62 fuel gauge problem

[Mike P.]

My fuel gauge is not working. Should the gauge be grounded to the gauge housing? I installed a new temp. gauge along with the housing. After re-installing both gauges I discovered that when the key was turned on both gauges pegged and I could hear a clicking noise coming from the sender. I removed the fuel gauge and installed an isolator so that the gauge would not contact the housing. I checked both gauges with an ohm meter and found no ground continuity between the terminals and housing. I started the engine and could see that the temp. gauge was working, but not the fuel gauge.
Mike

[Richard M.]

Re: 62 fuel gauge problem

Mike,

Yes the fuel gauge case should be grounded to the gauge pod, which then gets grounded when held in with the 2 attaching nuts to the cluster, via the Black/White wire in the harness. From the rear, the right terminal is the Pink Power lead which comes from the Ignition switch. The left terminal is the Brown wire from the sender.

When the Temp gauge pegs, it's a indication that it's sender terminal/wire is hard grounded.

When the fuel gauge pegs right(F), it's a indication that the sender/terminal wire is open circuit. Grounding the sender/terminal will peg left(E).

The back of the fuel gauge "meter", should be grounded to the pod housing. If you repainted the pod, make sure the paint is removed behind the meter, as well as the tabs for the attaching nuts. In the photos below, you can see the metal plate where the tiny coil wire attaches. That coil wire must be grounded..... it gets it from the backside of the meter from that flat plate touching the gauge pod. The studs get isolated from the case by using that tan cardboard insulator. Note it's stamped "SENDER" and "IGN" .

Metal plate at rear must be grounded.
P6210115.jpg


Orig type Fuel meter on right showing metal ground plane on back. (repro left)
P6210118.jpg

Backside of pod, fuel gauge on right(rear view). Right terminal is IGN, left is SENDER(with torn red tag)
P6210120.jpg

Rich

[Mike P.]

Re: 62 fuel gauge problem

Rich,
Thanks for responding. I will pull the cluster and remove the isolation from behind the fuel gauge. The pod is new and when the fuel gauge was in place it was grounded before I added the isolation. Because of poor grounding, I previously ran a new ground from the sender to the frame. My turn signal was causing the fuel gauge to jump. After adding the ground it worked properly. Should the B/W wire ground the cluster?
What could have caused the sender to make a clicking noise when the key was turned on ?
Mike

[Richard M.]

Re: 62 fuel gauge problem

Mike,

The "clicking" sound you heard from the fuel sender is alarming. I have never heard of that happening before. It could be due to that "floating" ground at the meter, but a open circuit in a analog type meter/sender system will result in non-operation, not a clicking sound. Is it possible the sender wires were loose, causing a intermittent?

If the sender wires are reversed, it can cause a failure in the sender and/or meter by reversing the polarity, and burning the sender resistor coil and meter coils. I have never "experimented" doing that with a tank occupied with fuel for obvious reasons.

Yes the Black/White tracer wire in the dash harness is ground, and grounds the cluster. Any wire added to help fuel sender/tank ground eventually ties to all grounds involved. It is sourced from the heavy gauge wire at the left rear inner valve cover attach screw, also Blk/Wht. In the harness, it's also joined to the Black/White going forward to the headlight harness wiring, and also to the rear harness for the fuel tank ground and the rear lights ground. There is also a Black/White at the rear bumper mount(frame) which ties back to all Black/White ground wires in the harness also.

That Black/White for the cluster has a ring terminal, which is connected at one of the lower(right rear) studs which mount the speedometer. It can actually go on any stud, provided it's a good tight connection, but originally it's tied to that position mentioned.

You said the gauge pod was new. A reproduction or a "restored" unit from elsewhere? Some restored units I've seen are painted completely, and they paint over the area where the meter ground plane is located. If so, clean the paint. If it's a repro "plated" pod, it should be fine, but check with a ohmmeter to be sure.

Good luck, but be extra careful with the wiring and a tankful of fuel. While you have the gauge pod out again, you can test on the bench with a 12v battery and a "simulated" sender. Check out this thread for a procedure to use. If you can get a few 100 ohm resistors you can check your pod and gauge out of the car. About 100 ohms will give you "F", tie them together in parallel(50 ohms), and it'll read about "Half", zero ohms(ground the sender terminal), will be "E". Post 7 and 10 has a test procedure and pics. This was for a reproduction digital gauge, but is the same test setup for the original analog gauges too.

https://www.forums.ncrs.org/showthread.php?104599-1960-to-1962-Reproduction-Fuel-Gauges-Failures

Rich

[Mike P.]

Re: 62 fuel gauge problem

Rich,
I pulled the instrument cluster again. I'm getting very good at removing and re-installing. I removed the isolation from the fuel gauge. I got continuity between the pod housing and terminals on both the fuel and temp. gauges. The new pod had bare metal were both gauges would make contact.
I checked for the gound wire from the left rear of the engine and found the ground attached at the member which the parking brake bracket is bolted to. Should I run another wire from that point to the speedo housing stud. I found that the continuity between that point and where the cluster attaches with five bolts to be good.
As for the clicking noise, I have no idea. I attached an ohm meter between the sender and it's ground. I was reading around 25ohms. When I pushed on the side of the car the reading flucuated up to 30 ohms. I was curious why there was a clicking noise so I pulled out the sender. Obviously, there was nothing there to make this noise. Prior to removing it, the terminals were tight. Without engaging my brain, I conducted a bench test by applying 12 volts from an external source. I have a new sender coming! Once I receive it I perform a simulated bench test.
Mike

[Richard M.]

Re: 62 fuel gauge problem

Mike,

I may be reading your explanation wrong, but......you say that you "have continuity between the pod housing and terminals on both the fuel and temp. gauges." That should not be. Maybe your wording didn't explain what you meant to say. The brass terminal studs for both gauges should be insulated from the pods. The cardboard insulators need to be on the back of the pods, before the attaching nuts are installed. Only the ground planes on the meter backs should have ground continuity to the pods.
edit....Maybe it's not 0 ohms continuity your getting. You will read low ohms through the meter coils to ground, so maybe that's what you're seeing. You should not get a dead short to the terminals.

Yes, I'm afraid you destroyed your sender by putting 12 volts across it's mount plate ground, and the sender terminal.... on the bench. It's a good thing it was out of the tank. You needed to test it with a ohmmeter instead. Caution is very important when testing this circuit. It's only a wire-wound resistor in the sender, apx 90 ohms, so it burned it out. When you were reading 25 ohms with it in the tank, you had about 1/4 tank of fuel. By moving the car around and sloshing the fuel around, the mechanical lever and float may be making that noise like the clicking you heard, but it should not make noise electrically.

The Ground....Someone before you attached the Cluster ground to the park brake attach bolt? Eventually, via the cluster attache bolts, it will get to the cluster, but it's not the proper ground path. It relies on too many bolts to get to the cluster via the metal reinforcements. I would remove it from the PB bolt and attach to the back of the cluster. It doesn't need to go to the speedo mount stud though. It can go to any stud that accessible. It's tricky to get it on the speedo stud. It's the way it was originally, but electrically it can go on any clean metal attach stud.

I've sent you a email with my phone number. When you get your new sender, or whenever, feel free to call me so we can talk over some of this. The fuel gauge and sender can be confusing so it may be better to talk live.......if you prefer.

Rich

[Mike P.]

Re: 62 fuel gauge problem

Rich,

Thanks for your help. I bench tested the new sender and fuel gauge. It worked great. After re-installing the cluster all systems worked.
Best Regards,
Mike

[Ken A.]

Re: 62 fuel gauge problem

FWIW, 62 & back senders operate from 0 to 30 ohms, not 0 to 90 ohms.

[Richard M.]

Re: 62 fuel gauge problem

FWIW, 62 & back senders operate from 0 to 30 ohms, not 0 to 90 ohms.

Yup, I seem to always get the resistance value of C1 & C2 senders confused. Thanks for clarifying Ken.

Rich,

Thanks for your help. I bench tested the new sender and fuel gauge. It worked great. After re-installing the cluster all systems worked.
Best Regards,
Mike

Glad it worked.

Rich