1972 cst k5 fuel gauge prob

[brodykelly]

i recently purchased a 72 cst K5 air,tilt, all original body panels with no rust, any way i'm new here and was wondering if anyone has had this problem, my gas guage reads 1/4 tank when full, the guy i got it from said he installed new sending unit from lmc and the new one did the same thing so lmc sent him another one and it also does it, he gave me the 1st new sending unit and the 2nd new one is in it, and the box even says 69-72 blazer sending unit on it. it's not that big of a deal but when you put 35 dollars in gas in it and you drive away and it reads 1/4 it just sucks, any ideas out there maybe guage or ckt bd any suggestions greatly appreciated. thanks brody p.

[Dan72cst]

I haven't had the problem myself, but I heard others say to check the ground wire as it needs a clean connection

[brodykelly]

is that the ground wire on the tank or on the back of dash?

[jhow66]

Look on the back of your gauge and you will see a small white ceramic block that fits over the gauge studs. (it is called a "shunt") This should read about 82.5 ohms (+ or -)--if not gently clean both sides and recheck--if still no go replace it with one from another gauge or you can order one from this place for $7.95--www.fix-a-gauge.com -- just fixed one in a 72 Cheyenne that was doing the samething.(tried new sender -checked wires and grounds etc. before finding problem.) Remove shunt before checking as it will read thru gauge if checked installed.

www.fix-a-gauge.com

[brodykelly]

thanks for the reply will look at the shunt this weekend, i checked the ground yesterday on the tank and it was fine, just got back to see, jhow66 suggestion on the shunt, will check and let you know if it worked thanks again brodyp

[blazerslave]

What's the condition of your circuit board? My bad gauge had damage to its' circuit board and I could never get it to register.

[brodykelly]

the ckt board looks good i was able to reach up behind the dash and get the nuts off the shunt but there wasn't enough play in the ckt bd to get it off so i could remove the shunt and measure the resistance, i did measure it in the ckt and it read 37.5 ohms, which i know i need to measure it out of the ckt. i tried to remove the screws on the outside of the dash bezel and removed the plate under the steering column and removed the knobs and nuts on the wiper and manual throttle lock but the dash bezel would not budge, i was hoping to replace the bezel with a new one i bought and remove the shunt and measure at the same time but i can't get it out what am i missing???? thanks brody p.

[jhow66]

Did you disconnect the speedo cable--oil pressure gauge line?

[brodykelly]

no i didn't, thanks. i'll try this weekend also is there a trick to getting the light switch out, the knob comes off but the switch doesn't have a nut on the outside like the wiper and manual lock, i'm learning more and more everyday thanks any more input is appreciated, brody p.

[jhow66]

Light switch does not have to be removed just the knob and rod plus the chrome bezel--if you can't unscrew the switch bezel with your hand there are 2 holes in it that you can insert 2 picks in aand use a screwdriver between the 2 to turn it off.