66 barracuda gauges: 2 questions..

[Miranthis]

1) Looking at my stock of circuit boards for my 66 Cuda dash cluster and there are ones with a dark blue conformal coating and ones with a dark green one. The examples I have all have the same part number (2587 243) and S.W. 816656. I do not see any revision numbers on either color board. Are those just different suppliers?

2) The gas gauge is the voltage regulator for the Gauges as the Gauges work at 5V (?). The regulater voltage feed comes from the 'third pole' of the gas gauge; the top one, correct? 12 V comes in from terminal A, the black wire from the fuse block. The gas gauge feed is on the blue wire, terminal B. Does the Gauge ground to the frame of the cluster? So if I probe the voltage from the 3rd pole of the gauge to ground I should get 5V, correct?

 

[Mattax]

Maybe two suppliers or maybe a running change or maybe a reproduction.
FWIW the ones in my 1966 built Model year 67 are blue.

2) The gas gauge is the voltage regulator for the Gauges as the Gauges work at 5V (?). The regulater voltage feed comes from the 'third pole' of the gas gauge; the top one, correct? 12 V comes in from terminal A, the black wire from the fuse block. The gas gauge feed is on the blue wire, terminal B. Does the Gauge ground to the frame of the cluster? So if I probe the voltage from the 3rd pole of the gauge to ground I should get 5V, correct?

Power to the instrument voltage regulator connects at the I terminal. I = Ignition. (your A)
Key in run position, the "Ignition 1" circuit is hot. I doubt the branch is fused. Check the FSM
I'd have to look at the diagrams again, but some years may power the instruments using the Accessory circuit, then it would be on with key in run or accessory. Even so, doubt its fused.

Current flows out the S terminal to the fuel Sender. (your B)

Intermittant current flows to the other gages (Temperature and Oil Pressure) on the board. It pulses creating an average of roughly 5 Volts.

The center of the gage is the ground contact.

 

[Mattax]

According to the FSM, the power comes from a junction in the accessory circuit.
Q2 is the accessory circuit.
G1 is the branch that feeds the gage cluster.

"Battery - J1" Is the power into the key switch.
Battery means that circuit is connected to the battery and is always hot.
This is accepted term even though the wire J1 branches from the alteRnator output wire R6.
Once the car is running, power comes from the alternator.

See this thread about testing gages on '66 Barracuda

66 Barracuda gauge problems

Gday everyone, Posting from Australia. I have a '66 Barracuda imported here 20 years ago. Poor thing has had a rough, unloved life, but it's a formula S and very few of those here so I thought it was worth saving. So 20 years of life gets in the way of getting this car up and running but...

www.forabodiesonly.com

It will get you to videos and service tech bulletins.

 

[cudamark]

I have both blue and green boards too. I've interchanged them without issue.

 

[Miranthis]

Intermittant current flows to the other gages (Temperature and Oil Pressure) on the board. It pulses creating an average of roughly 5 Volts.

Ahhh... that is exactly the basis of my question on the regulated voltage, as I kept getting an ever-changing voltage reading. Was expecting, i suppose, a solid 5V out of the regulated voltage line, but i have to keep reminding myself this is not even a 1970's electronics projects, but a mid-early 1960's one .

The center of the gage is the ground contact.

Which is what i thought as well, but the inside of the instrument cluster has that patch where the gauge center contacts still painted, I would have thought a ground contact would be metal to metal to avoid inconsistent grounding.

Each of the gauges - oil pressure, gas, and temp - are grounded to the block (in the case of the gas gauge, the fuel line ground strap grounds the inlet tube/sending unit circuit to the fuel line, to the block at the carburetor, etc.), and then the ground strap to the firewall completing the circuit

 

[Mattax]

the inside of the instrument cluster has that patch where the gauge center contacts still painted

Lets see it.

Does it not look like this ?

ach of the gauges - oil pressure, gas, and temp - are grounded to the block (in the case of the gas gauge, the fuel line ground strap grounds the inlet tube/sending unit circuit to the fuel line, to the block at the carburetor, etc.), and then the ground strap to the firewall completing the circuit

Im sure you mean the senders are grounded.

 

[bcschief]

All gauges with 3 terminals have the IVR built into that gauge, it varies by the year make and model. My 63 Valiant is built into the fuel gauge but I know some cars are built into the temperature gauge and maybe some are in the oil pressure gauge. At some point they made them external on the rear of the cluster.

 

[cudamark]

The gauges themselves don't need to be grounded. Those two bent over tabs just hold the insulation plate in place. The housing does need to be grounded however for the dash lights to work. If you have the stock built-in IVR that's part of the fuel gauge, I would recommend that you do the solid state upgrade to eliminate that. Usually when the stock one goes bad, it sends a full 12-14 volts to the gauges which will fry them.

 

[Miranthis]

Lets see it.

Does it not look like this ?

Im sure you mean the senders are grounded.

The circuit that goes through each gauge is grounded....as in you have to have a complete loop in order to function.

 

[bcschief]

The circuit that goes through each gauge is grounded....as in you have to have a complete loop in order to function.

The sending unit is the ground the only exception would be the amp meter.

 

[cudamark]

The gauge itself grounds through a potentiometer in the sending unit. That completes the circuit, heats the coil in the gauge to a certain point, which heats and bends the bi-metal strip that attaches to the needle. The gauge housing doesn't need a ground as it isn't in the circuit.

 

[cudamark]

You can test any of those gauges just holding it in your hand. No ground needed.

 

[Miranthis]

You can test any of those gauges just holding it in your hand. No ground needed.

Even to measure resistance you do need to place the gauge in the circuit betwen the measuring meter leads, on to the red lead and one to thr black lead. Gotta complete some circuit to get any information out of the circuit.

 

[cudamark]

Even to measure resistance you do need to place the gauge in the circuit betwen the measuring meter leads, on to the red lead and one to thr black lead. Gotta complete some circuit to get any information out of the circuit.

Correct, but, nothing goes through the housing....especially on an ammeter.

 

[Miranthis]

Lets see it.

Does it not look like this ?

Im sure you mean the senders are grounded.

Well, after checking my factory set (that I know has not been messed with) I see that it IS bare metal so that patch makes contact on the back of the gas gauge to ground. The donor I picked up has been repainted, judging by overspray on the blue bulb covers....

 

[Miranthis]

According to the FSM, the power comes from a junction in the accessory circuit.
Q2 is the accessory circuit.
G1 is the branch that feeds the gage cluster.

"Battery - J1" Is the power into the key switch.
Battery means that circuit is connected to the battery and is always hot.
This is accepted term even though the wire J1 branches from the alteRnator output wire R6.
Once the car is running, power comes from the alternator.

I have the FSM, but find that the 11x17 color non-factory wiring diagram comes in very handy with my (i refuse to admit) older eyes...it gives letters to the pins on the round connector that I referenced

I did find an error in the original version he sent and he made the correction and sent me a new one. Error was in the Y and X connection on the cabin side of the bulkhead connector... he had a couple wires exchanged...

 

[67Dart273]

It may be that only the fuel gauge, because of the IVR, needs to be case grounded. The way to tell is to measure resistance from the three studs to the case.