There’s nothing more frustrating than a fuel gauge you can’t trust. You’re watching the needle, wondering if you’ll make it to the next gas station, and the anxiety starts to creep in. Before you start buying parts, it’s important to figure out where the problem actually is.
Is it the fuel sending unit in the tank, or is it the fuel gauge in your dash?
At Tri-Starr Radiator in North Pitcher, NY, we’ve been helping Harley riders solve this exact puzzle for over 28 years. We’re a family shop, run by me, Dan, and my wife, Samantha, and we believe in giving you the knowledge to understand your bike. Let’s walk through how you can tell where the problem is.
The Quickest Test: The Dash Gauge Test
First, let’s check the gauge itself. This is a simple test that can save you a lot of time.
- Turn your ignition key to the “ON” position. Do not start the bike.
- Look at your fuel gauge. Does the needle move?
- If it moves to a specific position (even if it’s wrong), the gauge itself is probably getting power and is functional. The issue is likely the signal it’s receiving, which points to the sending unit or its wiring.
- If it doesn’t move at all—it’s completely dead—then the problem could be the gauge, a fuse, or the wiring to the dash.
This test points us in the right direction. If the gauge moves, we focus on the tank. If it’s dead, we look at the dash.
How to Test the Fuel Sending Unit
If your gauge moved during the test, the next step is to check the sender. The sending unit works on a simple principle of resistance, measured in ohms (Ω). You’ll need a multimeter for this, but don’t worry, it’s easier than it sounds.
Note: Always ensure the area is well-ventilated and there are no open flames or sparks when working near the fuel tank.
- Locate the Sending Unit: You’ll find it mounted on the bottom of your fuel tank. You’ll see the fuel lines and an electrical connector plugged into it.
- Disconnect the Electrical Connector: Carefully unplug the wiring harness that connects to the sending unit.
- Set Your Multimeter: Turn your multimeter to the resistance (Ohms Ω) setting.
- Test the Sender: Touch one multimeter probe to the center terminal pin on the sender and the other probe to the outer metal base or the second terminal (if present).
- With an empty tank: You should get a reading around 0-5Ω.
- With a full tank: You should get a reading around 88-100Ω (or up to 180Ω on some models).
- Check for Consistency: Slowly move the float arm up and down by hand. The resistance should change smoothly and steadily. If the reading jumps around, disappears, or doesn’t change at all, your sending unit is faulty.
What the results mean:
- A smooth change in resistance means your sender is likely good, and the problem might be in the wiring between the tank and the gauge, or the gauge itself.
- A reading that jumps to infinity (OL) or zero, or is erratic confirms the sending unit is bad and needs to be rebuilt or replaced.
When You’ve Determined It’s the Sender
You’ve done the tests and everything points to the sending unit in the tank. Now what? This is where we come in.
For over 28 years, we’ve made it our mission to offer quality fuel-sending units at an affordable price. We know how hard it can be to find these parts, especially for older models that the big manufacturers have discontinued.
- We Build New Units: For many Harley models, we manufacture brand-new, reliable sending units right here in our Upstate NY shop.
- We Rebuild Anything: If your unit is obsolete or you just want a more affordable option, our expert rebuild service can fix it. There are very few units ever made that we can’t repair, no matter how rusty or damaged.
- We’re Here to Help: Still not sure? That’s why we’re here. Just give us a call at (607) 486-4001. We can talk you through it, help you find your part number, and get you the right solution without the guesswork.
Don’t waste money replacing the wrong part. A few simple tests can pinpoint the problem, and we’re here to help you fix it for good.
