My engine temperature gauge in my 91 ranger always fluctuates. It'll say a little above cold one second then normal the next, and its like watching a mini windshield wiper go back and forth. I was wondering if anyone elses does the same, and what might cause it..

 

Well what it sounds like to me is that if your engine is warmed up and the fan comes on then you can watch the temp. go down. Then once the fan goes off the temperture will climb back up. This is normal operation. But if the gauge keeps going back and forth without stopping then that would have me stumped.

 

when was the last time you thought of the thermostat? Check it and see. temp should not fluctuate that much at all. generally the rangers have a continous running belt powered fan so the temp is constant.

 

I agree with josser. Ford OEM thermostats seem to fail early. Fortunatly, they fail in the open position, which results in the engine running a bit cooler than spec, and could account for what you are seeing. The thermostat's purpose is to maintain a constant, efficient temperature.

 

An if the rest of it checks out the thermostat is good etc. you might want to look at the wire connection in your sender, You havent added anything to the dash lately have you . An do the other gauges read normal ? A buddy of mine had a cheviee an a dash bolt backed out, that also grounded his dash . That made his gauges were reading goofey also