Fuel gage testing
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Fuel gage testing
The fuel gage on my '78 F-250 recently went to "0" and stayed there. I disconnected the connector to the sending unit and checked voltage to ground. The voltage oscillated from "0" to a value (too fast for my multimeter to read the value). The resistance in the sending unit measured 75 ohms so the sending unit and it's ground are apparently OK. I plan to ground the upstream side of the sending unit connector to check the gage later today. But what is the purpose of the oscillating voltage, where and what is the instrument cluster voltage regulator and why oscillate the voltage when the rheostat in the sending unit should do the measuring job?
Hotshot
Joined: Apr 2009
Posts: 14,333
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From: Stanley, VA
The gauge and wiring are easy to check. At the sending unit disconect the wire that goes from the sender to the gauge and ground it. Turn the ignition to "on" and watch the gauge. If everything is okay the gauge will swing all the way to "full". If it doesn't move then there is a problem in the wiring, the gauge itself or the IPVR (instrument panel voltage regulator).
If your temp gauge is working then the IPVR is okay.
The IPVR output is I believe around 5.5 volts and it's a modulated voltage. It's a small box attached to the back of the instrument cluster by one screw and the connector looks like a connection for a 9V battery.
Here' what they look like.
If your temp gauge is working then the IPVR is okay.
The IPVR output is I believe around 5.5 volts and it's a modulated voltage. It's a small box attached to the back of the instrument cluster by one screw and the connector looks like a connection for a 9V battery.
Here' what they look like.
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