A quick question on fan actuators.....

[Andyrv6av8r]

I have been doing some research through the TM's and online about how the fan clutch actuator is supposed to work on the 923 but haven't been able to find a satisfactory answer to MY scenario. I have two 923's. On both trucks I can spin the fans without the trucks running and feel the clutches working. Upon starting both trucks, the fans turn. Truck A driving down the Interstate on a hot day, engine temps at 190 degrees, all is well. Truck B driving down the Interstate at 190, I hear the fan kicking in for about 45 seconds, then off for a few minutes. Then on; then off. I can even FEEL the fan kicking in under the load as the engine drops a few RPM's. I never see the temp hand move at all from 190.
Both trucks are good on coolant and all belts are new/tight.
So which truck is working like it is supposed to? Is the fan actuator supposed to engage the fan at full rpm for maximum cooling then " turn off " once the temp drops? One suggestion from a friend is the fan should only kick in " at idle, at high temps " since I should get plenty of cooling air at highway speeds. That makes perfect since and I agree but I honestly don't know. And what is the purpose of the actuator when you have a clutch on the fan to begin with? I'm old school and remember when lots of cars and trucks had clutches on the fan to allow slippage at high speeds yet proper rpm's and cooling at low speeds. Heck I'm old enough to remember " Flex Fans ".

 

[Andyrv6av8r]

Bump for another chance at an answer...

 

[Suprman]

Both of my A2 fans kick on around 200 it doesnt take long with the hugh radiator and big fan to get the temp down so the fan only stays on for a minute or so. Im pretty sure the fan is either engaged or not engaged depending on temp im not sure about slipping at high rpms. High rpms in a car are much higher than the 2100 or so high rpms that the diesel engine makes.

 

[Scarecrow1]

I. Am bringing this subject back to the table in hope someone will add a little more light to it. My 923 a1 has never made any noise coming on and I never heart shut off. I did have an air leak on mine and replaced it today . It did as the other one did just not leak air from it when I shut it off. from what Andy has told me his will come on while heis driving and will drop his RPM,s while doing so so please if anyone knows why this is hopping please add your comments so we can find an answer...........

 

[Stein12501]

Andy my 923A1 runs about 200 deg. and the fan will cycle in and out depending on water temp. The temp control is located in the thermostat housing in the NHC-250. I think they are factory set for 190 deg. to come on not sure what the differential is. Here is an excellent thread that had a lot of info. http://www.steelsoldiers.com/showthread.php?108537-M931-Leaking-fan-clutch

 

[randygk]

Also having cooling issue with the M923A1. It's always run at 180 for the few times we drive it. Took it to a 4th of July parade about 2500 feet uphill and 98 degrees. The temp started to climb and I never did hear the fan come on. It got a little over 200 then we started to level off and slow down so the temp came down. I pulled the actuator and put the sense bulb in boiling water, it opened but didn't seem consistent. The actuator is normally closed and at 190 degrees (stamped on the side) opens and allows air press to the clutch. I put air to my clutch to check for operation and any leaks and it seems fine. I am going to run test by hooking up some some hoses and valve in the cab and bypass the actuator just to manually cycle the fan when driving. I assume it makes a lot of noise, but at my age I could be missing it. I also always wear ear plugs when driving the MV's.

 

[Andyrv6av8r]

Andy my 923A1 runs about 200 deg. and the fan will cycle in and out depending on water temp. The temp control is located in the thermostat housing in the NHC-250. I think they are factory set for 190 deg. to come on not sure what the differential is. Here is an excellent thread that had a lot of info. http://www.steelsoldiers.com/showthread.php?108537-M931-Leaking-fan-clutch

So does yours cycle on and off at highway speeds? How about extended idle periods? Scarecrow told me that he thought his was coming on and staying on.

 

[randygk]

Put air to the clutch while idling and could see the fan speed up, did it at 1500 rpm and you really hear it. Hard to think I would miss it running even at highway speed. New actuator on order.

 

[Stein12501]

Randygk I had bought a M105 trailer and brought it home. It was warm outside and the engine temp was right around 200 deg. Got home and lifted the hood and as I did the fan kicked in and the engine temp dropped right down. Never overheated and I never heard the fan engage. Carlo installed the 2 lock bolts that lock the fan in all of the time and said it made a big difference on engine temp. They made the actuator valve for different temps but I don't know if anyone stocks them.

 

[randygk]

Just ordered it from Memphis. They said theirs was rated at 195 so we'll see. It's possible the fan may have come on at something over 205-210 if I waited, but who knows how old this thing is and for around $150 I'd rather be sure about it. Many dealers carry it and price varies a lot.

 

[Andyrv6av8r]

I just did a test on Truck A, the one that I have never heard the fan operate on. I disconnected the air to the fan clutch and applied shop air with the motor running at 1700 rpm's. The fan kicked on with a definite rpm drop. And the fan noise was unmistakable as I cycled it on and off several times. At nleast I know that my clutch is good. I'll check the fan actuator next one day soon.