Fan Clutch performance test?

[Tuesdak]

All I can find is a procedure to 'short a wire' and wait 15 min. Maybe that's a "It's Dead, Jim!" Warranty cost control procedure?

Is there a better procedure to test the fan clutch's performance? I have seen 2 min at 2000 RPM to speed up or slow down on GM stuff also a generous warranty procedure.

I am looking at a clutch that won't lock up at idle. However if I go to 1200 RPM it comes up to speed. Watching like 490 fan RPM not ramp up at idle even though the ECM is calling for 99% PWM. 1200 RPM it comes around. I do not know if it's an OEM or aftermarket as the PO said it was replaced sometime in the past.

 

[Tuesdak]

Bump.

 

[cerberusiam]

Short the wire and it will probably be dead. PWM circuits do not like full voltage all the time. If it is calling for 99% and you aren't getting at least 90% of idle speed either it is locking out at a idle or the fan is compromised.

 

[Tuesdak]

Official procedure below. The "Warm up engine first" and "NOTE: It maybe take 15 minutes before fan speed increases" is what's killing me and venting the AC from overpressure. Step 6 is the "short a wire" I refer too. Cold idle it won't lock up. Engine warmed up fine. 1200 RPM cold/hot, locks up fine.

ELECTRONICALLY CONTROLLED VISCOUS DRIVE - DIESEL


You can fabricate a back probe tool from paper clip, wire, alligator clip. or spend big bucks on this miller tool. Make sure the fuse hadn't blownyou should have 12 volts at pin 6 fan connector. Powered by fuse #4 in the TIPM (PDC)



If the fan assembly does not free-wheel and a metallic grinding sound exists, replace the electronically controlled fan drive (Refer to 07 - Cooling/Engine/FAN, Cooling - Removal) .



NOTE: The following test may take up to 15 minutes to perform.

The engine should be at normal operating temperature.

1. Set the parking brake and verify the transmission is in park or neutral.
2. Set air conditioner (if equipped) and blower fan to OFF.
3. Start and allow engine to reach normal operating temperatures.
4. Stop engine, connect the scan tool and select appropriate model year and engine option.
5. Check for and correct existing DTC's
6. Using Tool 6801 , backprobe pin 1 of the electronically controlled viscous fan drive connector, with the harness connected located at the lower fan shroud to battery ground.

NOTE: The fan drive control coil is energized to 12 volts at this time.

WARNING: A spark may occur when connecting pin to ground. Be sure that no combustible material is in the area.


7. Using the scan tool, verify that DTC 0480 set. If it is not set, verify that a good ground is available.
8. Start the engine.
9. Actuate engine speed to 2000 RPM.
10. Go to the SENSOR screen and observe the fan speed.
11. Run the engine at 2000 RPM until the fan speed increases to 1850 RPM or more for 30 seconds.

NOTE: Fan RPM may ramp up slowly.

NOTE: It maybe take 15 minutes before fan speed increases.
12. The fan speed should be in accordance to the table below.
13. If fan speed does not increase, make sure that the jumper wire has a good connection. If so replace the electronically control viscous fan drive.
14. If the fan speed does increase and there is still a concern, refer to the appropriate Engine Electrical Diagnosis Section to diagnosis the electronically controlled viscous fan drive control circuit.



ELECTRONICALLY CONTROLLED VISCOUS FAN DRIVE SPEEDS
ENGINE RPM FAN RPM (Min)
1000 950
1500 1420
2000 1850
2500 2230