I'm stumped on my temp guage. Its in the dash of my 66 f100, and at first I thought it was the regulator behind the dash. I replaced that and it still didn't work, so then I bought a new sensor for the intake manifold and It still doesn't work. Now I googled and ive read that you ground the sensor wire and the guage should sweep. It doesn't, but if you put it on the hot side of the coil it does. Any ideas guys? I like how the factory guages look so my last resort would be replacing the guage. Maybe I missed something
Check your gauge. Get two "C" flashlight batteries end to end and run jumper wires to the posts on the gauge. The needle will move slow but should end up somewhere near hot. With one battery the gauge should be near half. Don't ground that sensor wire too long or you'll smoke your instrument voltage regulator. And yeah, if you ground that wire, if all is well you'll peg the gauge.
Ford gages run backwards, don't they? get a couple resistors, one about 50 ohms and the other about 200 ohms, try each one on the sender connection at the gage (ground one side of the resistor, connect the other side to the gage), see if that makes it move to cool and warm.
Are you sure you have enough coolant in there or no air pockets? The sender won't work if it's not submerged. You should be able to measure the resistance of the sender with an ohm meter. One lead on the housing of the sender, the other where the gauge wire connects. If the resistance changes (not sure of the specs) as the engine heats up, it's the gauge, if not, check the sender.
Stop. Take an ****og voltmeter and check the power wire to the gauge. You should have a moderate pulse of voltage from the instrument voltage regulator (~5v). Ground the sending unit wire TEMPORARILY, gauge should climb to maximum, do not allow gauge to sit at maximum, turn the keyswitch off. If you have the correct sending unit, test the ohm range by heating the engine you should be around 30 ohms at operating temp (approximately). It is highly likely that the gauge has been fried from overvoltage, the gauge should never receive 12 volts. Email us if you need the gauge repaired and calibrated: service@morrisgauge.com
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