I was trying to figure out why my fuel gauge doesnt work at all yesterday so I tried to see if iI was even connected or if it had a solid ground. I dont really know how to test this. There is one black wire going to the sending unit. I pulled it out and tried to use a volt meter by putting the red to the wire coming from the tank and grounding the black to the frame, turned the key and it didnt read anything. But all honesty, I dont know anything about how to check current so what did I do wrong, or what should I do to test to see if the sending unit is even getting any power?

 

The sending unit doesn't receive power, it just completes the circuit using a variable resistor to ground.

A quick test to see if the gauge itself is working is to pull the wire leading to the sending unit and ground it, then turn the key on for a few seconds to see if the gauge goes to F (make sure you only turn the key for a few seconds to avoid burning out the gauge)

If the gauge goes to F, then the problem is with the sending unit.

You can easily remove it for a proper test, just make sure you siphon out the fuel before removing the locking ring.

It's also a good idea to have a new gasket on hand in case you tear the old one.

Once you have the sending unit out, connect an ohm meter between the sender body and the output post.

Move the float arm back and forth and look for a change.

I believe the stock reading should be 10-70 ohms

 

It could also be not grounded good. That is where you use a band clamp to attach a wire to the curved part of the sending unit and then ground the other end of the wire to the frame.

 

Snake Eater- Thanks! yeah ill test this out tomorrow and see if the gauge moves at all!

Bremereric-Where is it grounded?? Also, ill put a picture of it up tomorrow, but what is the copper little loop on hose thats going to tank? and also, what is the little plate for? Theres a plate that shields it, im guessing to protect it from debris but idk.

 

First, WHAT ARE we workin on?

Your 74 RR? That's just a guess, who knows?

If you are working on a typical 12V Mopar musclecar, you have several issues that could be in play, from front to rear

First, the temp and fuel gauge are both supplied power by the instrument voltage limiter, a unit which (in most clusters) is a small rectangular unit that plugs into the rear of the cluster, and supplies reduced power to the two gauges, also the oil gauge if you have one.

The very first test, grounding the sending wire to see if the gauge moves, is only a basic test, but a very good start.

An indication that the voltage limiter is at least "somewhat working" is, does the temp gauge work OK? (We don't know, you may have installed a different gauge)

If the temp gauge functions but the fuel does not, at least you know the limiter is "mightbe" OK

The gauge nuts could be loose/ corroded on the rear of the cluster

The sender wire could have lost connection at the cluster harness connector, and the rear harness kick panel connector, or at the sender itself.

The sender could be bad, the sender might not be grounded. Originally, these had a clip which jumpered across the rubber fuel connector hose. You can use a small clamp on the sender fuel outlet, clamp a pigtail wire to that and attach the wire to a body ground.

 

Okay so today i finally pulled the tank because i though it would be full of crap but i found out it was spotless. Once i had it out i tested the fuel sending unit and made sure that it went from 10 to 60 when i moved the float from empty to full. Then i checked to see if my float actually floats and it does. So that work and I reassembled the tank. I then grounded the wire and turned the key to see if the gas gauge would move at all and it didnt. My temp and fuel gauges dont work so that leads me to believe its the limiter that you described. Is this an expensive thing to fix? what other tests should i look for??

 

Anyone? Can a voltage limiter be easily replaced?

 

It is a small metal unit. Plugs into the back of the Instrument circuit board. There also is a plug on the circuit board with pins for the plug- sometimes they come loose and loose connection. Need to be re soldered

 

Is it something that i could do with a normal soldering iron? I dont know much about dashes and stuff but i have the ability to solder a wire.

 

On some cars it's a small rectangular box that plugs into the rear of the cluster. On some Rally clusters it's built into the fuel gauge. I would buy a solid state replacement from someone like RTE engineering. Google it

https://www.google.com/search?newwin...tage%20limiter