Early A body Fuel Gauge Instrument Cluster Question.

[cchrishefish]

I am reading over an article on how to install an external voltage regulator on my 64 Dart to allow my dead gauges to function. I would like to know the purpose for the copper tab which is on the circuit board where one of the three fuel gauge studs mount. Is this a ground stud tab? Here is the article with pictures:

Early A-body Instrument Regulators

 

[toolmanmike]

I don't know about the copper tab you speak about but The author of the article mixed up the wires for input and output. The heavy gauge wire should be input and the light gauge wire (4 volts) the output. I wouldn't use 18 gauge for a power feed.

 

[RedFish]

The strange clip on one of the studs is electrical contact, and heat shield, and heat sink. That stud gets pretty warm. So this hole in the board is larger and square. You'll find the housing is cut away a bit larger underneath too. All to vent some heat. By 67 year model they determined warm isn't too hot, so the same pal nut was used on this stud though same round hole, with a backlite cap covering it.
If you'll lift the gauge you'll find a slither of metal on its backside. This grounds the instrument regulator to the inst' housing. Sometimes a lost contact here is the only issue/cause of non working limiter. if you'll install outboard regulator anyway... Cover this slither of metal with electric tape. Now the backfeed condition mentioned in the ill-informed article you referenced cannot happen. Where the switched 12 volt wire serves nothing more than the limiter in your panel, you can take this switched 12 volt wire from harness connector and route it directly to your outboard regulator. Both steps render the original limiter totally isolated. It can't do anything ( dead in a coffin ). If you already opened your fuel gauge to disable the original limiter due to some other web page, you didn't truly need to do that.
Since the heat is no longer an issue, A similar pal nut or common 10-32 hex nut with washer, like those on your amp gauge, will replace that strange clip too.

 

[cchrishefish]

The strange clip on one of the studs is electrical contact, and heat shield, and heat sink. That stud gets pretty warm. So this hole in the board is larger and square. You'll find the housing is cut away a bit larger underneath too. All to vent some heat. By 67 year model they determined warm isn't too hot, so the same pal nut was used on this stud though same round hole, with a backlite cap covering it.
If you'll lift the gauge you'll find a slither of metal on its backside. This grounds the instrument regulator to the inst' housing. Sometimes a lost contact here is the only issue/cause of non working limiter. if you'll install outboard regulator anyway... Cover this slither of metal with electric tape. Now the backfeed condition mentioned in the ill-informed article you referenced cannot happen. Where the switched 12 volt wire serves nothing more than the limiter in your panel, you can take this switched 12 volt wire from harness connector and route it directly to your outboard regulator. Both steps render the original limiter totally isolated. It can't do anything ( dead in a coffin ). If you already opened your fuel gauge to disable the original limiter due to some other web page, you didn't truly need to do that.
Since the heat is no longer an issue, A similar pal nut or common 10-32 hex nut with washer, like those on your amp gauge, will replace that strange clip too.

The slither of metal you mention is the solder point on that stud on the inside of the fuel gauge?

 

[RedFish]

I don't know about the copper tab you speak about but The author of the article mixed up the wires for input and output. The heavy gauge wire should be input and the light gauge wire (4 volts) the output.

The wires are in the correct positions. In reality the wire size doesn't need to be any more substantial that the copper trace on the board. In many cases the copper trace has burned away, served as fusible link. Routing the switched 12 volt directly to the outboard regulator makes the burned open trace a non issue also.

 

[RedFish]

The slither of metal you mention is the solder point on that stud on the inside of the fuel gauge?

No sir. The board on the back of the gauge is held by 2 bent tangs. the slither of metal for chassis ground is also captured here. If you want to lift your temp gauge or any other 2 post gauge from any other panel you will find the housing cut away so the gauges are not chassis grounded. No slither of metal found or required. Only current path is through the 2 posts. ONLY gauge that requires a chassis ground is the 3 post gauge with limiter inside. These housing have a unpainted spot where this slither of metal meets the housing.

 

[RedFish]

And just to clarify... I say slither of metal because it varied with year model. Brass changed to tin at some point.

 

[cchrishefish]

And just to clarify... I say slither of metal because it varied with year model. Brass changed to tin at some point.

Ok, so I can remove that slither piece of metal and just secure that puppy with a nut and be done with it.

 

[RedFish]

Ok, so I can remove that slither piece of metal and just secure that puppy with a nut and be done with it.

No sir. If you pick that slither of metal from under the bent tangs, the board will be loose. Simply cover it with a layer or 2 of electric tape.

 

[cchrishefish]

No sir. If you pick that slither of metal from under the bent tangs, the board will be loose. Simply cover it with a layer or 2 of electric tape.

So, I am confused about your quote "Since the heat is no longer an issue, A similar pal nut or common 10-32 hex nut with washer, like those on your amp gauge, will replace that strange clip too."

 

[RedFish]

So, I am confused about your quote "Since the heat is no longer an issue, A similar pal nut or common 10-32 hex nut with washer, like those on your amp gauge, will replace that strange clip too."

To replace that clip isn't really necessary but it never was a great connector from stud to the board. The limiter is the heat generator. Once it is disabled the clip could be replaced. If you want to attach the 5 volt wire from outboard regulator here you will need to replace the clip with different hardware. At the risk of causing more confusion... the 5 volts is supplied to 2 gauges via the printed circuit board. You can attach the 5 volt wire to the temp gauge post that is on the same copper trace ( as shown on web page you referenced ). Ring terminals under pal nuts has proven to be a "iffy" method. How I do it and recommend, go to Home Depot or any hardware store and buy a small package of 10-32 hex nuts and a package of #10 internal tooth washers ( again just like whats on your amp gauge). With original pal nuts in place, the stud is plenty long enough to place a ring terminal, a washer, and nut on top of the pal nut.
Now allow me to ask a couple questions... I think yours is the braded screen design. if you did open your gauge, How did you open? How will you close?

 

[cchrishefish]

To replace that clip isn't really necessary but it never was a great connector from stud to the board. The limiter is the heat generator. Once it is disabled the clip could be replaced. If you want to attach the 5 volt wire from outboard regulator here you will need to replace the clip with different hardware. At the risk of causing more confusion... the 5 volts is supplied to 2 gauges via the printed circuit board. You can attach the 5 volt wire to the temp gauge post that is on the same copper trace ( as shown on web page you referenced ). Ring terminals under pal nuts has proven to be a "iffy" method. How I do it and recommend, go to Home Depot or any hardware store and buy a small package of 10-32 hex nuts and a package of #10 internal tooth washers ( again just like whats on your amp gauge). With original pal nuts in place, the stud is plenty long enough to place a ring terminal, a washer, and nut on top of the pal nut.
Now allow me to ask a couple questions... I think yours is the braded screen design. if you did open your gauge, How did you open? How will you close?

I just slightly bent it back so I could take a peak inside. I did not drill out the rivets. My gauge is dead it will not respond to any voltage which according to the article the regulator trick will make it function.

 

[RedFish]

If both fuel gauge and temp gauge stopped at the same time, the limiter is the likely culprit. Ohms meter will tell if the gauge is alive or not. 5 volt post to sender post should show approx' 20 ohms. Same for temp gauge.
There is a way to open this type gauge without drilling and replacing rivets/brads. Lets hope you dont need that detailed.

 

[BillGrissom]

I installed an external regulator on my 3 Mopars. Did the cluster on my 1965 C-body a few months ago. I wouldn't use that old thermo-regulator shown since you can buy an adjustable electronic regulator which is much better. Many suggest RTE. Its main advantage is a quick heat-up of the fuel gage, which was an artifact of the old thermal regulator, but costs >$50. If you can tolerate ~1 min for the cluster gages to settle, any 5 V voltage source will suffice. Photo for my 1964 Valiant cluster. I used to find by searching "voltage limiter" with "Plymouth" on ebay, but this year nothing showed. I did find generic 12 V to 5 V adjustable regulators for <$10, which looked like what I had bought for $30 previously. I might buy a big lot and flip them as "Mopar limiters" on ebay. The voltage adjustment lets you get either fuel or temperature gage to read perfectly, but not both. I had to add 10 ohm in parallel with the fuel sender to get both zero and full correct on the gage. Also, test the temperature gage while the cluster is on the bench, using test resistors (chart below). There are slots in the gages to insert a screwdriver and twist to change the zero and range, but likely only done by the gage manufacturer in final testing, so "not advised" though I did tweak mine a little.

I think the TS-18 temp sender I put in my 1965 Dart has 185 ohm at 201F and 3400 ohm at 70 F, but info is sketchy. Since your gage has just tic marks, you can "calibrate yours in place." If you know your thermostat installed, its setpoint should be about the actual temperature once it reaches steady-state, so the corresponding needle position on the dash gage is about 180 F or 195 F, depending. But, the T-stat doesn't control to a perfect setpoint (proportional droop, read an engineering text on control theory), so will settle a bit high if a high heat load (driving up the mountains in summer) or a bit low if freezing outside. You might also use an IR gun reading on the engine block.

 

[RedFish]

A solid state regulator doesn't require the noise capasitor. Leave it or throw it away, makes no difference. The regulator doesn't need to be on the instrument panel either. There really isn't a good place for it, wires conflict with lamp sockets, etc... With a little longer wiring,the regulator can be placed near fuse box or anywhere in the dash. With a common 4 wire trailer harness connector in line, the regulator can plug in and unplug like everything else ( except the amp gauge of course ).
If I pay 50 bucks for that fancy unit with LEDs on it, I will place it where I can see those LEDs.