Wacked Out Gauges

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33plym

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Milwaukie, Oregon
Just purchased at 1966 Barracuda & found that the gauges work but accuracy is another issue. Temp gauge goes from "peg" left "cold" to peg right "hot" after running for a couple of minutes. Drove it on a 1700 mile trip with no overheating issues. Gas gauge starts at empty, sometimes moves to full & then drops to empty, Oil pressure gauge slowly rises from low to high & stays pegged. Alt gauge starts barely on the charging side & within a couple of minutes shows discharging the balance of running. No notice of slowing or dead battery. I was looking at a dash removal and disassembly video on the internet and noticed a small capacitor/condenser looking thing plugged into the gas gauge called a "Instrument Power Regulator". Would this be causing my gauge problems? Any other suggestions? Thanks all.
 
If all the gauges are acting up, it is likely you IVR (Instrument Voltage Regulator is the common name I believe). I don’t know where it is on an early A, but they are available aftermarket.

If the gauges are pegging, you are likely in danger of damaging them.


Edit: I meant all but the amp gauge....
 
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33plym said:
Just purchased at 1966 Barracuda & found that the gauges work but accuracy is another issue. Temp gauge goes from "peg" left "cold" to peg right "hot" after running for a couple of minutes. Drove it on a 1700 mile trip with no overheating issues. Gas gauge starts at empty, sometimes moves to full & then drops to empty, Oil pressure gauge slowly rises from low to high & stays pegged. Alt gauge starts barely on the charging side & within a couple of minutes shows discharging the balance of running. No notice of slowing or dead battery. I was looking at a dash removal and disassembly video on the internet and noticed a small capacitor/condenser looking thing plugged into the gas gauge called a "Instrument Power Regulator". Would this be causing my gauge problems? Any other suggestions? Thanks all.
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Thanks for the input - I'll hit a parts store ASAP.
 
IVR is in the fuel gauge. I wrote an article about this on my 66 a bout 2 years back and how to remove the factory unit and install a modern digital unit.

Now.... where the heck is that - it had pictures.
 
Gauges go to full tilt!?!
Electrical and Ignition
Here it is. Not really an article but a post doing the same issue. Link is not working. Copy and paste in search and it will come up.
Good luck! Take your time- pretty easy once you know how.
Syleng1
 
Wouldn't a poorly grounded cluster cause all the gauges to act up? I was under the impression the IVR only affected the fuel and temp gauges. I know on my car when the ground on the fire wall was broken the gauges acted really odd.
 
Poor ground and I believe the gauges go full tilt. Issue is op need to do some leg work and can decide from there what is the issue.
 
Mike69cuda said:
If all the gauges are acting up, it is likely you IVR (Instrument Voltage Regulator is the common name I believe). I don’t know where it is on an early A, but they are available aftermarket.

If the gauges are pegging, you are likely in danger of damaging them.
Click to expand...
The fuel gauge IVR would handle all but the ammeter. The fact that is acting up is another issue. The older (55 years in your case) cars have likely had a LOT of hands in the pie, so fixing things like this will simply take time and patience.
 
You should have a mechanical voltage limiter inside the 3 post fuel gauge. The capacitor attached there prevents a pop noise in radio speaker. A failing limiter will send too much power to the gauges and can damage them. Sometimes the limiter completely shorts out. Then the copper trace on the circuit board that carries 12 volts to that limiter will burn open like a fusible link which saves the gauges. Replacing the limiter with solid state regulator is the fix.
 
33plym said:
Alt gauge starts barely on the charging side & within a couple of minutes shows discharging the balance of running. No notice of slowing or dead battery.
Click to expand...
As mentioned above the "alternator gage" is completely seperate from the others. Assuming the wiring hasn't been screwed with, its wired directly into the battery feed. If its centered when the engine is off ( all lights off including dome and brake lights) then it should be centered when the battery is completely charged. Anything else indicates battery charging or somebody added electrical something to the battery side of the ammeter.
Battery charging could be due to low or damaged battery, excessivly high alternator output voltage, poor alternator output, or resistance in the the alternator output line. Quick way to narrow that down with minmal tools is:
1 Engine off, measure battery voltage.
2. During starting measure battery voltage.
3. During fast idle idle or at 1250, measure battery voltage AND measure output voltage at the alternator. If the voltages are different, measure the votlage at the regulator input connection (blue wire). Note the alternator gage reading. (scale is 40 amps discharge to 40 amps charging, estimate from that).
4. At slow idle measure battery voltage AND measure output voltage at the alternator. If the voltages are different, measure the votlage at the regulator input connection (blue wire). Note the alternator gage reading.

Write down the results and we can tell you what they add up to. Please don't guestimate.
 
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