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1969 Mark III Gauge Issues

Hello Bill,
You have answered questions for me before and I greatly appreciate your help and advice. I have a 1969 Mark lll with 43,000 miles on it. I have the original window sticker, warranty card and upholstery card. It’s all original. My question today is, my gauges. My gas gauge and temperature reads erratically. Sometimes the fuel will read correctly but will go “low’ very soon after car is running. I did have the sending unit rebuilt a few years ago. The temp gauge runs a little high. Any suggestions?
Thanks again,
Greetings Marv –
The diagnosing of the gauge circuits for your Mark is shown at length in your shop manual. If my information is correct you have already purchased this manual from us at Lincoln Land. If you cannot do the diagnosis as shown in the manual to pinpoint the issues I can give you a list of possibilities. The engine temp., oil pressure and fuel gauge circuits all receive power and operate from a unit known as the Instrument Voltage Regulator (IVR). They are known to go faulty if all gauges seem erratic or out of specification. The other gauges separately could have faulty sending units, bad dash units or bad connections at any location etc. The temp. gauge could be reading a little high because the engine coolant temperature is actually a little high. The possibility of a combination of the above could also exist. Again, the gauge diagnosis is well explained in the shop manual. Guessing and changing parts without some diagnosis can be expensive and frustrating. Have you checked your shop manual for that section? Let us know what you find out.

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