wrong reading on fuel gauge
Freshman User
Joined: Jan 2004
Posts: 44
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Does your guage still move but it's just way off? Because thats what mine does and I would be interested to hear about any solutions also. I've just delt with it but I would like to fix it I just thought I would have to take the dash apart to get to the guages and fix'em and i'm lazy right now.
Post Fiend
Joined: Jun 2003
Posts: 8,209
Likes: 12
From: Black Hills of SD
Unplug the wire from the sending unit on the tank and see if it goes down. If it does then it is the sender, if not very liely it is the guage. I have owned a bunch of these old pickups and the guage is never accurate nor is it capable of being. I messed with my float vor several hours on a 68 and there was just no adjusting it to be accurate on both ends. As a matter of fact the amp and oil pressure guages are pretty much junk too. The oil pressure guages tend to read low and I am sure that the amp guage isn't even hooked up, I have yet to see one move.
New User
Joined: Jan 2008
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Not getting a proper voltage signal & having a bad ground on the circuit can also cause this problem.
Start by checking the voltage of the temp sending unit wire with the key on.
It should be a steady pulse of 5v measured with an analog (sweep) volt/ohm meter.
If you have those two, the chances are, willowbilly is correct the problem is the sending unit.
Start by checking the voltage of the temp sending unit wire with the key on.
It should be a steady pulse of 5v measured with an analog (sweep) volt/ohm meter.
If you have those two, the chances are, willowbilly is correct the problem is the sending unit.
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Junior User
Joined: Feb 2004
Posts: 73
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From: springfield,or
i checked voltage today and cleaned the ground as best i could i could'nt take out the plug that hold the screw in. i show a steady 12 volt reading with the key in the on position. More help please
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
If the instrument panel voltage regulator loses it's ground connection the gages are sent 12V instead of a pulsating voltage. The "regulator" is nothing more than a signal flasher that turns power on and off (on about 35% of the time). Clean the contacts under the regulator and see if it works, if not replace the unit. When you replace the unit use silicone dielectric grease on the mounting tab to protect the connection.
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Freshman User
Joined: Oct 2003
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The oil pressure guages tend to read low and I am sure that the amp guage isn't even hooked up, I have yet to see one move
Try running the battery way down, and then starting the truck, you should see the amp gauge move over to charge, or you can unhook the alternator and turn on lots of lights and fans, and then it will move to discharge. If that don't work, then it really is unhooked, but me being a car audio nut, I constantly run mine for hours at at time when working outside, and when I start it, the gauge always learns torward charge, slowly moving back to the middle as the battery charges.
Try running the battery way down, and then starting the truck, you should see the amp gauge move over to charge, or you can unhook the alternator and turn on lots of lights and fans, and then it will move to discharge. If that don't work, then it really is unhooked, but me being a car audio nut, I constantly run mine for hours at at time when working outside, and when I start it, the gauge always learns torward charge, slowly moving back to the middle as the battery charges.
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Post Fiend
Joined: Jun 2003
Posts: 8,209
Likes: 12
From: Black Hills of SD
Well maybe but under normal operating conditions don't expect to ever see the needle move on a Ford pickup amp guage. I have worked on a lot of Ford pickups and done full electrical diagnosis with a Snap-on AVR and a carbon pile load tester on dozens if not hundreds, and run the system full fielded and still never saw a twitch out of a Ford pickup ampmeter. I run a voltmeter in all mine. It tells you alot more like battery state, starter draw ect. If the volts are where they belong it really doesn't matter what the ampmeter reads.
Freshman User
Joined: Oct 2003
Posts: 37
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Yeah, I would have to agree with you that voltmeters make much more sense, but yeah, the ampmeter in mine never moves either unless I discharge the battery a ton before starting, or if the charging system is not working properly and you are drawing a heavy load off the battery.
New User
Joined: Jan 2008
Posts: 0
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Am I the only one on the world that has an ammeter that works ?
The problem is the grounding connection at the connector.
My cluster gauges were all wonky when I went on my trip to California.They would pin to the right Fuel,Temp & Oil gauges.
Once I got home I removed the cluster and cleaned everything, It hasn't happened since.
The problem is the grounding connection at the connector.
My cluster gauges were all wonky when I went on my trip to California.They would pin to the right Fuel,Temp & Oil gauges.
Once I got home I removed the cluster and cleaned everything, It hasn't happened since.
Post Fiend
Joined: Jun 2003
Posts: 8,209
Likes: 12
From: Black Hills of SD
Originally posted by Mil1ion
Am I the only one on the world that has an ammeter that works ?
The problem is the grounding connection at the connector.
My cluster gauges were all wonky when I went on my trip to California.They would pin to the right Fuel,Temp & Oil gauges.
Once I got home I removed the cluster and cleaned everything, It hasn't happened since.
Am I the only one on the world that has an ammeter that works ?
The problem is the grounding connection at the connector.
My cluster gauges were all wonky when I went on my trip to California.They would pin to the right Fuel,Temp & Oil gauges.
Once I got home I removed the cluster and cleaned everything, It hasn't happened since.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
The ammeter works on a very small current taken from a shunt in the electrical system. It takes very little oxidation to kill the circuit. The ammeter circuit is not grounded (unless of course you LIKE smoke). All of the connections in these OLD electrical systems have oxidized over the years. Remember these systems were designed to operate for ~5 years. The system Dennis has works because all/some of those connections have been cleaned. The connections to the shunt are welded which leaves the instrument panel cluster connections and meter connections to go bad. Clean those connections, clean and solder any crimp connections, protect them with silicone dielectric b4 you put them back together and your ammeter will work like NEW for many years! -Or at least how they were supposed to work. If the ammeter still does not work there are things that you can do to find the problem with a meter but I won't go into that process here.
Elder User
Joined: Sep 2003
Posts: 794
Likes: 1
From: Portland, OR
Try cutting the 10 guage "batt" wire from your alternator. Your amp guage will go nuts. I spliced 2 alt. harnesses together to make one and had the battery wire go open unknowingly. You'd think with that wire broke the charging system would not work. Actually it still works and bypasses your regulator completely frying your guages and blowing the caps off your new battery. I completely went through another guage cluster and all my guages work perfectly except for oil which I don't have hooked up. My gas guage problems were all in the sending unit itself.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
The ammeter reads the slight voltage differential across a piece of wire. Any wire has a slight resistance and if you pass a current thru it you get a voltage drop. The ammeter reads the voltage drop and the polarity to give you a charge/discharge reading.
If you have a heavily modified electrical system with headlight relays etc etc it helps to just install a voltmeter.
All of your gages will work like new if you just clean up all of the electrical connections. Calibration of a fuel gage is something else tho.
If you have a heavily modified electrical system with headlight relays etc etc it helps to just install a voltmeter.
All of your gages will work like new if you just clean up all of the electrical connections. Calibration of a fuel gage is something else tho.