When I have a full tank it reads full but goes to empty when there is more than 1/2 tank. Did the ground test to the guage and needle goes to full. Then did the ground to the sending unit and also goes to full. The sending unit is a repro by 'Vintique Inc.'. Any ideas?
Thanks

 

I should read before hitting 'post' !

 

I test fuel senders on boats on a monthly basis, different ohms but they work the same. This is how I test them, works on any voltage or ohms. With key on ground the sender wire at the sender. You have done this and gauge reads full. This tells me the gauge and wiring are good and your system uses a low ohms (close to short to ground) to read full. I now remove the sender from the tank and connect the sender wire to it's terminal. Hook a ground wire to the sender mounting plate, this may be a wire already there or a jumper from the sender to any good ground. Slowly move the sender arm from full to empty, gauge should follow. If gauge moves down slowly then suddenly drops to empty you have an open in the sender (broken resistor wire or damaged wiper that loses contact with the resistor wire). If the gauge moves smoothly from full to empty but you only have the sender arm at 1/2 tank, or anything other than empty you have a mismatch between the ohms required by the gauge and that supplied by the sender.

 

I had a similar issue recently with a sending unit I purchased on ebay. Though the vendor swore it would work with my stock gauges it had to have been an incorrect model for my truck. The float read empty with 1/2 a tank of gas, it would have never reached the bottom of the tank to give me a correct reading as the float arm was too short. Don't know if your sending unit is new to you or not but another possible detail for you to check. I agree with the previous post by Rimrock. Do some manual testing of the float arm with the unit out of the tank and see how the gauge reads when moving it arm up and down. If you do some web searching you will find that the resistance has to match between the sending unit and the gauge which is another typical issue.

 

The problem is your POS "Vintique" sending unit.......it is not compatible with stock Ford King-Seally gauges. I tried one too....wouldn't work on ANY gauge, complete trash. I put a stock sender in works perfect.
The stock gauge does not use the typical ohm resistance system, so mixing and matching gauges and senders don't work.

 

what are the ohm values on the older senders? still the 10-73 ohm specs?

 

Sometimes it can be just a simple matter of bending the float arm correctly. I had a similar problem on my 48 F-3. What I did was fill the tank 1/2 full and then pulled the sender out and bent the float arm until the gauge read 1/2 full when it was back in. Then I drained the tank and it read empty just as it should...

 

Thanks for all the feedback. Mike, I will do your test today. Osubuki, I too bought a sender some time ago from Mac's and it also had a very short float arm. Scott, you are probably correct in your "POS" assesment. Where do I find a stock sender?
Thanks, Brian