Testing Fuel Gauge
- Thread starter Bob56
- Start date
corvette8n
Well-known member
I think you can use a 1-1/2 volt battery to see if the needle moves., if you have an aftermarket sender in the tank you’ll never get an accurate reading on your gauge.
glennpm
Well-known member
The electric fuel gauge has a coil that heats up with amperage from the tank sender which also has variable output controlled by arm position which heats a bi-metal strip sending amps to the gauge.
From https://forums.aaca.org/topic/238627-1936-ford-fuel-gauge-repair/
"19tom40 Posted June 30, 2014
A good original type sending unit should read near 0 ohms at all positions of the arm. An ohm meter will read the resistance of the coil wound around the bi-metal strip and the resistance of the contact points. The coil only has a few windings and will have very little resistance. The dash unit has no control over the amount that the needle moves, this is done by the sending unit. As the amount of fuel shown by the dash gauge is just an approximate value, the full current test is accurate in determining if the gauge is functional.
Here is a photo of the inside of an original type fuel sending unit. The gap in the contact points is controlled by the position of the float arm. If you do not have an original type available to you, remove the tank unit and connect it to the gauge with a jumper wire. Measure the depth of the tank and bend the arm on the sending unit to travel that distance. I like to have about 1.5" straight section near the part that moves the resister slider and then a 90 degree bend that is adjusted for the depth of the tank. Check to see that it reads full near the top and empty near the bottom. I don't have a photo of one at this time.
"
Koates may chip in here.
Glenn
From https://forums.aaca.org/topic/238627-1936-ford-fuel-gauge-repair/
"19tom40 Posted June 30, 2014
A good original type sending unit should read near 0 ohms at all positions of the arm. An ohm meter will read the resistance of the coil wound around the bi-metal strip and the resistance of the contact points. The coil only has a few windings and will have very little resistance. The dash unit has no control over the amount that the needle moves, this is done by the sending unit. As the amount of fuel shown by the dash gauge is just an approximate value, the full current test is accurate in determining if the gauge is functional.
Here is a photo of the inside of an original type fuel sending unit. The gap in the contact points is controlled by the position of the float arm. If you do not have an original type available to you, remove the tank unit and connect it to the gauge with a jumper wire. Measure the depth of the tank and bend the arm on the sending unit to travel that distance. I like to have about 1.5" straight section near the part that moves the resister slider and then a 90 degree bend that is adjusted for the depth of the tank. Check to see that it reads full near the top and empty near the bottom. I don't have a photo of one at this time.
"Koates may chip in here.
Glenn
Drbrown
Well-known member
If you get the system working but your dash gauge is working but inaccurate, there is a way to adjust the dash gauge to accurately show the tanks contents. It involves adding measured amounts of gas to the tank. Then dropping the dash gauge itself down "live" to access its interior and adjust it's settings. I've done all my dash gauges in that manner. I may have posted the instructions here long ago or you can PM me.
Skyking227
Junior Member
Dr Brown
Could you send me your testing instructions for gas gauge.
I set up test bench with nos gauge and a used float all King Sealy, I believe.
Using a 12 v battery, switch and single voltage reducer12 to 6v, checking voltage, gauge started smoking.gauge was at full swing.
Everything was grounded, can’t see my problem.
Regards
Skyking
Could you send me your testing instructions for gas gauge.
I set up test bench with nos gauge and a used float all King Sealy, I believe.
Using a 12 v battery, switch and single voltage reducer12 to 6v, checking voltage, gauge started smoking.gauge was at full swing.
Everything was grounded, can’t see my problem.
Regards
Skyking
glennpm
Well-known member
Please re-read the rest of the posts within this thread. Instructions have already been provided. Testing should be a quick intermittent application of voltage with a AA or AAA battery otherwise you may burn it out.
hueyhoolihan
Well-known member
FYI...
i discovered that the some of the dashboard gauge wiring on my '41 involved conductive plates. my research showed, and empirical evidence also showed, that wires with sufficient gauge to effectively dissipate heat (i.e. thick enough) and with the flexibility (thin enough) to do the job don't exist. in that if they are not thick enough heat will melt the insulation, and if not thin and flexible enough it's next to impossible to manipulate them into position. so much so that Ford decided that plates were necessary to do the job. in particular between the fuel gauge and the oil pressure gauge.
i discovered that the some of the dashboard gauge wiring on my '41 involved conductive plates. my research showed, and empirical evidence also showed, that wires with sufficient gauge to effectively dissipate heat (i.e. thick enough) and with the flexibility (thin enough) to do the job don't exist. in that if they are not thick enough heat will melt the insulation, and if not thin and flexible enough it's next to impossible to manipulate them into position. so much so that Ford decided that plates were necessary to do the job. in particular between the fuel gauge and the oil pressure gauge.
glennpm
Well-known member
There are good options now. I found out about multi (gazillion) strand wire for RC cars, etc. My 2007 Buell had a wiring design issue. A main ground termination, with a cold fused joint, was near the end of a run right through the headstock, an obvious fatigue from bending flaw. Someone in the group mentioned it. I bought some then and then a bunch later for an '87 XS650 project.
https://www.acerracing.com/collections/superworm-wire
For larger gauges, use welding cable which is also very flexible using multi strands and slippery inner casing.
ford38v8
Well-known member
Huey, I’m thinking this is foggy thinking…. Heat is related to resistance, so a heavier gauge wire having negligible resistance produces no heat.
deuce lover
Well-known member
What glennpm said in post #4. I have worked on these gauges for yrs and use a 9V smoke detector batt with alligator clips attached to wires .That hold them secure to the batt terminals.I just touch those wire momentarily to the gauge lugs.If needle moves the gauge is good - to me.I reverse polarity if no movement .If still no movement I open up the gauge and do surgery.Most times that heating element wire is severed.Sometimes I am able to do a repair and sometimes not.