I have a single cooling fan sytem.the fan usually starts at 222 oF.It still works, but its activated around 235 oF and shuts of at around 222 oF. thermostat opeons around 198 oF.what could my problem be?(besides ingnorance)

 

A single fan system does not use the ECM, only a fan switch in the block that grounds and energizes the fan relay. They typically are around 238 degrees. If it has changed somewhat suspect coolant condition or perhaps the fan switch is getting corroded causing poor thermal transfer. Probably not a bad idea if the system has not been serviced to do that and replace the fan switch. NAPA has a couple different ones for lower fan turn on temp and they are much cheaper than say, the JET switch. If you service the cooling system don't forget a new rad cap.