?
jumper some wiring?
might be the wrong wiring

[Jason2tpa]

Ah man too much too detail...old wiring finally caught up in his rig. Accessory feeds to both gauges were bad...cut out the bad and got power to gauges. Turns out the fuel gauge is working, though im still unsure what the function is of the red wire going into speedo/fuel gauge. It's badly corroded, metered tested 8v on it, yet all gauge functions are operable.

[99yam40]

red is normally 12v+ from battery on yamaha motors,
fairdeal already mentioned some possible things.
replace it too if it is bad