instrument cluster voltage regulator - Vintage Mustang Forums

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post #1 of 4 (permalink) Old 08-05-2013, 12:27 AM Thread Starter
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instrument cluster voltage regulator

Hi all I am a long time viewer of these forums, but first time poster.
I have never had to post before because I can usually find my solution, but this time I can't seem to find anything. Well I have a 66 mustang with modern after market gauges (would of loved to keep stock but previous owner butchered the wiring beyond repair) and I just wanted to know if I need the instrument cluster voltage regulator. My original one died so I just straight connected the gauges to the gauge feed on my ron francais fuse box. I removed the regulator when I got my new fuel gauge and sending unit because I had to wire that up anyway, but since then my gauges keep swinging back and forth real fast randomly and occasionally twitch in small sweeps. Tomorrow I am going to recheck grounds but I really didn't change those up so I suspect not having the regulator is the culprit. Sorry for long post but help is much appreciated
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post #2 of 4 (permalink) Old 08-05-2013, 07:35 AM
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Do not use a IVR with aftermarket gauges. The IVR drops the instrument voltage down to ~5volts, and aftermarket gauges require a full 12V. If your aftermarket gauges are bouncing around, you may have a bad connection or a short somewhere. Get a hand held volt meter from Radio Shack or elsewhere and check the voltage going to the gauge.


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post #3 of 4 (permalink) Old 08-05-2013, 07:39 AM
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That depends on your "aftermarket" gauges. If they need 12v to run on, then they only need to be wired to a switched 12v source and have a reliable ground. If they use 5V, they need to be connected to the original IVR or have their own 5V regulator. Since you've removed the IVR and the gauges appear to work some of the time, that doesn't seem to be the problem. In either case, a volt meter will tell you plenty.

There should be no voltage reading on the low or ground side of the gauge. If you find a voltage, the ground is the problem. There should be at least 12v on the hot side with the car off, over 13 when it's running, and it should be stable. If that voltage is drifting, check the wiring from the gauges back to your fuse block and check the voltage at that point as well.

For a suspect ground, use a heavy clip lead and run a redundant ground from the car's body to the ground side of the gauges. Do the same for feeding 12v into the cluster from a known good 12v source.


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post #4 of 4 (permalink) Old 08-05-2013, 02:43 PM Thread Starter
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I will check those things out and let you guys know how it went. Thanks for the help
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