Expert: Roland Finston - 8/19/2011

Question
1989 Dynasty 3.0 liter 6 cyl :
engine temp gauge stays up just a bit above 2/3 index mark . My recollection was that it used to be no more than halfway up gauge. I feel it is way too hot.

Replaced thermostat( twice last week), new temp sending unit to dash gauge , and new temperature sensor to computer for open/closed loop. Currently in the 90 degree summer , driving w/o thermostat and observed that engine temp reaches halfway index, guess it  then goes into closed loop. Plan to add thermostat in cooler weather.

Radiator fan appears to turn on only with A/C on .
I no longer see fan running after I turn off hot engine the way it used to run immediately after shutdown.
Radiator Fan relay switch mounted on driver fender appears functional via ohm out and feel /hear it click on/off.

Suspect an issue with turning on radiator fan .
Lower radiator hose does not ever feel very hot/warm.
Upper hose gets hot.
Believe water pump working as coolant flows w/o radiator cap , goes into overflow reservoir
Radiator replaced 2 years ago.

Suspect that fan relay may not be receiving input signal from ( ?? ) .

Answer
My observations:
The normal temp gauge range is 1/4-3/4 and it will run hotter in the summer than you may remember. I would not get too concerned unless you get frank overflow and near H readings, particularly absent a fan response. When you remove the plug on the coolant temp sensor (the two-wire plug that goes to the pcm, not the one for the gauge) that should provoke the fans to come 'on'. That would verify the circuit.
I don't believe the fans will run, normally, after you turn off the engine because the ignition 'off' takes away the 12v necessary to activate the fan relay.
Open/closed loop has no affect on the fan action, it is only activated by the coolant temp or the 'call' for AC. Fan normally won't come on until gauge is about 5/8.
It all sounds pretty normal to me at this point.
Roland