1958 GMC 1/2t truck 302 6cyl stock 12v gauges Installed EZWIRING harness. Put 10gall of gas in tank. Gauge only reads empty. It flickers, when in start, but still reads empty. Replaced sending unit with new. Installed new ground wire for sending unit to frame. dash console ground to frame. Even ran a separate wire to sending unit to the gauge- no difference. what am I missing?
If you have voltage at the tank by removing the ground the gauge should read either full or empty. Then hook the wires from the gauge together and it should read opposite. This will check the wires and the gauge. If that doesn’t work try doing the same directly at the gauge, that will isolate you to wiring or gauge. Sent from my iPhone using The H.A.M.B. mobile app
don't rule out a sunken float if it one of those brass floats. I have had three of them leak. Pretty cheesey
My opinion is the wiring kit, so check ground at ne wwire to frame to make sure it has connection, then remove gauge wire from sender ground it if the ga in the dash go to full all is good,then you have a sender issue or a ground problem, if not make sure ga in dash is getting voltage,if it is there is a good chance that the ga is bad, but check the wire from the sender to the ga to see if it has continuty, this should tell you what part of the system could be haywire.
uh...how about troubleshooting the problem? First, make sure the gauge is getting power to the IGN terminal, when the key is in RUN position. then, make sure the sending unit is functioning properly. Disconnect the SENDER wire from the gauge, and measure the resistance of this wire, to ground. It should read 15 ohms with half a tank of gas. After you do these things, let us know what you found.
I’m following this, as I’m having issues too. Except mine is s Ford, so everything with the fuel sender is backwards.
same rules apply...just that the resistances are backwards. If you measure the resistance of the sending unit wire, to ground, you still want to see something in the 10-75 ohm range.
Yes power to the gauge with key in run position. continuity is good on sending unit wire. ground unit wire- no change. unhooked sender unit wire from gauge - no change . 26 ohms at the sending unit. It already had some gas in the tank; but I added the 10gal Reads empty.
ok on backside of gauge are two terminals not labeled .which is sending unit wire terminal. instrument cluster is ground to the frame.
You can see the blue terminal which grounds the housing and the fuel gauge. The brown wire on the back side goes to the pink sending unit. The pink wire goes to “gauge power”
still not sure what's going on?. I took an old gauge and put wires on the backside& removed the sending unit wire and that gauge went to full. But the one that was in the truck didn't do that. So ordered auto meter 1718 fuel gauge. still not sure if I have a bad sending unit even though brand new....
Once you figure the gauge wiring out, the wiring chart with the kit should tell you which wire goes where, check that, if that is correct or gets corrected just ground the ga wire at the tank sender to see if it goes to full, if so pull the sender out of the tank, ground it hook up the ga wire and move the float if the ga works your in business, if not time for a decent sender. 6 months ago I put a new float on a tank sender on a seat tank Ford truck it never left the shop had 3/4 gallons of gas in tank to start and move,everything worked, last week put the truck on the road to the gas station to gas up and the ga doesn't work, so back to the shop, pull the wire off sender touch to ground ga works,nice, pull sender, this is still an orginal Ford not a shitty repop, friggen cheap ass float has a crack in it and full of gas, brand new float, drained it soldered it and been working fine for a week. As an aside, Jim wasn't there a thread on roll back trucks on the forum sometime ago,I've looked but no can find.
If it is like a gm pass car from that period. With the key on the gauge should show full or past full with the sender wire unhooked- touch the sender wire to ground and gauge should show empty. These are 0 to 30 ohm and can be very sensitive to proper grounding. If the gauge just jumps a bit with key on the gauge is suspect.
if the sender is reading 26 ohms with the tank mostly full, then it's ok. Yes, the gauge should go to past "full" when you disconnect the sender, and it is getting power and ground.
Can you get the 26 ohm reading up at the panel as well? That wire runs up over the top of the door in the channel area of the cab, could be it's worn through and shorted to ground/metal.
As Squirrel mentioned the resistance reading is 'backwards' compared to other makes. However Ford also used an IPVR(instrument panel voltage regulator) that sends out a 5V pulsed reference to the sender. I am not sure when Ford started doing this, so if you are running 12V directly to the sender you can fry the sender.
yeah, I forgot about that! they started the IVR in 56 when they went to 12v system. The regulator actually sends out a pulsed 12v power to the gauges, and the long time constant of the thermal gauges makes it act like they are only getting 5v. But they actually do get 12v, and you can give them 12v, but not for very long, or they'll burn up.
mine runs out the main firewall hole down under the cab then back up under the cab to the sending unit. Getting 26 ohms at the gauge. Ordered a gauge that is 0-30 ohms-
Hi. If it is the gauge with the 2 pink wires on one terminal and a brown wire on the other are those two terminals rotated to where they are touching? If so to be sure loosen one of the nuts and rotate that terminal connecter for better clearance & tighten the nut. Jimmie
The Jalopy Journal
