99 Ranger temp gauge doesnt work Help!

[patterson302]

I just bought a 99 ranger 4.0 5 speed and the temp gauge doesnt work at all.Its way down past where it should be It doesnt move at all.what should i do.If I cant fix it is there a way to hook up a aftermaket temp gauge.Any response would be appreciated.

 

[Harris]

Easy there big fella...

First off, these engines are pretty good about staying cool. Mine has always stayed around the N in NORMAL unless something bad happens, like a water pump going out. When you turn the key on does the needle move any? When the key is off the needle will sit down all the way to the left. If the needle moves any at all it means the gauge itself is probably fine.

If it does move, indicating the gauge itself is working, you need to check the sensor (also known as a thermometer) by blocking any air passing through the radiator. You can do this with cardboard or anything that will stop the air from being pulled through by the fan. Once you get the air blocked, let the truck run and watch the gauge. It may take a while for everything to heat up enough to move the gauge so be patient. I would seriously give it at least fifteen minutes to warm up fully.

If it still doesn't move the needle on the gauge we'll discuss changing the gauge and, if that doesn't do it, changing the sensor.

 

[Earl43P]

The engine coolant temp sensor can be checked with an ohmmeter. 16 ohms for hot, 275 ohms cold. Take that with a grain of salt, because whatever temperature YOUR sensor is seeing will fall somewhere in between those two values.

If your gauge doesn't move at all, I'd replace the sender and go from there. You want to replace the temp sensor with the RD/WH and BK/WH wires, not the one with the GY/RD and LG/RD wires.

You can do a test of the wiring by jumpering the sensor's RD/WH and BK/WH wires together for just a second while someone watches the temp gauge jump to full Hot. Just touch them together long enough to see the needle move toward Hot, don't leave it like that for long (16 ohms vs. 0 ohms) or you may fry your gauge or blow a fuse (#11).

If you have no help, jumper the two wires then turn the key to RUN just long enough to see the needle move toward Hot, then turn the key back off.