Fuel gauge testing
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Laughing Gas
Joined: Dec 2014
Posts: 774
Likes: 10
From: Simsbury, Connecticut
Fuel gauge testing
Yes, you all should be able to tell I'm working out a few bugs. I have another one. How do I test my fuel gauge and my sending unit?
The gauge is brand new from Macs. The sending unit was included in the used '56 tank I got second hand. All is now installed but the gauge doesn't work. When I turn on the ignition it pegs at full and stays there. It goes back to empty when I turn the key off but it takes a while. I know for a fact I only have a few gallons in the tank.
I recall a thread I saw some time ago that showed the process but I can't find it.
Thoughts?
The gauge is brand new from Macs. The sending unit was included in the used '56 tank I got second hand. All is now installed but the gauge doesn't work. When I turn on the ignition it pegs at full and stays there. It goes back to empty when I turn the key off but it takes a while. I know for a fact I only have a few gallons in the tank.
I recall a thread I saw some time ago that showed the process but I can't find it.
Thoughts?
Laughing Gas
Joined: May 2010
Posts: 1,125
Likes: 191
From: Wharton, PA
here are a couple links that should help
https://www.ford-trucks.com/forums/979251-fuel-gauge-doesnt-work.html
https://www.ford-trucks.com/forums/1...t-working.html
https://www.ford-trucks.com/forums/979251-fuel-gauge-doesnt-work.html
https://www.ford-trucks.com/forums/1...t-working.html
Senior User
Joined: Mar 2017
Posts: 422
Likes: 28
From: Albany NY
I am also having a problem with a new fuel gauge and sending unit from MidFifty. From my testing efforts, if your needle is pegged at full, the sending unit wire might being grounded out. To fully test, need to read the ohm readings coming from the sending unit.
My problem is that the gauge was always reading half. I got another new gauge and this one is always reading quarter tank (after I filled the tank). My sending unit was tested before going in and seemed to be ok. I'm still not sure what the problem is. I have an extra gauge and sending unit to hopefully figure it out. If I wanted a non-working gauge, I would have avoided all the time and expense and just left the original one in it!
My problem is that the gauge was always reading half. I got another new gauge and this one is always reading quarter tank (after I filled the tank). My sending unit was tested before going in and seemed to be ok. I'm still not sure what the problem is. I have an extra gauge and sending unit to hopefully figure it out. If I wanted a non-working gauge, I would have avoided all the time and expense and just left the original one in it!
Mountain Pass
Joined: Feb 2003
Posts: 236
Likes: 10
I am also having a problem with a new fuel gauge and sending unit from MidFifty. From my testing efforts, if your needle is pegged at full, the sending unit wire might being grounded out. To fully test, need to read the ohm readings coming from the sending unit.
My problem is that the gauge was always reading half. I got another new gauge and this one is always reading quarter tank (after I filled the tank). My sending unit was tested before going in and seemed to be ok. I'm still not sure what the problem is. I have an extra gauge and sending unit to hopefully figure it out. If I wanted a non-working gauge, I would have avoided all the time and expense and just left the original one in it!
My problem is that the gauge was always reading half. I got another new gauge and this one is always reading quarter tank (after I filled the tank). My sending unit was tested before going in and seemed to be ok. I'm still not sure what the problem is. I have an extra gauge and sending unit to hopefully figure it out. If I wanted a non-working gauge, I would have avoided all the time and expense and just left the original one in it!
So, I figured it just wasn't calibrated correctly. I bent the wire with the float on it way down, almost vertical. Now, if there's ANY fuel in there it lifts up. When I have 7 gallons in there now it reads about 1/10 of a tank, but at least now I can tell when I need to get gas.
I think these things just aren't made correctly, as many others have had similar problems. I do know it matters if you're running 6 volt (I am) or 12 volt.
Mountain Pass
Joined: Feb 2003
Posts: 236
Likes: 10
If you're running a 6 volt sender with 12 volt it probably won't work.... and vice versa. Voltage is related to current (I) and resistance (R) via V = I*R. I don't know what the gauge is actually reading, but based on the equation the resistance OR the current would have to be 2x the value for a 12V system vs 6V system and therefore the gauge would not read correctly (if at all) if mismatching 6/12 sender.
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Senior User
Joined: Mar 2017
Posts: 422
Likes: 28
From: Albany NY
Both the sender and gauge were supposed to be 12V. Is there any way to tell on the reproduction gauge if it is 12V or 6V?
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Freshman User
Joined: Nov 2016
Posts: 26
Likes: 0
Hi
I recently had exactly the same issue. A brand new fuel sender, the original (6v) gauge and I have converted the electrics to 12v. If you bought the voltage reducers that are for sale on macs/lmc then you have to create little adapter wires as the reducer needs to wire the wrong way round. I'll try and dig out some pictures of the back of my dash if it would help you but the stud on the reducer needs to go to the stud on the gauge and then you have two female connections between the sender wire and the reducer.
I think the senders aren't specific for 12v or 6v systems but you need to ensure the gauge only sees a maximum 6v and, as the sender comes after the gauge (at least in my system) the sender also just sees 6v.
Hope this helps? Let me know if it's a bit messy as I've written it in a bit of a rush
I recently had exactly the same issue. A brand new fuel sender, the original (6v) gauge and I have converted the electrics to 12v. If you bought the voltage reducers that are for sale on macs/lmc then you have to create little adapter wires as the reducer needs to wire the wrong way round. I'll try and dig out some pictures of the back of my dash if it would help you but the stud on the reducer needs to go to the stud on the gauge and then you have two female connections between the sender wire and the reducer.
I think the senders aren't specific for 12v or 6v systems but you need to ensure the gauge only sees a maximum 6v and, as the sender comes after the gauge (at least in my system) the sender also just sees 6v.
Hope this helps? Let me know if it's a bit messy as I've written it in a bit of a rush
Fleet Owner
Joined: Jul 2004
Posts: 27,287
Likes: 1,052
From: NM
...
I recently had exactly the same issue. A brand new fuel sender, the original (6v) gauge and I have converted the electrics to 12v. If you bought the voltage reducers that are for sale on macs/lmc then you have to create little adapter wires as the reducer needs to wire the wrong way round. ...
I recently had exactly the same issue. A brand new fuel sender, the original (6v) gauge and I have converted the electrics to 12v. If you bought the voltage reducers that are for sale on macs/lmc then you have to create little adapter wires as the reducer needs to wire the wrong way round. ...
Freshman User
Joined: Nov 2016
Posts: 26
Likes: 0
I was told a few times that you needed a reducer per gauge. As the metal strips connect all the gauges together, the only place I could put the 3 reducers was on the sender side of the gauge, which means a bit of difficulty in the wiring. Of course I could be completely wrong but it seems to be working
Senior User
Joined: Mar 2017
Posts: 422
Likes: 28
From: Albany NY
I decided to do a bench test with just the gauge, the sending unit and a battery. Hooked it all up and the gauge reads "full" until the sending unit lever is pushed all the way down (empty) and the gauge reads around "3/4". Since the bench test isn't working correctly, I'm think I should try a reducer.
What type of reducer are people using for the fuel gauge?
What type of reducer are people using for the fuel gauge?
Fleet Owner
Joined: Jul 2004
Posts: 27,287
Likes: 1,052
From: NM
I was told a few times that you needed a reducer per gauge. As the metal strips connect all the gauges together, the only place I could put the 3 reducers was on the sender side of the gauge, which means a bit of difficulty in the wiring. Of course I could be completely wrong but it seems to be working
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