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'78 Caballero... (Rally Gauges) Ok, I just put a brand new fuel sender in from OPGI. It is the correct level sender for my vehicle 22 Gal tank. I did some quick initial checks. I found 8.9-9 Volts and 30 Ohms resistance in the power wire going to the sending unit. To me, I'm assuming it should have 12V and I have high resistance cutting that to 9V causing the gauge to not read full. Does this sound correct? FYI... the gas gauge has never worked for me since I have owned the vehicle. I finally replaced the level sensor assy and this is now where I am at with it.

Thanks in advance!
 

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Can't wait for the answer to this...
Bought the same sender from OPGI for my 22 gallon tank and have exactly the same situation.

Arnie in Iowa
 

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the gauge has pos and neg supplied to it by the ign. the sender ONLY sends a ground signal to the gauge. you will get some residual voltage at the pink wire at the tank but it isnt suposed to supply the sender power.ground the pink wire at the tank ,it should make the gauge go to full.if it doesnt you need to check your dash grounds and the printed circuit contacts.if it does go to full the sender is bad or the rod needs adjustment
 

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Huh, i was going to say faulty guage, but i guess not? I will have 3/4 of atank for 2 weeks then a random morning it drops to 1/2. My guage sticks and i got a locking gas cap.
 

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the gauge has pos and neg supplied to it by the ign. the sender ONLY sends a ground signal to the gauge. you will get some residual voltage at the pink wire at the tank but it isnt suposed to supply the sender power.ground the pink wire at the tank ,it should make the gauge go to full.if it doesnt you need to check your dash grounds and the printed circuit contacts.if it does go to full the sender is bad or the rod needs adjustment
I will do this when I get home tonight. Now that you mention that it sounds familiar from trouble shooting the gauge years ago. Thanks!
 

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Unplug the pink wire - turn the key on the gauge should go past full. Ground the pink wire and it should go down past empty. If it does that you will need to pull the sendere back out and like ccc said adjust (bend) the rod that the float is on to get the right readings.
 

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Update... I finally got around to digging into this some more. Here's what I found; the gauge finally came off of 3/4 full and is now just whatever whenever. I know the sending unit it 90 ohms when full so I checked the ohms at the back of the fuel gauge and it was an un-godly amount of resistance something like 87K ohms. So I have a broken wire or corrosion or something somewhere. I got frustrated and gave up for awhile. I got back to it and decided to check from the lead from the tank. I got 22 ohms there so I know the sending unit is good!I then decide to probe the wire from the front progressively back to the tank to see where the excessive resistance drops off. Finally found the connection where the wires move from outside the cab to inside the cab. The connector wasn't secure as there is nothing to secure it. It just plugs in so after time it wiggled its way loose. Unplugged and plugged it back in and the gauge worked perfectly!! :nanawrench: Hope this helps anyone else with this same issue. Good luck!
 

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Update... I finally got around to digging into this some more. Here's what I found; the gauge finally came off of 3/4 full and is now just whatever whenever. I know the sending unit it 90 ohms when full so I checked the ohms at the back of the fuel gauge and it was an un-godly amount of resistance something like 87K ohms. So I have a broken wire or corrosion or something somewhere. I got frustrated and gave up for awhile. I got back to it and decided to check from the lead from the tank. I got 22 ohms there so I know the sending unit is good!I then decide to probe the wire from the front progressively back to the tank to see where the excessive resistance drops off. Finally found the connection where the wires move from outside the cab to inside the cab. The connector wasn't secure as there is nothing to secure it. It just plugs in so after time it wiggled its way loose. Unplugged and plugged it back in and the gauge worked perfectly!! :nanawrench: Hope this helps anyone else with this same issue. Good luck!

Your the first person in a year that I heard got it right. I've been waiting to change mine but nobody could find a fix.:beer:
CAN YOU TAKE A PICTURE WHERE IT PLUGS IN FOR EVERYONE TO SEE PLEASE.
Thanks
Robert
 
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