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Discussion Starter #1
my 4 status gauges are dead. temp, pressure, volt, fuel. only ones that do not work.

So I've found a good wiring diagram for all of the pin numbers, and there appears to only be one continuous ground from the cluster, but each switch has it's own ground on the engine or switch/sensor etc. All of my other indicators are working, speedo, tach, direction arrows, hazards, door buzzer. She runs and drives, and it looks like pin 6 is to the ignition coil, so I am guessing she wouldn't run and drive if it were completely shot?

typically if there are 4 pieces of equipment in the same area, I lean towards there being a common issue, but seams that may not be the case here? Do the 4 gauges and only the 4 gauges share the same power source or something?

and will the truck run if I unplug the gauge cluster to check powers/grounds through the pins?
 

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It's been a while since I've looked at the PCB paths, but my first guess is you may have an issue with the voltage regulator on the back of the cluster. But I'll have to see if I can dig up my pinout to see if that would be a common point for those four meters.
 

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Discussion Starter #3
It's been a while since I've looked at the PCB paths, but my first guess is you may have an issue with the voltage regulator on the back of the cluster. But I'll have to see if I can dig up my pinout to see if that would be a common point for those four meters.
I tried but could not find a diagram of the PCB, and the pictures on JBGY for the part is only the unprinted side, so I can't even try to follow the paths to figure out a common point.
 

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yo Jimmy,
164496

The oil pressure and temp gauges have their grounds via their senders. I haven't been able to find info on the other two, YET?

The IVR can fail two different ways. it will quit working altogether, thus none of the gauges will work. Or two, it will stick, and the gauges will peg to the extreme right, then it will unstick and fall back to normal. The IVR is a pulse type. The voltage is regulated by how fast the pulses are. When it sticks, it doesn't pulse, etc... Try tapping on it. Make sure the cluster ground is in good shape. If the IVR isn't grounded or has an intermittant ground, it wont pulse like it should either.

Suggest getting one from a Yard; Since there are about 12 different types, make sure to take the old one with you; Fits: 1971/86 F100/350; 1971/91 Econoline; 1978/86 Bronco; 1977/79 LTD II/Ranchero/Cougar/Thunderbird without Tachometer; 1972/76 Thunderbird/Continental Mark IV; 1971/72 LTD/Mercury Marquis for MOTORCRAFT Part # GR513 (D1AF10804AA, D1AZ10804A)..."
Source: by miesk5

Instrument Voltage Regulator (IVR) in78-86; Back in the early 60's when Ford originally decided to go to a 5 volt system for the instruments the electrical engineers were faced with the problem of providing the guage
149241

s with 5 volts. To make a true voltage regulator with 60's era parts would have been extremely expensive and the final product would have been about the size of a bread box. No good for their purposes. But since the guages are a hot wire design that doesn't respond very quickly to changes, the engineers were able to fool the guages into thinking that they had 5 volts by pulsing 12 volts to the guages. With the technology that is now avalible the IVR can be replaced with solid state components that supply a true 5 volts to the guages and put a stop to the wild dance of the guages
 

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Discussion Starter #5
yo Jimmy,
The oil pressure and temp gauges have their grounds via their senders. I haven't been able to find info on the other two, YET?

The IVR can fail two different ways. it will quit working altogether, thus none of the gauges will work. Or two, it will stick, and the gauges will peg to the extreme right, then it will unstick and fall back to normal. The IVR is a pulse type. The voltage is regulated by how fast the pulses are. When it sticks, it doesn't pulse, etc... Try tapping on it. Make sure the cluster ground is in good shape. If the IVR isn't grounded or has an intermittant ground, it wont pulse like it should either.

Suggest getting one from a Yard; Since there are about 12 different types, make sure to take the old one with you; Fits: 1971/86 F100/350; 1971/91 Econoline; 1978/86 Bronco; 1977/79 LTD II/Ranchero/Cougar/Thunderbird without Tachometer; 1972/76 Thunderbird/Continental Mark IV; 1971/72 LTD/Mercury Marquis for MOTORCRAFT Part # GR513 (D1AF10804AA, D1AZ10804A)..."
Source: by miesk5

Instrument Voltage Regulator (IVR) in78-86; Back in the early 60's when Ford originally decided to go to a 5 volt system for the instruments the electrical engineers were faced with the problem of providing the guage

s with 5 volts. To make a true voltage regulator with 60's era parts would have been extremely expensive and the final product would have been about the size of a bread box. No good for their purposes. But since the guages are a hot wire design that doesn't respond very quickly to changes, the engineers were able to fool the guages into thinking that they had 5 volts by pulsing 12 volts to the guages. With the technology that is now avalible the IVR can be replaced with solid state components that supply a true 5 volts to the guages and put a stop to the wild dance of the guages
So, I haven't tapped on the IVR yet. my oil press gauge goes halfway then slowly falls back. my temp and gas gauge are dead. I applied voltage to all 3, all gauges work. I checked voltage on them with it hooked up and running and I was getting pulses.

ok, I think that the IVR is good. if I ground out the sensor side of each gauge, they all go to max and hold. just to test tomorrow when I have light again, I'll ground out the temp sensor at the sensor and make sure the gauge goes to full peg. But I did check it for voltage there and I was getting similar pulses as I am at the IVR and gauges
 

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Discussion Starter #6
So, it ended up being each individual sensor, instead of a combined circuit. atleast that is what it looks like. I have to go buy a 12 point socket to do the oil press send unit tomorrow, but the coolant temp is working now. and the fuel sending I will have to burn some gas, not lowering a tank with 30 gallons of gas in it.
 

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Discussion Starter #7
now I feel like the worlds dumbest ex-electrician current mechanical engineer.

the reason the oil pressure sender wasn't working was because the PO had put teflon on the threads so it wouldn't seize. this also prevented there being a good ground from the sender to the block.
 
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