Thanks to a board member here that located a rebuildable core I now have a rebuilt and hand calibrated '69 low fuel sender. This is the correct sender for 1969 Cougar XR-7 and Eliminator.
If you have a '67 or '68 XR-7 and want to upgrade to the 20 gallon tank, this is the sender you need, but you will also need the pig tail as the pin out doesn’t match your car. (I have a pig tail as well).
This sender includes a new thermistor, improved design brass float, filter, seal ring and Priority Mail in the USA. $259.99
Yeah… my sender decided I didn’t really need to know how much fuel I have. Might just be a leaky float, but not sure the low fuel light ever worked after I paid for a rebuilt unit from another source. Now… about that $200 for my core…
The only core I know of that is bringing that kind of money is the '71 Cobra Jet low fuel sender. The typical rebuildable low fuel core is worth $50 and a prepaid shipping label. My recommendation is that you have the core rebuilt and then sell it yourself. Keep in mind that many cores require a donor core to rebuild. Standard senders are worth about $20 and they are the source of donor parts in many cases.
Finally got around to replacing the sender. My old one did have a leaky float. Disappointing since I used a new brass float when I installed it.
When should the low fuel light come on? I drove around trying to run low enough on fuel to see if it worked, but got nervous and refueled before it came on. I was well into the red zone on the gauge.
You might want to contact me for troubleshooting help. The relay needs to work and a high resistance connection in the harness can be a problem. Does the lamp come on during cranking?
The lamp comes on when cranking. What does ‘prove-out’ prove?
Highest priority was getting the gauge fixed. I can live without the low fuel warning, but the uncertainty of fuel level was an impediment to enjoying the car.
It only proves the bulb works, and there is power to the relay.
You have to get down to less than 4 gallons, typically less than 3 to get the thermistor above the fuel level. By '70 they had moved it a little lower to avoid having it come on “too soon” or too often. Braking or turning can both effect the average level of fuel.
If you bought a gauge tester you have a bonus feature you can use. I don’t publicize it because it gets folks confused but let’s give it a try.
First off disconnect the plug from the sender. There are two connections in the pigtail that are actually used. One is for fuel level the other for LOW FUEL light. Connect the black wire of the tester to ground. The locking ring on the sender is a good one to use. Then with the tester switch ed to power, connect the red lead to one of the two hot connections in the pigtail. With the key in the accessory position if you get a flashing light that means you are on the gauge connection. If it is bright and constant then you are on the low fuel connection. (note: if you have a modern instrument voltage regulator behind the cluster you may not see a flash but a dimmer continuous light when connected to the gauge wire.) If you are not getting power here that means you have a bad connection some where between the relay and the tank, if the prove out to show the bulb lights up is working.
Here is the confusing part. Now that you are connected to the LOW Fuel wire in the pig tail, when you put the tester switch in the FULL position the LOW FUEL light should light up. When you put the switch into the Empty position it should go out. That’s right the way the LOW FUEL light works is opposite of the gauge.
If you can empty the tank of gas then you can pull the sender, add a ground wire from the sender to the tank, and test that way. It should take 15 to 30 seconds for the lwo fuel light to come on with the sender out of the tank.
Nifty little tool, that gauge tester. Does it do any other unadvertised tricks?
Unfortunately, my low fuel wiring failed the test - no bright/constant light when tester set to power. No low fuel light when set to full. Fortunately, the regular gauge is working.
I checked again at the pigtail connector in the trunk. Same result, so my problem must be in the harness. I’m not tearing things apart to find a broken wire, so I’ll just keep gas in the tank and pretend the LF light works.
Cool! Next stop is the relay. It is a bit hidden so you might not want to do this right now but I an tell you how to jumper it to verify that it isn’t working. I will shoot a picture of the relay and edit it to show you where to jumper. There is a chance I can get the relay working again, but it may be dead at this point. ( should add, it could also be a bad wire to the sender or bad connection in the harness, but we need to get to the relay to verify that)
Guys are using it as a test light. Basically they are putting it in the power position and using the Blue LED to look for power. It does work for that and it has alligator clips on each end so you don’t need as many hands.
I was concerned that 12V might overcurrent the blue led since it was intended to measure the presence of the 5-6V IVR output. Glad to know it is ok for that. You done good on that handy little gadget!
