When I start my Ranger the coolant temp gauge needle moves the the normal area. Then after a few minutes it drops below the "C". The engine seems to be OK and there is plenty of coolant. Any ideas?

 

My first guess would be your thermostate is stuck.

 

Back on July 30th I asked for help on a problem that sounds a little like this except on a used F150 Lightning I bought. In my case the guage goes high for a short time then drops back to the low normal range after starting the engine.

First noticed this when the engine was cold, so I replaced the thermostate thinking it was sticking. Did not fix the problem and then noticed that it did the same thing if started hot. By the way, the engine shows no evidence of ever actually running hot.

Got no response from this forum, however, on one of the other internet truck sites at this point a long time Ford mechanic agreed with me that it must be the sensor. Replaced the sensor with no improvement. Another Ford mechanic on that forum said he had seen these types of problems before and it was more likely an internal ground in the guage itself. Have not had time to check the guage out yet, but he said variations of what I have often are caused by a faulty guage.

Charla

 

I know with my 82 Van that all the gauges get their voltage regulated by a IVR (Instrument Voltage Regulator) located on the back of the cluster. My gauges would read low because the IVR was supposed to provide about 5 volts to the gauges and wasn't. I have gotten three different IVRs and each causes the gauges to read different. A friend of mine who works for Ford told me that during assembly they would adjust the IVR to get the gauges in spec. However, if you look at the IVR it is a bimetalic reed switch which opens and closes when the windings get hot. Over time this switch will go bad and lose its regulation. With this IVR when you turn the key on the gauges will initially read high because 12 volts will be going through and then "settle down" when the IVR starts working providing around 5 volts. I found that just a 1 volt swing in the IVR will cause a major change in nthe gauges. You can adjust the IVR since there is a little screw on the unit that when you turn it clockwise you increase the voltage CCW you decrease. I adjusted mine by pulling the cluster out and while leaving it connected and the engine running turjned the screw to where the gauges read perfect. Fill your gas tank and use the fuel gauge as your "meter", adjust your fule gauge to where it just reads full. I don't think ford has replaced the IVR in any analog situations yet, so my guess is that the IVR might just be your problem.