Fuel Gauge Problem
Le Mans Master
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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Pro
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From: Ventura County CA
I also thought to put power to the lower connector and ground the ground post and see if it gets hot without going to the sender.
Le Mans Master
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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From: Ventura County CA
Put power to the bottom tab and connected the ground and, nothing.
Checked the sender wire and it goes to ground???
I don't think that is supposed to happen or is that how the tank sender works?
Le Mans Master
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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The ohms wire goes from the gauge to the sending unit in the tank.
A variable resistor changes as the float goes up or down and its all connected to a ground.
A variable resistor changes as the float goes up or down and its all connected to a ground.
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From: Ventura County CA
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
I'm sorry, I've been on vacation killing lobsters in Maine... lol..
So.. lets to a fundamental test
With the key on, pull the ohms wire off the sender.... When you do this the gauge should go to full.... Next take the ohms wire from the sender and ground it out... the gauge should go to empty.
If this works as pictured below, the issue is most likely in the sender... if the gauge doesn't function this way the issue is the gauge. The picture below should help you figure out the issue.
Willcox
So.. lets to a fundamental test
With the key on, pull the ohms wire off the sender.... When you do this the gauge should go to full.... Next take the ohms wire from the sender and ground it out... the gauge should go to empty.
If this works as pictured below, the issue is most likely in the sender... if the gauge doesn't function this way the issue is the gauge. The picture below should help you figure out the issue.
Willcox
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Pro
Joined: Jun 2014
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From: Ventura County CA
I'm sorry, I've been on vacation killing lobsters in Maine... lol..
So.. lets to a fundamental test
With the key on, pull the ohms wire off the sender.... When you do this the gauge should go to full.... Next take the ohms wire from the sender and ground it out... the gauge should go to empty.
If this works as pictured below, the issue is most likely in the sender... if the gauge doesn't function this way the issue is the gauge. The picture below should help you figure out the issue.
Willcox
So.. lets to a fundamental test
With the key on, pull the ohms wire off the sender.... When you do this the gauge should go to full.... Next take the ohms wire from the sender and ground it out... the gauge should go to empty.
If this works as pictured below, the issue is most likely in the sender... if the gauge doesn't function this way the issue is the gauge. The picture below should help you figure out the issue.
Willcox
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Le Mans Master
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
The gauge tested good so how about installing the gauge in the canister and with a fused jumper apply 12 volts to the bottom terminal and see what happens.
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From: Ventura County CA
All tests were done while the gauge was in the cluster and grounded to the cluster. Ground was supplied by the temp gauge. The temp gauge and the fuel gauge were the only gauges/lights in the cluster that were connected.
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Well my next advice would be to pull the ohms wire off the sender and take an ohms reading off the stud.
A follow up test would be if you have an old turn signal flasher laying around you can run one wire from the flasher to ground and the other to the sender wire.
Normally a flasher will have around 50 ohms on it (you can check this before you do this test to know exactly what ohms the flasher is reading) then when installed this flasher to the sender wire you should have just above 1/2 a tank showing on the gauge. This will let you know for sure the issue is the sender and not the gauge.
Willcox
A follow up test would be if you have an old turn signal flasher laying around you can run one wire from the flasher to ground and the other to the sender wire.
Normally a flasher will have around 50 ohms on it (you can check this before you do this test to know exactly what ohms the flasher is reading) then when installed this flasher to the sender wire you should have just above 1/2 a tank showing on the gauge. This will let you know for sure the issue is the sender and not the gauge.
Willcox
Last edited by Willcox Corvette; Jul 17, 2018 at 05:04 PM.
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From: Ventura County CA
Well my next advice would be to pull the ohms wire off the sender and take an ohms reading off the stud.
A follow up test would be if you have an old turn signal flasher laying around you can run one wire from the flasher to ground and the other to the sender wire.
Normally a flasher will have around 50 ohms on it (you can check this before you do this test to know exactly what ohms the flasher is reading) then when installed this flasher to the sender wire you should have just above 1/2 a tank showing on the gauge. This will let you know for sure the issue is the sender and not the gauge.
Willcox
A follow up test would be if you have an old turn signal flasher laying around you can run one wire from the flasher to ground and the other to the sender wire.
Normally a flasher will have around 50 ohms on it (you can check this before you do this test to know exactly what ohms the flasher is reading) then when installed this flasher to the sender wire you should have just above 1/2 a tank showing on the gauge. This will let you know for sure the issue is the sender and not the gauge.
Willcox
There is 1.2 Ohms resistance which is probably caused by using probes. It is really 0 resistance, essentially grounded out.
Too bad since it is a new sender.
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
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From: Ventura County CA
The ohms connector on the gauge goes to ground? Is this correct?
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Coat hanger moves the float up and down and the reading on the gauge corresponds to the float level.
Gauge connections stay cool.
Release the float to empty and the gauge connections (pink +) (Ground -) get real hot real fast.
Gauge connections stay cool.
Release the float to empty and the gauge connections (pink +) (Ground -) get real hot real fast.
Le Mans Master
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Time to remove the sending unit and find out why it does that.
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The sender must be shorting out to cause that, because o ohms is o ohms... no resistance. This wouldn't play any part in wires getting hot unless the sender itself if shorting out when empty.
Willcox
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From: Ventura County CA
Will test the takeout. Shame since it's new.