Fuel Gauge
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
Team Owner
Joined: Jan 2003
Posts: 20,322
Likes: 249
From: Summerland B.C. Canada
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
I'm not specifically familiar with the 84 vintage as I have a 94 type vintage. But I would be surprised if there was as fuse associated with the sending unit and the read out assembly.
However there has to be some voltage to the sender on the top side of the wiper. Don’t know what the sender connects back to on the 84 but if it comes from a unit like a CCM, there has to be either a 5 or 12 volts to the sender. Whatever makes the measurement of the fuel senders position (resistance), a current has to be measured and you need a voltage to produce a current.
If someone actually has a schematic of the circuit, that would take a lot of the guess work out of it.
However there has to be some voltage to the sender on the top side of the wiper. Don’t know what the sender connects back to on the 84 but if it comes from a unit like a CCM, there has to be either a 5 or 12 volts to the sender. Whatever makes the measurement of the fuel senders position (resistance), a current has to be measured and you need a voltage to produce a current.
If someone actually has a schematic of the circuit, that would take a lot of the guess work out of it.
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
I'm not specifically familiar with the 84 vintage as I have a 94 type vintage. But I would be surprised if there was as fuse associated with the sending unit and the read out assembly.
However there has to be some voltage to the sender on the top side of the wiper. Don’t know what the sender connects back to on the 84 but if it comes from a unit like a CCM, there has to be either a 5 or 12 volts to the sender. Whatever makes the measurement of the fuel senders position (resistance), a current has to be measured and you need a voltage to produce a current.
If someone actually has a schematic of the circuit, that would take a lot of the guess work out of it.
However there has to be some voltage to the sender on the top side of the wiper. Don’t know what the sender connects back to on the 84 but if it comes from a unit like a CCM, there has to be either a 5 or 12 volts to the sender. Whatever makes the measurement of the fuel senders position (resistance), a current has to be measured and you need a voltage to produce a current.
If someone actually has a schematic of the circuit, that would take a lot of the guess work out of it.
Try measuring voltage at the fuel tank. If no voltage then disconnect sending unit pink wire (unplug 3 wire connector) and measure resistance of sending unit to make sure it is not open cct. Do not measure resistance with wire connected to cluster as this could damage the solid state circuitry.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
There is NO power to the sender....Its as simple as simple can be. One wire to the coil contact, grounds are thru the frame. The whole assy only has 3 wires, 2 of which go the the fuel pump.
Please do not try to "jump" the wire to the sender....in theory the tank cannot explode but another theory that I heard says it WILL when you turn a small coil into a glow-plug submerged in gasoline...there IS a ground...so don;t supply a pos source.
Its just one wire...believe me, I've been in there 20 times.
Please do not try to "jump" the wire to the sender....in theory the tank cannot explode but another theory that I heard says it WILL when you turn a small coil into a glow-plug submerged in gasoline...there IS a ground...so don;t supply a pos source.
Its just one wire...believe me, I've been in there 20 times.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
Thats because this is not just a resistor. There are resistors involved but the intank unit is more of a potentiameter....rheostat in reverse. Float arm moves a contact across a coil. The position of which changes the resistor (variable resistor) value that becomes the signal that you see on the dash gauge.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Potentiometer or rheostat can be the same physical device but only differ in configuration or circuit connections. That is not an issue here.
Three wires;
1 for the common ground for both fuel pump and sender unit.
1 wire for fuel pump power…and
1 wire for sender unit connected in a rheostat configuration
This is not magic. This is an DC electrical circuit and electronics work on voltage. And with that is the associated basic ohms law of voltage, current and resistance. You need to have a potential across the rheostat and that will produce a current. There's no getting away from it.
But if you made the measurement at a empty or near empty tank condition, then the voltage would be minimal because the top end of the rheostat is at ground potential therefore no (or minimal) voltage might be measured. (Got a good ground for the meter).
I have measured on my 94 and with the sender un-plugged it measures 11 volts. And with the sender connected there is approx 2.4 -2.5 volts across sender with a basically full tank.
Three wires;
1 for the common ground for both fuel pump and sender unit.
1 wire for fuel pump power…and
1 wire for sender unit connected in a rheostat configuration
This is not magic. This is an DC electrical circuit and electronics work on voltage. And with that is the associated basic ohms law of voltage, current and resistance. You need to have a potential across the rheostat and that will produce a current. There's no getting away from it.
But if you made the measurement at a empty or near empty tank condition, then the voltage would be minimal because the top end of the rheostat is at ground potential therefore no (or minimal) voltage might be measured. (Got a good ground for the meter).
I have measured on my 94 and with the sender un-plugged it measures 11 volts. And with the sender connected there is approx 2.4 -2.5 volts across sender with a basically full tank.
Last edited by pcolt94; Apr 20, 2011 at 04:40 PM.
Team Owner
Joined: Jan 2003
Posts: 20,322
Likes: 249
From: Summerland B.C. Canada
It's obvious I'm no electrical guru,
my comment was based on reading the FSM's panel connector pinout info. I see now that the info is with panel removed, so that's why they list 0-90 ohms and no voltage.
When I think about it, my meter uses it's battery current to test resistance, so it only makes sense for the same to apply here.
my comment was based on reading the FSM's panel connector pinout info. I see now that the info is with panel removed, so that's why they list 0-90 ohms and no voltage.When I think about it, my meter uses it's battery current to test resistance, so it only makes sense for the same to apply here.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
There is a voltage but it is part of a resistance bridge circuit. It is not directly connected to 12 volts but across a 4 resistor bridge. If it was directly connected at 1 ohm it would draw 12 amps.. E=IR....