Temp and Oil Gauges overreacting

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31 Model A Station Wagon “Woody”
69 Mach 1 - 351C
72 Mach 1 - 351C
96 Cobra Convertible
Recently I pulled the radiator and had it cleaned out and reinstalled it. Since then, the temperature gauge and the oil pressure gauges seem to read pretty high. The oil has always gone to the high side, but even higher now. The temperature gauge is the one that scared me as it goes to the end of the scale, sometimes over. I used a infrared temperature sensor to measure all around and the car is not overheating, in fact it is quite comfy at 160-165 all around on external surfaces. It’s weird because it coincides with the radiator service, but it is probably something else. Any advice?
 
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My all time favorite vehicle is our 1969 Shelby GT500
I have a feeling you may have oil and temp sending units made for idiot light, not for analog gauges. The idiot light sending units have a simple Go/No Go sending unit circuit, whereas their analog gauge related counterparts will report a "degree of" measurement change throughout their entire range.

Getting an infrared thermometer is a great first step, but I have found it I am more than 8-12" away from the object I am checking temp on, the reading will begin to get lower as the thermometer InfraRed sensor is impacted by relatively cool air between the the thermometer and the target object.

Another possibility is the sending unit wire(s) got pinched and grounded. It is also possible your Instrument Voltage Regulator (IVR) has failed. The IVR is attached to the back of the Instrument Panel, and in nearly all cases it required the instrument panel removed.

While the panel is off you may be tamped to replace the old incandescent illumination bulbs with LED lights (which are far brighter). That is a good move, but there are a few things you need to be aware of. First, unlike incandescent bulb, LED lights are polarity sensitive, so if one (or more) do not work when installed, just remove the offending lights, rotate their position into their panel holes by 180 degree, and try them again. Also, LEDs are far brighter than their incandescent bulb, so you may find the LED lights to be a bit brighter that you want. I have read that the conventional dimmer (rotating the headlight switch shaft clockwise or counterclockwise) does not work with LEDs, but their may be circuitry options to allow the LEDs to be dimmed. I have never needed to do this, but I keep that tucked into the back of my mind/

Attached are some PDF files that may be of help to you.
 

Attachments

  • Remedy for those 71-73 Stang Dash Lights_ _ Vintage Mustang Forums.pdf
    3 MB · Views: 12
  • 1972Mustang_InstrumentPanel_FuelGauge_Circuitry_20211031.pdf
    4.7 MB · Views: 2
  • 1971Mustang_InstrumentPanel_FuelGauge_Circuitry_20211031.pdf
    6.6 MB · Views: 2
  • ChristopherNeal_71-73Mustang_DashLightsFuelGaugeInoperative_20201005.pdf
    6.9 MB · Views: 2
  • 1973Mustang_InstrumentVoltgeRegulator_20210428.pdf
    5.2 MB · Views: 3
  • 1973Mustang_DashIlluminationLightCircuitInfo_20210418.pdf
    5.9 MB · Views: 7
  • 1973Mustang_OilPressureSwitch_BrakeWarningLight_Sircuit_20210419.pdf
    4.1 MB · Views: 7
Joined
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My all time favorite vehicle is our 1969 Shelby GT500
I have another PDF that hows the 1973 Mustang electrical schematic and a lot of related info. It is too large to attach to this message. If you would like it please email me at [email protected] and ask for the 1973 Mustang file named:
1973Mustang_InstrumentGauges_WiringSchematic_Pages_8-35_20200917.pdf

It may be too large for some email servers to leave as an attached file. If that becomes an issue I can open up my DropBox slice I use for folks to be able to download larger files. The file named about is 18.2Mg or so in size.
 
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1971 Mustang Sportroof M code
In addition to the above, grounds are critical. Make sure the ground cable is connected from the battery to the chassis (bottom screw on the voltage regulator) to the engine, and the grounds are functional (clean).
 

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