Gas Gauge Sending Unit Not Registering Below 1/2 Mark

[47heaven]

Was testing the one-wire aftermarket gas gauge sending unit today to see if it was registering with the gas gauge which I replaced with an aftermarket one to replace the old two-wire assembly that I never had luck with. I connected the sending unit outside the tank, grounded it and moved the arm to the full position. Then, I turned on the ignition switch, and it registered full...which was a good sign. I went back to the trunk and moved the arm down slowly. The needle on the gauge followed accordingly, but when I got passed the 1/2 mark, the needle would drop to empty. When I moved it back up past the 1/2 mark it would register again as I would move the arm all the way to full. I repeated it numerous times, but the same thing would happen. If I moved the arm back and forth between 1/2 and empty, nothing would register on the gauge until I passed the 1/2 mark towards full. I checked to see if any of the wires behind the gauge were loose, but they were tight. Any ideas what could be causing this?

[Alshere59]

A two wire sender works differently than a single wire so they are not compatible. You have two options replace the sender with a two wire or replace the gauge. Not what you wanted to hear but...

 

This may help if you have the old sender.

http://mopar.pairserver.com/p15d24ph_forum/index.php?/topic/6155-how-to-test-a-fuel-sender-unit/

[Merle Coggins]

Do you have an Ohm meter to measure the resistance through the sender? It sounds like the sender has a dead spot under the 1/2 spot. Check the resistance of the sender between the terminal and ground (sender body) and watch the resistance change as you move the float.

 

Merle

[Don Coatney]

A bit of history on this problem would be very helpful in suggesting a soloution to this problem. Has this gauge ever worked? If it did what changed? Can you post links to all the other threads you have started and discussed this problem so we can get the full picture on what has already been suggested and tried? Without this history is is almost impossible to assist you.

[Alshere59]

Merle Don

I think he gave the problem in the first part of his original post. Unless you know of a way to get a two wire gas gauge to work with a single wire sending unit then he can't really help with anymore info. The two designs work completely different and cannot be replaced with parts from each other. If he has the old sender the thread I referenced can help him trouble shoot that. The link also says the same thing they are not compatible. If he did replace the gauge with a single wire unit as well (which I don't think he did) then he needs to look at the ohms ranges for each. If those are off it would show as he describes..

 

http://mopar.pairser...el-sender-unit/

 

Al

 

Was testing the one-wire aftermarket gas gauge sending unit today to see if it was registering with the gas gauge which I replaced with an aftermarket one to replace the old two-wire assembly that I never had luck with.

[47heaven]

Gentlemen...I believe I stated in the original post that the gauge and the sending units are both of a one wire system now. Don, there was no need to go back and reference what I posted in the past about what I had inquired regarding the sending unit because that was referring to the original two-wire system, which doesn't do me any good...whole different system to work with now. I was merely asking why the sudden drop after 1/2. I did forget to mention that as I moved the float arm, I noticed there was kind of a rough, lull feeling as it hit the 1/2 mark, but only at that mark. I could still hear brush moving along the sensors inside when I moved it towards empty. Also, this one-wire hook up worked when it was first installed with the original tank.

 

Once again, the gauge is a new one-wire unit with the original face on it. The sending unit is also a newer, one-wire unit, as well. Somewhere on here I may have posted when I fabricated that, but not sure. As Alshere said, I have given all the info I could on the issue. Just trying to understand what is going wrong. A buddy of mine will be stopping by with his Ohm meter to do some more testing.

 

Also, another question I have....if I hold the unit straight up and down, hold the float arm up then let go, should it move down by itself or is it supposed to have some give in it so that it has to be moved physically, like I have been having to do. It just feels like it may be too tight to move when the gasoline is being filled into the tank, and there is no way to adjust it. Just another thing I'm wondering about.

[Merle Coggins]

The arm should drop under its own weight, otherwise it wouldn't follow the level of the fluid as it goes down. It sounds like you have a defective sender.

And for the record, I understood your initial post as having a different gauge to match the sender. That's why I offered the advice of checking the resistance of the sender to verify if it is working properly or not. That's a standard test for a sender like that.

Merle

[Plymouthy Adams]

I was totally aware of his one wire aftermarket system installed..I also know that he lately changed the tank..is the new tank baffles in the way and preventing the float arm from working properly,..I think the new tanks are baffled whereas the stock originals were not...just some food for thought.,....

[Alshere59]

I stand corrected as definitely misread your post. You have my apology gentleman. With that said the advice was accurate as well. Wish you luck getting it dialed in.

[47heaven]

Tim, I had already checked and adjusted the sending unit's height so that the float touched the bottom of the tank just before it would have been at total empty position on the unit. Also, when I install it, it won't hit the baffle because the float arm will go to the right instead of the left, where the baffle is.

 

I was totally aware of his one wire aftermarket system installed..I also know that he lately changed the tank..is the new tank baffles in the way and preventing the float arm from working properly,..I think the new tanks are baffled whereas the stock originals were not...just some food for thought.,....

[47heaven]

The arm should drop under its own weight, otherwise it wouldn't follow the level of the fluid as it goes down. It sounds like you have a defective sender.

And for the record, I understood your initial post as having a different gauge to match the sender. That's why I offered the advice of checking the resistance of the sender to verify if it is working properly or not. That's a standard test for a sender like that.

Merle

Merle...yes, I saw your advice, and I will use that when my buddy comes by to help me test the voltage. I guess the initial beginning of that last post was meant for Don and Alshere59 because I think that they thought that I was reinstalling the old gauge and two wire system and was referring me to post links that had nothing to do with what I am working with.

Darin

 

Edited April 17, 2013 by 47heaven

[47heaven]

I stand corrected as definitely misread your post. You have my apology gentleman. With that said the advice was accurate as well. Wish you luck getting it dialed in.

No problem. I noticed that you had caught on to what I had originally said, but no biggie. I think we're on the same page now, and your advice sounds accurate to me.

[47heaven]

Tested the fuel sender unit yesterday, and of course it failed past the 1/2 position, as expected. Took the unit apart to see what what was hanging it up and clearly saw that some of the wire sensors had come apart and bent back. Anyway, will be purchasing a new unit this afternoon and install it. Will be good to finally close the book on this chapter.

[55 Fargo]

Darren, get another sender unit, that sure sounds like the trouble. This should a quick fix, hope all goes well. I just read the thread, and even before I got through, my guess is a dfective sending unit good luck.......