Gas gauge not working. 1966 Barracuda

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kewen300

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1966 Barracuda, I loaded the car up on my trailer to bring it home. The fuel gauge worked when I loaded it up. I unload at my home the needle pegs to the full then fell right out past E. The temp sensor guage is working as normal. I picked up a new fuel sending unit as im going to put a new tank in this winter. I plugged the new sending unit in and grounded the fuel tube to the body. I still have no movement on the needle.

Could this be a circuit board issue?
Could this be the wire that goes from the sending unit to the dash?
Is there a glass fuse that power goes through first?

Looking for next steps.
Thank you
 
Sounds bad, because "I think" a 66 is like the earlier models, IE the gauge regulator/ limiter is inside the fuel gauge. Look and see if it has 3 terminals. It takes 12V at one terminal, regulates for the gauges, internally feeds the fuel gauge, and then sends regulated voltage out to the other gauges on a second terminal. The third terminal goes to the sender.

If the IVR is built into the fuel gauge (3 terminals) and they work, then the gauge may be toast.
 
The pattern you say is likely the fuel gauge got hit with full voltage and is burnt out. Especially that the needle is hanging far left of E.

That the temp guage is ok says the engine was cold when this happened and there was enough resistance in the sender to prevent it from being damaged. Personally I would disable the ivr. if it is in the fuel gauge it needs to be disabled as well.

I had my ivr fail closed 12v to the gauges. Mt fuel sender survived because the tank was almost empty. The engine was up to temp so there was enough current flow to over heat the gauge and it sat well below L and only got up to below normal when the engine was up to temp.

My gut says a cluster pull is in your future.

A last possibility is the sender wire shorted, that would cause similar symptoms and results
 
kewen300 said:
1966 Barracuda, I loaded the car up on my trailer to bring it home. The fuel gauge worked when I loaded it up. I unload at my home the needle pegs to the full then fell right out past E. The temp sensor guage is working as normal. I picked up a new fuel sending unit as im going to put a new tank in this winter. I plugged the new sending unit in and grounded the fuel tube to the body. I still have no movement on the needle.
Click to expand...
I may be assuming a few things here, but it sounds to me like the sender wire got pinched when you strapped her down to the trailer.
That would cause the needle to peg to full, with the wire finally giving up and the reading dropped to E. This would also cause the new sender to not register when you plugged it in and grounded it to the body (you DID move the float to confirm that it wasn't just resting on "E", right?). Simple to check, just check the wire from dash to rear (unhooked) with a continuity tester or ohmmeter.
By the way, use your original sender if at all possible. New replacements are known to be very inaccurate. Do a "search" of that topic on this forum, it's been pretty well documented.
 
You can check the gages and the senders for major faults with no power on using the resistance setting on a multimeter.
Also you can check the wires for major faults, like grounding.
That' s where I would begin a diagnoses.
You can do a visual check of connections and conditions at the same time. Wiring diagram in the service manual will show where the connectons are made and the color and gage of the wires.
The Master Tech Service Conference has a good explanation of how the gages work.

Side note: The ammeter [labelled alternator on the gage] works completely differently, and is wired seperately. It shows when the battery is discharging (running stuff) or getting recharged. Both of its wires are hot at all times.
 
Start by taking off the sender wire and grounding it. Turn the ignition to the ON position and see if the fuel gauge starts to come up from empty to full. If it does, don't let it peg all the way to the full side. If the needle moves like it should, the sender is the problem. If it doesn't move, the problem is from there all the way up and including the gauge. It's a good idea to change to a solid state IVR regardless. The IVR IS in the fuel gauge in a '66 Barracuda. If the fuel part of the gauge is toast, you're looking at getting a replacement or having your gauge rebuilt. Either way, do the IVR upgrade to keep it from happening again.
 
Dana67Dart said:
The pattern you say is likely the fuel gauge got hit with full voltage and is burnt out. Especially that the needle is hanging far left of E.

That the temp guage is ok says the engine was cold when this happened and there was enough resistance in the sender to prevent it from being damaged. Personally I would disable the ivr. if it is in the fuel gauge it needs to be disabled as well.

I had my ivr fail closed 12v to the gauges. Mt fuel sender survived because the tank was almost empty. The engine was up to temp so there was enough current flow to over heat the gauge and it sat well below L and only got up to below normal when the engine was up to temp.

My gut says a cluster pull is in your future.

A last possibility is the sender wire shorted, that would cause similar symptoms and results
Click to expand...
This is a photo of my gauges and I took the car down the road and warmed her up a bit. Don't worry temp evened out quick.

20250901_135205.jpg
 
Fuel gauge doesn't look to be in a bad place.

If it was touching the bottom of the E that would be bad
 

You need a 12v DC power source, ( battery or power supply)

Hook batt positive to the pin on the circuit board that is 12v in.

Then hook batt negative to the metal housing of the cluster.

Next you need a few resisters ( Amazon eBay etc.) 10 ohms, 5 watt or greater, 23 ohms, and 74 ohms. You can make 23 with 2 x 10 ohm and a 3 ohm in series. Don't get too hung up on the exact resistance values.

Wire one end of the resister/s to the same ground of the cluster housing.

And the other end to the pin that the sender would be attached to.

With 10 ohms the guage should read full scale, with 23 it should read 1/2 scale, and 73 it should read 0 scale ( C or E)
 
Is it possible to just hook up the sender instead of installing resistors?
 
67Dart273 said:
, I recently posted where I'd found some rheostats on ebay that would make good candidates for adjustable test resistors
Click to expand...
Only issue I have with rheostats is you have to turn them to a desired resistance then hook them into the sender cir WITHOUT moving the knob.

I tried that first and found a decade resistance setup to be much easier to use.
 
kewen300 said:
Is there a how to thread on converting the old IVR thats in the fuel guage to an external volt limiter? I've been trying to look.
Click to expand...
Go to the RTE site. Redfish is not so active anymore, he used to be the expert. He has a way of lifting the IVR ground so it is no longer active. Otherwise, carefully open up the gauge and "goop" the contacts open so they will not close

Basically, you have 12V switched from the key, into the fuel gauge to feed only the limiter. And the gauge is grounded, which is for the limiter. Then you have the output V of the limiter, internally feeding the fuel gauge, AND feeding it's output to a 2cnd stud, so that can jumper over to the other gauges. Last you have the sender stud, 3 in all

RTE Gauge Faq - rte

www.rt-eng.com www.rt-eng.com
 
As I've mentioned and posted before, I drilled a hole in the side of the fuel gauge instead of removing the face plate and having to find new rivets to re-install it. It's a matter of snipping one wire, and bending the points so they stay open. Otherwise, electricity will back up through those connections. Then a piece of tape over the drilled hole and you're done. Then it's finding a place to mount the new IVR and routing the wires. Fairly easy really.
 
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