Thermostat and gauge question.

[Grunizzle]

I have a 1991 4.0l ranger

I just put in a third thermostat since I bought it. The previous 2 seemed to cold and the last one I think got stuck open or wouldn't close all the way. Anyway I put in my new one today and when I go test it out on the road, it warmed up to where the needle went right in the middle of "normal" on the gauge then went down and it hovers around the "n" of normal now.

Is this normal? This is pretty much what the previous 2 have done. I don't think I would get sold 3 different brands of broken thermostats. Is it my gauge? I bought a mechanical equis water temp. gauge to install but I could not figure out where to screw the probe in at on the engine.

 

[nitrofan1]

Pardon the pun but that's "Normal". My 94 does the exact same thing, even when it's 100 outside and I'm running the A/C. If you want to verify this go get a Motorcraft (not aftermarket) temp switch. They run around $20 and any odd readings should go away.

I state Motorcraft because I work in auto parts. Standard, BWD etc... just don't seem to get it for me personally when I need switches for my baby. I used those other 2 before especially on the oil pressure switch and they didn't read right. Went with Motorcraft and it worked perfect.

 

[mge_1]

If the Motorcraft Temp Switch the same as Coolant Temp Sensor or is it different?

 

[Big Jim M]

There's two of them!

If the Motorcraft Temp Switch the same as Coolant Temp Sensor or is it different?

The temp switch sends a signal to the computer to tell it the temp is high enough for the computer to use full timing and full lean mixture as needed.
It has no variation.. it either doesn't send a signal or it "switches" and sends the same signal all the time.
The temp sensor tells the gauge what the needle should do. It is variable in it's signal so the proper temperature can be read.
The two senders have different lectric plugs and shouldn't be interchanged.
Big JIm

 

[mge_1]

Thanks Big Jim M. In my case (95 B4000), the temp is also going up and down. Which part to replace first?

 

[Big Jim M]

Thanks Big Jim M. In my case (95 B4000), the temp is also going up and down. Which part to replace first?

No reason to change the switch. It should have nothing to do with the gauge reading up and down. If only the gauge is going up and down and not the actual temperature of the coolant then the temp sender for the gauge could be the problem.
Big JIm