Ok it must be getting warm out and I know there have been many threads on the issue, but in my search I haven't found an answer.

Let my start with the description on the problem that recently popped up while I was vacation last week in Southern Utah. I towed my trailer from Socal to Utah and everything was fine. The did what it was supposed to and kick in around 208° and turn on full at 219 to 220° ECT. It would drop the temps down to around 200 and disengage. So all is good right. Now while driving around going to different sights without the trailer the clutch would engage to about 50% and not disengage until the ECT would drop to the low 180's.

Now the next morning when i first started the truck the when was total disengaged and spinning under a 150 RPM even with the AC on max. If I waited before driving the fsn speed would drop below 100 RPM. Once I drove for a bit the fan would act normal at idle.

This problem doesn't seem to effect when I am towing.towing.I come home it cooled fine. The only cooling exception was coming south on the I15 out of Primm NV climbing Mountain Pass. It is a 10 mile 6% grade with about 105° air temp. The truck got upto 225° ECT but the fan was roaring the whole. Once I crested the top to temp came down quickly.

So the question is what is up with the fan clutch?

 

That sounds pretty normal. When you are running the AC the high pressure switch can activate the cooling fan, regardless of coolant temp. I haven't found a way to monitor the high pressure switch thru the Scangauge or ForScan.

Typically the switch will engage when you are idling or at very low speeds with little air going across the condenser. What I've observed is at idle at a stoplight the HP switch will engage the clutch 100% (850-900rpm). When you first take off you'll hear the fan whir for a second while the clutch disengages. It will then try to hold 1200-1400rpm until the AC pressure drops which for me is usually around 40mph. Next stop the cycle will start over. This is driving in 100+ ambient temps. Lower temps it doesn't seem to make the HP switch as quickly and the fan won't lock up at stoplights. Thru all of this the ECT is usually 190-192. The extra fan speed keeps the motor basically on the thermostat.

Regarding your 224F ECT I see that on the long grades too when the temp is over 100F if I'm pushing the truck hard. So long as the fan is roaring it's working correctly. You can monitor the FSS which should be slightly higher than engine RPM. I pull my long hill around 2700rpm and I see ~3100rpm fan speed. My previous 05 truck had a bad clutch which would engage the fan for about 10-seconds and then it would cut out for 5-seconds before the fan would re-engage. That got the truck hot quick and I had to slow down to keep the temps in check. My current 06 holds itself on 100% the whole way. Were you watching oil temps on that climb? At 224ECT I'm seeing almost 240EOT which isn't recommended. It will start defueling at 253...

 

Here are some screen shots

This is at idle with the AC off.

This is with the AC on

So with checking my FSS it was the same at idle whether the PCM command 0% or 100%.

The head scratcher is the fan clutch seems to work normal while driving for the most part.