Inside the gauge, are wire coils which make up electro magnets, strategically placed to create competing magnetic fields around the base of the needle. The sender unit has a variable resistor inside, controlled by a float in the tank which changes resistance with fuel level. The sender unit is actually a part of the gauge circuit, requiring two connections. One connection is obvious (wire from sending unit to gauge) the other is, the body of sender and gauge must be connected to each other (grounded). The sender is wired into the gauge in a way that strengthens or weakens the magnetic field on one side of the needle, moving the needle toward E or F depending on float position. There should be a ground wire connected to the gauge mounting stud coming from the harness. The ground for the sender unit is actually the metal fuel line between the pump and the tank. The pump is connected to the frame with a wire. If you have added a nonconductive fuel filter or rubber line between the pump and the tank, you have broken the sender ground return path so you must add a wire from the sender body to the frame. (Figure 1)<\/p>\n
Using a multimeter set to measure ohms, check for zero ohms between chassis\/frame and sender unit body. If not zero ohms, attach an 18ga wire sender unit mounting screw or cover plate screw, to chassis\/frame.<\/p>\n Next measure ohms between output terminal screw and sender unit body. This should measure between 0 and 90 ohms. A near empty tank will read less than 20 ohms and a nearly full tank will read greater than 60 ohms. If all measurements are good, the sender is good. You can also remove the four screws and cover from the fuel sender and carefully move the metal fingers connected to the float arm, up and down to measure the full range of the output. Note: The pivot arm does not have a seal so you might have a small amount of fuel inside the unit that has wept passed the pivot. Have a rag or a catch can ready to catch it.<\/p>\n Gauge testing <\/strong><\/p>\n Check for zero ohms between gauge mounting stud and chassis\/frame. If not zero ohms, attach an 18ga wire from gauge mounting stud to frame.<\/p>\n Check for 12v on gauge terminal screw B with key on. I built a \u201cGauge Tester\u201d (mimics the fuel sender) that can be used in the car or on the bench using a 100 ohm potentiometer, small ABS box and two test leads. If in the car, remove the wire from terminal T or fuel sender and attach one wire from the test box. Attach the other wire from the box to ground. Turn the knob on the box and watch the needle move.<\/p>\n On the bench you will need a 12v power source connected to the gauge. Gauge Range Tester <\/strong><\/p>\n Materials Bob Shafto – May 8, 2024 \u201cFuel gauge not working\u201d is a topic that comes<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[14],"tags":[],"class_list":["post-50516","post","type-post","status-publish","format-standard","hentry","category-featured-tech-sessions"],"_links":{"self":[{"href":"https:\/\/namgar.com\/NAMGARMAIN\/wp-json\/wp\/v2\/posts\/50516","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/namgar.com\/NAMGARMAIN\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/namgar.com\/NAMGARMAIN\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/namgar.com\/NAMGARMAIN\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/namgar.com\/NAMGARMAIN\/wp-json\/wp\/v2\/comments?post=50516"}],"version-history":[{"count":0,"href":"https:\/\/namgar.com\/NAMGARMAIN\/wp-json\/wp\/v2\/posts\/50516\/revisions"}],"wp:attachment":[{"href":"https:\/\/namgar.com\/NAMGARMAIN\/wp-json\/wp\/v2\/media?parent=50516"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namgar.com\/NAMGARMAIN\/wp-json\/wp\/v2\/categories?post=50516"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namgar.com\/NAMGARMAIN\/wp-json\/wp\/v2\/tags?post=50516"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/namgar.com\/NAMGAR2020\/wp-content\/uploads\/2025\/01\/1.jpg\")
In vehicle testing <\/strong><\/p>\n
\nCheck that gauge terminal screw to frame resistance. is the same as sender terminal screw to frame.
\nCheck resistance terminal B to terminal T = 61 ohms +\/- 10%
\n\uf0b7 If resistance between B and T = 154 ohms, B coil is open
\n\uf0b7 If resistance between B and T = 99 ohms, Bar coil is open
\nCheck resistance terminal B to case = 160 ohms +\/- 10%
\nCheck resistance terminal T to case = 99 ohms +\/- 10%
\nIf the B terminal is open, the gauge reads empty.
\nIf the T terminal is open, the gauge reads full.
\nIf ground is missing on the sender, the gauge reads full
\nIf ground is missing on the gauge, the gauge reads empty<\/p>\n
\nNote: the original gauges will read full when the tank is \u00be full.<\/p>\n
\nPotentiometer – 100Ohm, Linear, Knurled, 5W, Wirewound, with knob.
\nABS Plastic Electronics Enclosure or Project Box 2.5×1.7×1.2 in O.D
\nWGGE WG-026 10 Pieces and 5 Colors Test Lead Set & Alligator Clips, 20.5 inches<\/p>\n![\"\"](\"https:\/\/namgar.com\/NAMGAR2020\/wp-content\/uploads\/2025\/01\/2.jpg\")
<\/p>\n![\"\"](\"https:\/\/namgar.com\/NAMGAR2020\/wp-content\/uploads\/2025\/01\/3.jpg\")
<\/p>\n","protected":false},"excerpt":{"rendered":"