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Old 10-04-2019, 10:02 AM   #1
REDROCKER652002
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Gas Gauge or Sending unit

Greetings to all,

I am hoping to help get the next in a long line of issues settled on my son's truck. It is a 69 step side. The issue at hand right now is the gas gauge or sending unit. Just to backtrack, I have replaced all the wiring with a brand new setup. American Auto Wire I think is the company. The box is in the garage and it is too cold for me to walk out there. LOL. Anyway, I checked the wire that hooks up to the sending unit and I have power there. When I plug in that wire and plug in the harness to the back of the cluster the gas gauge does not move. The gauge cluster has a new circuit board, so I don't think that is the issue. I used a square batter, 9 volt I think, out of my meter and clipped a the positive and negatives with a wire. Ran those wires to the posts on the gas gauge and the needle moves left and right depending on what I posts I have the wires clipped to, if that makes sense. So, my thought is the sending unit is bad. Am I on the right track? I searched the forum, and somebody posted that if I use my ohmmeter and touch the positive post and ground to the sending unit flange I should get some sort of reading. I am going to try that once it gets light enough to see. Any thoughts or suggestions would be most appreciated. Again, it is all new wiring and I have power to the wire that clips into the gas tank itself. So I am leaning towards the sender.

Thanks in advance for any help.

Dino AKA Dj's dad. LOL.
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Old 10-04-2019, 11:02 AM   #2
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Re: Gas Gauge or Sending unit

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Originally Posted by REDROCKER652002 View Post
Greetings to all,

I am hoping to help get the next in a long line of issues settled on my son's truck. It is a 69 step side. The issue at hand right now is the gas gauge or sending unit. Just to backtrack, I have replaced all the wiring with a brand new setup. American Auto Wire I think is the company. The box is in the garage and it is too cold for me to walk out there. LOL. Anyway, I checked the wire that hooks up to the sending unit and I have power there. When I plug in that wire and plug in the harness to the back of the cluster the gas gauge does not move. The gauge cluster has a new circuit board, so I don't think that is the issue. I used a square batter, 9 volt I think, out of my meter and clipped a the positive and negatives with a wire. Ran those wires to the posts on the gas gauge and the needle moves left and right depending on what I posts I have the wires clipped to, if that makes sense. So, my thought is the sending unit is bad. Am I on the right track? I searched the forum, and somebody posted that if I use my ohmmeter and touch the positive post and ground to the sending unit flange I should get some sort of reading. I am going to try that once it gets light enough to see. Any thoughts or suggestions would be most appreciated. Again, it is all new wiring and I have power to the wire that clips into the gas tank itself. So I am leaning towards the sender.

Thanks in advance for any help.

Dino AKA Dj's dad. LOL.
First off, you should not have any power to the wire that goes to the sending unit, that is a ground wire. If you did hook a 12v wire to it you may have damaged the sender. If you disconnect the wire to the sender and use a multi-meter set on 20k ohms, from the post on the sender to the tank you should get a reading. The reading you get would depend on how much gas is in your tank.

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Old 10-04-2019, 11:07 AM   #3
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Re: Gas Gauge or Sending unit

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First off, you should not have any power to the wire that goes to the sending unit, that is a ground wire. If you did hook a 12v wire to it you may have damaged the sender. If you disconnect the wire to the sender and use a multi-meter set on 20k ohms, from the post on the sender to the tank you should get a reading. The reading you get would depend on how much gas is in your tank.

LockDoc
HMMM, Ok. Good info, thanks. I will look again, but it is a brown wire that goes into the tab on the sending unit. I will try and get a picture with my tablet. Thanks, I will give it a try in a bit.
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Old 10-04-2019, 12:26 PM   #4
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Re: Gas Gauge or Sending unit

Ok. I am not trying to be a smart ass. Just trying to understand. Here is the wire I'm talking about. It runs into the dash gauge cluster that plugs into the back of the dash.
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Old 10-04-2019, 12:27 PM   #5
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Re: Gas Gauge or Sending unit

I thought that was how the gauge got the signal from the sending unit. Am I off?
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Old 10-04-2019, 12:39 PM   #6
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Re: Gas Gauge or Sending unit

https://www.youtube.com/watch?v=5Lt6mHrvuow

https://www.youtube.com/watch?v=MZhbdl95yCI

Here is a couple of videos
Hope this helps.




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Old 10-04-2019, 01:16 PM   #7
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Re: Gas Gauge or Sending unit

There are lots of good threads on the Forum as well ( I need to review them as I have issues with mine. “The coldest winter I ever spent was the summer I spent in San Francisco.” Mark Twain. So true!
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Old 10-04-2019, 01:21 PM   #8
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Re: Gas Gauge or Sending unit

Awesome. Thanks. When plugged into the gas tank, the gauge does not move at all. I did a test with a 9 volt batter, hooking up the positive and the negative to the back of the gas gauge and it moved the needle. So, I am thinking the gauge is working and the sending unit is not. If the gauge were bad, wouldn't the needle not move when the small test battery is plugged in? I am just trying to diagnose the issue before I go and spend 25 to 30 bucks on a new sending unit.

I plan on putting the ohmmeter on the sending unit as stated above and see what happens as well, so more posts to come LOL.

Thanks for all the help guys. Trying to just get this thing going for my son while he saves up money to get a new tank that will mount in the bed.
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Old 10-04-2019, 01:22 PM   #9
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Re: Gas Gauge or Sending unit

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There are lots of good threads on the Forum as well ( I need to review them as I have issues with mine. “The coldest winter I ever spent was the summer I spent in San Francisco.” Mark Twain. So true!
LOL. No truer words spoken. LOL
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Old 10-04-2019, 01:38 PM   #10
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Re: Gas Gauge or Sending unit

OK, so I took the gauge out of the cluster and tried using my ohm meter. Please excuse the stupidity of my post. When I touch the two terminals on the back of the gas gauge they register on the meter, but work their way down to zero. Is that normal? I don't recall ever using the ohm meter on my tester, so I am not sure I am doing it right. Any assistance would be most appreciated. I am still leaning towards the sending unit though.

Last edited by REDROCKER652002; 10-04-2019 at 01:54 PM.
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Old 10-04-2019, 01:46 PM   #11
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Re: Gas Gauge or Sending unit

I would remove the sender from the tank and test it.
Hook the leads up then move the float up and down.
Name:  ohms.png
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Check the float for any holes that would also make the sender not read.







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Old 10-04-2019, 01:52 PM   #12
REDROCKER652002
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Re: Gas Gauge or Sending unit

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I would remove the sender from the tank and test it.
Hook the leads up then move the float up and down.
Attachment 1945860
Check the float for a holes that would also make the sender not read.







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Yup, that was going to be my next move. LOL. But I have to get the kid out of it to do that. Thanks to all who replied. I appreciate all the input, as this is my first car that I have had to deal with wiring issues.
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Old 10-04-2019, 02:19 PM   #13
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Re: Gas Gauge or Sending unit

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Originally Posted by REDROCKER652002 View Post
Ok. I am not trying to be a smart ass. Just trying to understand. Here is the wire I'm talking about. It runs into the dash gauge cluster that plugs into the back of the dash.

I don't know how the AAW loom is wired but the wire from the sending unit plugs into the fuse block on the original wiring. If you look at the picture you can see the FUEL GA terminal on the right side of the fuse block. The original wire is tan.

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Old 10-04-2019, 04:11 PM   #14
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Re: Gas Gauge or Sending unit

This link may help.

http://67-72chevytrucks.com/vboard/s...d.php?t=640615
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Old 10-04-2019, 08:31 PM   #15
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Re: Gas Gauge or Sending unit

I didn't see any ground wire at the tank sending unit. It has to be grounded. If you had 12v at the sender wire (tan ) you probably don't have any ground.
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Old 10-05-2019, 11:31 AM   #16
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Re: Gas Gauge or Sending unit

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I didn't see any ground wire at the tank sending unit. It has to be grounded. If you had 12v at the sender wire (tan ) you probably don't have any ground.
I was just thinking the same thing. Might try and just run a ground wire off oe of the mounting bolts and go from there.

I am gonna fool with it today and see what I can come up with. Thanks.
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Old 10-05-2019, 11:39 AM   #17
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Re: Gas Gauge or Sending unit

I hate to appear stupid, but what the hell. LOL. I put the tester on the posts on the back of the gauge. They read, but then run down to zero. Is this supposed to be? Am I screwing something up.
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Old 10-06-2019, 12:37 PM   #18
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Re: Gas Gauge or Sending unit

Update to at least part of the issue. I lowered the setting on my meter to 20k. When I touched the probes to the left and right posts on the gauge I got a .04 reading. Then I touched the left to the bottom post and the right to the bottom post on the gauge and got .10 each time. Could it be that the meter was just set too high to get a reading? I am going to pull the sender later on in the week, when I am off work and check that the way you all have told me, but I am happy to at least get a reading on the meter. LOL.

Thanks to all who helped. RR
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Old 10-06-2019, 03:33 PM   #19
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Re: Gas Gauge or Sending unit

Maybe check the brass float on the end of the sending unit arm for leaks. If it's really old or even fairly new the solder joint could be compromised. You can shake it around when u remove the sending unit from the tank and if you hear sloshing inside then you know its trash. And based on my own personal experiences, you might consider switching to a plastic float. They practically last forever and no solder joint to worry about. I actually just bought one yesterday for my dads 64 c10. $4 on summit. $10 to ship. if your interested I'll post the part number.
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Old 10-07-2019, 02:02 AM   #20
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Re: Gas Gauge or Sending unit

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Maybe check the brass float on the end of the sending unit arm for leaks. If it's really old or even fairly new the solder joint could be compromised. You can shake it around when u remove the sending unit from the tank and if you hear sloshing inside then you know its trash. And based on my own personal experiences, you might consider switching to a plastic float. They practically last forever and no solder joint to worry about. I actually just bought one yesterday for my dads 64 c10. $4 on summit. $10 to ship. if your interested I'll post the part number.
That is my next step. Get the sending unit out and take a look at it. I still think that is the issue, but who knows. LOL

Thanks to all who posted replies, I really appreciate the info. My son would love to use the stock gauges, so this is a good start.

RR
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Old 10-11-2019, 03:13 PM   #21
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Re: Gas Gauge or Sending unit

Well, the problem has been solved. I took out the sending unit,and low and behold it works. A simple inspection of the float finds it to be cracked and worn. So, now off to find a new float. Problem is, it is a 5.00 part and 10.00 shipping LOL. Must be some other way to do this, right? Any help here would be much appreciated, but it is nice to know the gauge and the wiring seem to be working out just fine. RR

Last edited by LockDoc; 10-11-2019 at 07:29 PM. Reason: Remove WTB
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Old 10-11-2019, 07:28 PM   #22
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Re: Gas Gauge or Sending unit

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Originally Posted by REDROCKER652002 View Post
Well, the problem has been solved. I took out the sending unit,and low and behold it works. A simple inspection of the float finds it to be cracked and worn. So, now off to find a new float. Problem is, it is a 5.00 part and 10.00 shipping LOL. Must be some other way to do this, right? Any help here would be much appreciated, but it is nice to know the gauge and the wiring seem to be working out just fine. RR
I edited your post above and removed the WTB sentence. You need to be a Premium member to post a "Want To Buy". If you click on the word "Subscribe" in the menu bar at the top of this page it will explain the different subscription options.

Thanks,
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Old 10-11-2019, 11:09 PM   #23
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Re: Gas Gauge or Sending unit

Amazon is where I buy them. Free shipping baby.

https://www.amazon.com/Omix-Ada-1772.../dp/B003AOM17I
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Old 10-13-2019, 02:39 PM   #24
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Re: Gas Gauge or Sending unit

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I edited your post above and removed the WTB sentence. You need to be a Premium member to post a "Want To Buy". If you click on the word "Subscribe" in the menu bar at the top of this page it will explain the different subscription options.

Thanks,
LockDoc

OK, sorry, I thought if that was just if I was trying to sell something. I figured if somebody had one laying around and wanted to get rid of it, I would rather give the money to a board member. Won't happen again, I promise.
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Old 10-13-2019, 02:41 PM   #25
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Re: Gas Gauge or Sending unit

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Amazon is where I buy them. Free shipping baby.

https://www.amazon.com/Omix-Ada-1772.../dp/B003AOM17I
Awesome!!!!! Thank you so much for the info, that one is cheaper than the other when you include shipping and my wife has a prime account. I don't want to buy a whole new unit as my son will be relocating the tank to an underbed one once he gets enough money saved.

thank you so much for the link. I appreciate it

RR
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