1984 Jeep CJ-7/New Radio/Gas Gauge Is Going Bonkers

CJM1971

Member
Joined
Jan 24, 2017
Location
Raleigh, NC
Morning, time to reach back out to the big brains on this stuff. My wife had a new radio installed in my Jeep to surprise me for my birthday. She used a reputable place here in Raleigh, and they did a good job, but now my gas gauge is acting funny. Before the Jeep went in I had just recently replaced the sending unit so the gas gaauge would work again, which it was. Now, since the radion install, when I turn the Jeep on, the fuel gauge needle immediately jumps to full and is buried at that mark when before it never really showed a full tank, or was buried on 'F' when it was full....hope that makes sense. I would think if they jacked up the voltage on the sending unit, it just wouldn't work, so I guess I'm asking if anyone has had this issue before, and if so, what was your fix? My guess is most replies will be 'take it back to the radio place and tell them to fix it' which I plan on doing, or at least have them re-check the wiring, but maybe they just bumped a wire to the gauge on install.
 
Did it have an aftermarket radio before? If no, maybe they spliced into one of the fuel gauge wires for the radio and messed it up.
 
It did have an aftermarket radio in it already, I'm thinking they spliced into one of teh gauge wires to get power and pulled a wire when they were reching up behind that dash, it's like sticking your hand in a bowl of spaghetti back there
 
If it's like the 79 & older models, the fuel gauge is powered off the temp gauge. And may be positive ground. Can't recall for sure. But if you just Touch the fuel gauge wires Wrong, for a split second, It's Fried. Sound like a problem! Any idea how much fuel you really have?
 
Could have screwed up the ground as well
 
So would the gauge be fried or the sending unit....and I do recall someone telling me the wiring back there is extremely sensitive, kind of surprising for a vehicle that was built to have the snot knocked out of it, but thank you
 
if a gas gauge pegs at full its a ground issue. (in my exp currently working on the same issue)
 
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