| JeffSmith | -- 06-18-2014 @ 10:29 AM |
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I am working on my 29 Hot Rod it has a 42 flatty in it and 49 merc gauges that have gone crazy on me.(they have been in it since the 50’s) 1) My fuel gauge goes past full when starting and stays there, the float is good. 2) The oil pressure stopped working i replaced the sending unit and wire. 3) the temp gauge goes past hot after starting and comes down to hot off and on even thoe it is running cool. I changed some of the wires and both the temp sensors. Any idea’s? shop.1892@hotmail.com
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| supereal | -- 06-18-2014 @ 4:35 PM |
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There is supposed to be a voltage regulator in series with the gauge "hot" side where all gauges are supplied with power that lowers and stabilizes the readings . If just one gauge was off, the diagnosis wpuld be different. The regulator is a Ford part, and necessary. I suspect someone eliminated it in constructing the hot rod, or is is defective, if present.
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| TomO | -- 06-19-2014 @ 9:37 AM |
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Is your hotrod 6 volts or 12 volts? The gauges are set up for 6 volts and if your hotrod is 12 volts, you need a voltage reducer. The fuel gauge will go past full when the wire going to the sending unit is grounded. Your sending unit could be shorted to ground internally or if it is an after-market unit, the incorrect resistance. The Temp gauge reads hot when the circuit to the sending unit is open. I don't know how the gauges would react if they were wired backwards, but it may be a possibility. The sending unit wire for the fuel gauge goes to the driver's side of the gauge and the power goes to the passenger side of the gauge. It is difficult to tell where the other wires connect from the wiring diagram in the shop manual. Tom
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| JeffSmith | -- 06-23-2014 @ 7:22 AM |
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Thanks For the info I did find that there is a ceramic resistor wired in befor the gauges I took it out and put in two 12 vlt reducers one to the temp and onr to the fuel & oil presure and that seemed to work. thanks again for your help.
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| TomO | -- 06-23-2014 @ 8:32 AM |
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I am not a fan of hot rods, but your car makes a good impression. Tom
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