Alright, I have swapped my gauges and gotten everything working in my 85 xcab/4wd truck. Swapped in the full gauge setup with speedo, tach, voltmeter, etc. I knew about the oil pressure switch situation so until I had the correct sending unit, I left the wire unplugged. I purchased the oil pressure sending unit from Napa. The new sending unit has the nub on the end where the wire slides on, but it has a small tab on the side as well where something else should attach. I get nothing when hooking up the wire to either of these connectors on the sending unit. Is there another wire that should go to the extra connector? Or what gives? Is my oil pressure gauge bad? I would think that an oil pressure sending unit would need some sort of power as it is not mechanical so should there be a power lead going to the extra connector?
Truck gauge swap woes
Jan 16, 2004
2 Replies
Usually the sender is just a variable resistance, grounded by the case, one lead to the gauge with then is supplied by a regulated voltage; so many volts/so many ohms = so many miliamps and that'w what the pressure guage reads, its nothing more than a small current meter calibrated to read out oil pressure.
Check the paperwork with the sending unit. It might be a ground-wire connection, for cars where the switch doesn't ground through the threads properly.
If it's another insulated terminal, some cars have a dual sender that has both a gauge sender and an idiot-light switch built in - the advantage being the idiot light means "Hey, Dummy! Look at the gauges! You have a problem!" ;-P
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