Greetings all. First off, thanks to SSD and all the other board members who helped me sort out my "mystery vent" and carb issue earlier. The Golden Girl is back on the road and running great. Now to the next issue: fuel gauge isn't working. I've search this forum for fuel gauge issues and there are about 3 billion posts/recommendations/answers, so I'm going to throw this one out here and let the cards fall where they may.

71' Dart, 225, auto trans. Bought it for my Son as an XMAS present. Fuel gauge works a little, temp and amp gauges are operative (but the latter surges...a lot...but that's the next issue on the list). Back to the fuel gauge. With the key off, gauge is below empty, as it should be. When key is energized, needle rises to the first mark and stops. I crawled under the car and took off the metal ground strap on the metal fuel line at the tank and cleaned both up and reinstalled but it was no help. Next I took a circuit light and probed the lead going to the sending unit with the key on and got a constant flashing light there which indicates good power to the sending unit. I clipped the lead back on the sending unit and grounded it to the chassis which made the gauge climb, albeit slowly, to between 3/4 and full mark and stop ( car had less that 1/8 tank of fuel). I have an ohm meter but it doesn't go below 100 so I can't properly test the sending unit, but given the grounding power and the chassis ground test, would it be safe to say that the sending unit is bad? Thoughts?

The float for the sender unit probably has a pin hole leak. Replacements are available on Ebay.

So I bought a new sending unit, but before going to the trouble of removing the old one, I decided to test the new one. I took off the wire plug from the old unit and plugged it into the new unit and the grounded the new unit to the chassis. I got NO reading moving the float arm either direction by hand. I then used my test light and grounded the new unit at the power plug and the gauge moved to the 3/4 full mark just like the old sending unit does. So both old and new units act exactly the same. Any suggestions or ideas will be much appreciated. Getting a bit frustrated here

The gauge unit is a thermal unit that has a heating wire; the current through the heating wire varies with the sender resistance, which in turns varies with the float level. The thermal action of the gauge explains the slow nature.

The pulsed voltage on the fuel and temp gauge systems comes from a voltage limiter (regulator) in the dash unit. The issue ca either be the gauge or the limiter; it is unlikley to have 2 senders that are off and in the same way but you won't know 'til you test with an ohmeter. Borrow one and look for around 10 ohms full, around 23 ohms at half and around 73 ohms empty.

Testing the limiter is not strightforward; it is a form of power regulator actually, and no one has the thermal movement type of voltmeters anymore to test them. The best you can do is get a 6v flashlight battery and hook it to the output of the fuel gauge wire to ground and look to see if the lamp flashes at about a 1 flash per second rate and that the flashes are very brief; duty cyle is around 15-20%. You can also see if you temp gauge reads accurately but that is also subject to the quality of the cooling system action.

Gauge testing is ususally done by 1) just substituting another one or 2) setting upa test circuit. If you know someone with a variable power supply, you can set it to 5 volts and then hook up the gauge at the output with a 24 ohm resistor in series to see if the gauge reads half scale.

And if all this seems like a lot of rigamarole, the old factory manual test procedures employed test boxes with different settings to do just waht is described.

It's fixed! I did the RTE regulator upgrade and pulled/replaced the fuel sending unit. ALL the gauges work like a dream now (a shout our to RTE!!)and accurate as well. One word of caution. If you do the RTE upgrade and are trying to get the cluster past the steering column and it wont clear it, you may have to drop the steering column down a bit. There are 3 bolts (at least on my 71 Dart) that hold the column to the firewall. Etch around these and loosen ONE AT A TIME starting with the upper bolt. DO NOT REMOVE THEM ALL! You will eventually get the room you need to get the cluster out. When tightening the column back into place make sure to line up the marks you etched around the bolts you loosened. If you don't, the column will bind the steering and you will notice it considerably when you get for a test drive. Thanks again to all the helped!

Any 67-76 A-body requires the column to be dropped if you need ease of extraction and room to work...don't forget that if your car is 100% complete you have to pull the column bezel at the base of the dash (4 phillips screws), pull the 3 bolts at the base of the column at the fire wall, then with a deep socket loosen the 2 nuts and cupped grommet washers holding the column bracket to the base of the dash (3 if it's a pre-74- there is one farther back on the pedal bracket mount).... that will allow the steering wheel to rest on the seat and lots of room to work on the dash....

Reverse procedure is push the column up and install the cupped grommet washers and nuts and tighten, this should align the plate at the bottom of the column to install the 3 bolts, reinstall the bezel under the column at the dash...in the 1974-1976 cars the base of the column and plate changed a bit but the procedure is still the same.

If so will any new one work? Or has to be a certain type.
80 d150 SL6