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I have a Class C motorhome that has a 1989 Ford E350 7.5 640 engine. I noticed that the temperature guage needle wasn’t moving (continuously pointing to Cold). I located the sensor to the right of the distributor on the top of the engine and checked for voltage in the harness with the key on run. The only voltage I got was 0.02 V. So I’m assuming there is a break in the wire or something wrong at the guage. I’m not sure where to go from here. Any help would be greatly appreciated! (The wife’s starting to tap her foot, so times running out.)
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check all fuses. ground the sensor wire then turn the key on to see if the needle goes to hot.
If so replace the sensor. if it does not move you will need to trace the wires to the gauge and
ohm them. If the gauge does move do not leave the gauge needle like this. just long enough
to see the needle move. 🙂The harness has two wires, black and green. I grounded out the black wire and turned the ignition to “run” but the gauge’s needle didn’t move. I checked the fuses under the driver side dash and all were good. I don’t have an owner’s manual for the motor-home so I don’t know what systems these fuses protect. I also searched for a fuse block in the engine compartment but couldn’t find any. I tried following the wires from the harness. They enter a taped bundle of wires running on top of the engine alongside the fuel injectors. I expected to see them separate from the bundle and head to the instrument panel, but they didn’t. This is leading me to wonder if I don’t have the wrong sensor. I thought of tracing the wires from the instrument panel but this seems quite involved. I don’t want to pull the instrument panel out if I don’t have to.
College Man, could you explain how to ohm the wires at the gauge and what resistance I should expect. Thanks again for your help.usually the temp gauge is a one wire connector. sounds like the two wire sensor
may be the ect engine coolant temp to tell the computer how warm the engine is
to adjust fuel trim.Yes, you’re right. I pulled a wiring diagram form “Shop Key” which showed a red/white wire going from the gauge to the sensor. But I’ve searched high and low for the sensor and couldn’t find it. Any idea where it might be?
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