Recently got the 51 Panel back. It's running. Now working on finishing it. I went through the new wiring and made sure everything is connected properly. Now I'm having trouble getting the gauges to work. When the truck is running, none of the needles move. It's still 6v positive ground. I've checked the grounds. NOS 6v fuel sending unit. Original temp and oil pressure senders.

The Temp needle is at 3/4. The Batt needle is at about the half mark. The Fuel is literally at the letter E. The Oil needle is at the zero mark line.

It's been so long that I don't remember if the gauges ever worked. I've spent two weekends trying to figure this out. I'd like to trouble shoot the gauges. What are the suggestions?

Thanks.

 

Did you say you have done the tests in the Shop Manual? The gauge test procedure starts on page 277.

It might be easiest to check their function if you remove them from the dash.

 

Thanks, Joe. The Battery gauge seems to work. The Temp gauge was at H, but moved to about 3/4 when I turned ignition on. Now it's just the Fuel and Oil gauges. I also went back and checked the grounds. Can't find a ground cable from body to frame. I swear I put one in. I have ground from battery to engine block and engine block to frame. I doubt it, but I wonder if adding a body to frame ground help with the two gauges not working.

 

I would instead add a ground to the cab, at the firewall. The cab is insulated with rubber from the frame, the only real "connection" is via the radiator saddle.

First thing to check is to see if there's power to the gauges, but if your temp gauge now works, you must have it.

 

I ran a 12 gauge ground wire from my engine, which is connected to the + battery terminal by way of that super cable I got from you, to the fuse panel ground bus, which is grounded to the cab. How's that for a run on sentence?

You might have 2 separate problems for those two gauges. Check your fuel sender operation and ground for the gas gauge. I don't know about the oil pressure.

 

Ilya,

Have you had any resolution to the gauge issues? I've just been through the gauges section in the shop manual and may be able to offer some suggestions and information.

First, the ammeter (not battery). Until some time in the mid- to late-'50s the state of the electrical system was monitored not by reading system voltage, but by determining the state of charge or discharge (current in amperes). There should be a loop of wire on the back of the ammeter with a yellow wire running though it. That wire runs from the 30 amp circuit breaker to the battery terminal on the starter relay. That wire is necessary for the ammeter to work since the coil of wire induces a voltage for the meter proportional to the current flowing through the yellow wire. To test the ammeter, turn on the headlights with the engine off. The needle should deflect toward the D (discharge) side of the meter. If it doesn't look for the yellow wire or a break in the coil of wire on the ammeter. The needle should also move toward the C (charge) side when you rev the engine if the generator and voltage regulator are working properly. If the needle's just sitting centered in the gauge and doesn't move either direction it's not working.

Next, the fuel, oil pressure, and water temperature gauges. Ford used a weird (to my mind at least) method of operating these gauges. Instead of using resistive sending units like modern cars (and many back in the '50s) they used bimetal units very much like older furnace thermostats. Without getting too much into how bimetal works in the sending units, the more fuel, heat, or pressure you have, the longer the contacts in the sending units stay closed. The gauges also have bimetal movements that heat to the same temperature as the bimetal in the sending units which causes a deflection in the needles of the gauges.

There are 4 things that could cause your gauges to not be functioning properly. First could be that the gauges don't have a good ground. I'm hoping you've already looked into that and taken corrective measures if necessary. Since you're having problems with all of the gauges, I'd start here since it's the only thing common to them all. Also be aware that the sending units themselves need to be properly grounded. Check to make sure you have a good ground at the fuel tank and sending unit and a good ground to the engine. Also check to see that there is no teflon tape or other insulating material on the threads of the temp and pressure sending units.

Second could be breaks in the wires connecting the sending units and gauges or wires with high internal resistance from fatigue or corrosion. You can use an ohmmeter to check the wires which should have no more than 4 or 5 ohms of resistance. If your grounds are good, check these out.

Third could be the sending units themselves. Ford's diagnostics for this (on page 278 in the shop manual with corresponding figure 93 on page 280) involves disconnecting the wire from the sending unit at the bullet connector on the gauge. Then hook that gauge terminal up to one side of a 50 ohm variable resistor (you can use the center terminal of a potentiometer) and then hook the other terminal of the variable restore (one of the outside potentiometer terminals) to ground.Make sure the resistor is set to maximum resistance before connecting it to the gauge. Then put the test leads from a volt meter across the gauge terminals. Turn the ignition on and adjust the resistor until the volt meter reads 1.5 volts. At that setting the needle on your gauge should be at about half scale. If it is, the gauge is working properly then the problem is either with the sending unit or the wiring. This procedure is the same for the fuel, oil, and water gauges.

Fourth is a problem with the gauge. Here Ford punts and tells you to hook up a known good gauge to see if that works. The only way to know that the gauge is good is go through the procedure above.

I really hope I'm too late and that you've found the issues. In any case, this may be of some use to others.

- Glenn