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The first link only deals with thermal clutches, which we don't have.
Not exactly. You just replace the "obsolete thermal spring" with a electronically controlled solenoid valve and add a RPM sensor. Rest of the clutch is the same. It's like asking how a gas engine works and calling out the difference of a TBI injection system vs. the carburetor equipped one I posted.
BTW the first link at the bottom of the page has EV clutches and the 2nd link PDF is how Spring Thermal Viscus clutches work.
In Summery the Electronic - Viscous, EV, Fan Clutch is merely an update to the old technology. It (can) suffers the same 'morning sickness', running after first startup, that all viscus fan drives suffer from.
Aside of doubling the price for a fan clutch and giving you more things to go wrong it has some real advantages the least being it can tell you when things go wrong.
Problem we have with cooling systems is when you go from light/no load to full power full load on a grade. Say it's a good long grade with a heavy trailer. Thermostat is closed, radiator is cold, and you just dropped the go pedal to Chernobyl full nuclear. Start the timer on ECT runaway until the fan gets on to stabilize the ECT. First the coolant has to heat up enough to start opening the thermostat. Add some temperature overshoot as the thermostat slowly opens up. Now you get some cooling as the radiator gets heatsoaked. Now you have a heat soaked radiator, t-Stat full open and what about the fan?
The Obsolete Spring Thermal fan clutch's thermal spring is just now seeing the hot air to warm up the spring and then a delay as the working fluid gets to the working chamber. Add a long ECT runaway delay time here before the fan gets up to speed. It can take 2 min to get the fan on per the allowed time delay from the EV ones before a code trips.
With the EV fan clutch the computer can start the fan coming on before the radiator is even hot. So when the hot coolant hits the radiator the fan is just starting to come on and further ECT rise is slowed or stopped. In other words it eliminates the spring heat up delay to bring on the fan and stops ECT runaway sooner during the grade climb because the ECM starts the process to get the fan running full speed before the radiator is hot.
This is great for AC systems as your condenser can get hot and the compressor tripping off before the engine warms up. The cold engine radiator actually cools down the hot air coming off the condenser so the thermal spring never sees the hot air and allows the AC system to overheat. EV systems will kick on the fan just for AC cooling - Worth every penny of the $500.00 wire munching EV clutch when it's 120 degrees outside and the AC starts and keeps blowing ice cold without stopping to wait for engine warm up. (Note early EV programming allowed AC systems to overheat and was fixed per a TSB flash update.)
" i have my Touch set on fan rpms, will this be 'actual' speed? As clutch wears, will this be commanded speed or 'real' speed? And what is min/max RPMs?"
Computer commands a % of lockup looking for a desired RPM range biased off engine RPM. The computer does not command a specific RPM - just a duty cycle for the solenoid aka % on. You may be able to see desired RPM from a scan tool, etc. Fan RPM should be actual RPM of the fan. Some (most) fan pulleys are driven faster than the engine RPM due to different size fan and crankshaft pulleys. The computer allows like 2 min for the fan to be within a percentage of the desired RPM before setting a code. This includes time to get over 'morning sickness' and slow down as overspeed of the fan also will set a code. More RPM means faster lockup/unlock due to moving the working fluid in the clutch.
If you have an old clutch the ECM just commands more % on time till the fan is within the desired RPM range. Think of a servo feedback loop. The day you need more cooling and the fan doesn't come up to minimum speed in the long time window you get the code.
Max RPM of the fan varies especially with MPH (ram air) and the ability of the drive belt not to slip at full lockup. Sitting still at 100% lockup and 3000 RPM is different max fan RPM than going down the road at 65 with full lockup.
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