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Question on a 66s gauges and instrument voltage regulator?


FBBO Gold Member
FBBO Gold Member
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4:56 PM
Jan 28, 2012
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Last year I went thru my gauges and installed a solid state voltage regulator. Since then my gages have worked well and read accurately except for one thing. After I have driven the car a little and shut it of, say to get gas, when I restart the car the fuel and temp gage go to full right position and then migrate back to normal over about a 10 sec period. This isn’t just normal heat soak shutting an engine off, it pegs full right along with the gas. I haven’t paid attention to see if they do this on a cold start but it’s sort of bothersome enough on a warm restart to make me question it. The engine and dash harness are all new.

Anyone experience this before? Try another voltage limiter?
Newer cars do this intentionally to wipe off any dust and corrosion so they work well when/if they do get pegged during normal use.
If it's repeatable (doesn't get any worse) and it hasn't harmed the gauges then it might actually be a good thing.

But a bit odd. The normal "regulator" would do something similar as it cycles based on heat so it would be on for maybe 10 seconds initially like you describe.
The gauges have a lot of averaging built in to accomodate the points type regulator.
I forgot to mention that I have a 67 too and it doesn’t do this. The temp gauge will go up a little for a minute or two upon restarting it when it’s hot from heat soak but not much.
I tried it on my car after it sat overnight - turned the key to run position. The gas gage rose smoothly all the way over to full and then settled back to 3/4 full which it is. The temp gage didn’t budge - maybe due to high resistance of cold sender??? These are stock gages.

Anyone experience this, maybe due to solid state instrument voltage regulator?
Hopefully your temp gauge isn't open circuit.
If you don't want to run the engine you could heat it up with a heat gun.
The rt-eng.com IVR puts out a consistent voltage for about two seconds when powered from off to on. After that the device enters "breathe" mode which pulses voltage from 0 to 5V at a 1 or 2 second rate.

The reason for this is the gauges are thermal operated just like a turn signal flasher. The heater wire bends the bi metal strip which swings the gauge indicator. The consistent voltage at power up is to get the gauge heater up to operating temp so it can measure properly.

BTW the rt-eng.com IVR mimics the old IVR as they too are thermal bi metal switches and just like a turn signal flasher in operation.
New sender and temp gage matches my IR thermometer and mechanical, under dash temp gage as close as you could expect.

So Billccm, if I understand correctly it sounds like this is normal performance for a solid state instrument VR.

I installed one in my Charger last spring and it doesn't make the gauges go full scale.
Mine do not do that with a new Rte IVR installed. They just creep up to where they belong like an old OE VR.
@dadsbee and @Don Frelier are correct. The 2 seconds of consistent voltage is just to get some heat into the bi metal to start accurate measurements. This is not intended for a full scale swing.

Man, it’s always something with these old cars. Sounds like I probably need to get a RTE voltage limiter. Always good to support an Arkansas company anyway.

Actually it was a National Standard part off Amazon. But I’ve ordered one from RT Engineering.
Got the IVR from RTE installed today and it took care of the issue with the gages - no more full sweeps when starting the car. Reading their literature it provides a number of benefits and safeguards so a nice product.
Good people and great engineers at RTE. Their tach driver board is a nice upgrade to the factory tachs and they work well with MSD.