Gas gauge not working.

[Street fighter]

I have a 73 charger that is in need of the gas gauge repaired or replace. I have replaced the tank sending unit twice so I don't think it's the sender. the hand was going to full if you added 5 gallons to the tank. Now the hand sits in the empty location and jumps back and forward. I don't know much about the gauges, but I have made sure that the sending unit is well grounded and there is voltage going to the sending unit. I'm thinking about sending the dash gauge section to have it tested and repaired if they need it,I only use the gas gauge because I have aftermarket water, oil,and voltage gauges. have anyone had this happen and if so how did you fix it?

 

[rick68b5]

Ground the gas gauge wire if it goes to full it's a ground problem on the sender

 

[Street fighter]

Ground the gas gauge wire if it goes to full it's a ground problem on the sender

We are talking about the hot wire right?

 

[rick68b5]

Yes

 

[Street fighter]

Yes

Yes

Thanks, hope that's all it is.

 

[HALIFAXHOPS]

Could be the current limiter also, the other gauges work?

 

[bschomske]

Buy a new gauge.thats what i ended up doing.90 dollars from year one for a 1969 runner guage...

 

[oldbee]

My best informed guess is g— d—— Chinese junk sender. Mine doesn’t go over 1/2 full, shoulda cleaned&re used the original.

 

[Street fighter]

Could be the current limiter also, the other gauges work?

All of the other gauges have been replaced with manual gauges, checked the oil gauge by grounding the hot wire but nothing no movement.The gas gauge just sits there jumping back and forward on empty.when checking it to make sure it was grounded it did move very, very slowly beyond the empty mark that took about a minute and stopped. the tank should have a lot more than that.

 

[bherman]

I have a 73 charger that is in need of the gas gauge repaired or replace. I have replaced the tank sending unit twice so I don't think it's the sender. the hand was going to full if you added 5 gallons to the tank. Now the hand sits in the empty location and jumps back and forward. I don't know much about the gauges, but I have made sure that the sending unit is well grounded and there is voltage going to the sending unit. I'm thinking about sending the dash gauge section to have it tested and repaired if they need it,I only use the gas gauge because I have aftermarket water, oil,and voltage gauges. have anyone had this happen and if so how did you fix it?

Street fighter, I recently went through this on my 66 Satellite and I have some thoughts for you. The voltage limiter on the cluster is really an antique 1970's version of a pulse width modulator. It's a set of points that has enough "off" time to create approximately a 5 volt average based on time. Ma Mopar added a capacitor to help smooth the voltage spikes and used a slow to warm-up (and react) coil in the gauge. This keeps the needle from jumping with the voltage fluctuations. If the voltage limiter is not cycling at the correct rate (too much off time) the average voltage that it produces will be low and cause a larger lag in the gauge movement. The aftermarket solid state voltage limiters (remove the capacitor) produce steady state voltage and the gauge responds much quicker. If you can read the voltage to the sending unit connector you're reading through the voltage limiter and gauge circuit. It's difficult to get an actual voltage at the connector because it's not stable with the original style limiter. If you have voltage at the sending unit connector, bypass the sending unit, ground the connector to a low resistance ground, wait 90 seconds for the gauge coil to warm-up and it should read full. If it doesn't read full a check of the voltage limiter and the gauge is indicated. (note if the circuit/wire running to the sending unit has significant resistance it can also cause this condition). The rheostat in the sending unit deceases the resistance to ground as the float rises, so unfortunately any unintended resistance will make the gauge read low. I tried two sending units and still only managed to achieve an almost full reading at the gauge when the tank is full. I hope that this helps, Brian

 

[Dennis H]

Ground. Join the club.

 

[Fran Blacker]

Turn key to on, don't start engine. Listen for a bink while watching gauge. If you hear that sound and gauge bounces voltage limiter.