Running hot, high A/C pressure

[runderwo]

My truck runs great and blows cold air until it gets over 95-100 degrees out.

When it is that hot out, when it is warmed up, the A/C starts blowing warm at idle and the high side A/C pressure goes to 350 (can be brought down to 200 by spraying the condenser with a hose) and also at idle I see the engine temp needle creep up to about 3/4, still in safe area though. If I get on the highway the A/C starts blowing cold again and the temp goes down to the normal 1/2 position.

I would suspect that the fan is not keeping up. But the clutch seems nice and tight when I try to spin the fan. Should I try removing the clutch and connecting the fan directly with a spacer to see if this brings the temp/pressure down? Then I would know that I need a better clutch. Also, what are the chances that the plastic fan blades are flexing. Any other ideas?

 

[Anime]

The fan clutch may be stuck, possibly even seized, so instead of the temperature-controlled engagement, it's simply going full blast, which overloads the engine instead of providing cooling as needed.

There may also be other issues with the A/C, such as slightly low refrigerant, a low side pressure switch malfunction, etc.

The fan blades being plastic isn't a problem, though the stock fans do seem to become brittle with age and eventually crack. An inexpensive aftermarket replacement is available if you discover the stock fan blades developing cracks around the center.

 

[runderwo]

Pressure switch is good, I checked it by halfway discharging it, thumbing the throttle and watching the A/C clutch cut out reliably whenever the low side drops below 25. Also, the low side stays around 35 even when the high side is going thermonuclear, so it doesn't seem like a low charge or any kind of internal obstruction.

What is the best test procedure for the Explorer fan clutch? What's the difference between the "standard" and the "heavy duty" fan clutch for the A/T models?

 

[runderwo]

Aha, I found this post. Looks like there was an improved version of the fan after the 91 model year:
https://www.explorerforum.com/forums/showthread.php?t=159173

 

[Anime]

The 10 and 11 blade fans weren't an improvement, they were simply designed to move more air on the automatic transmission models, along with the heavy duty clutch. Those with 10 blade fans have used the 9 blade aftermarket replacement and found little difference.

Usually you test the fan clutch by making sure it spins freely with the engine cold, before starting, then check again with the engine off after it has been driven at operating temp for some time, and the clutch should have at least some resistance. If it spins freely, and the engine temps are higher than normal, it's the clutch.

The standard clutch is usually found on manual transmisson models, and has a lower degree of thermostatic engagement. The heavy duty clutch came in the models with automatic transmissions and has a higher degree of thermostatic engagement, moving more air. The cooling systems of the standard and automatic transmission models also used different single/dual core radiators.

 

[runderwo]

Here's basically how I checked it. Cold, if I spin it, there is enough resistance to stop it after freewheeling about a half turn. Hot, there isn't exactly what I would say "resistance" there, since I can turn it easily without much force, but it doesn't freewheel at all either.