Testing a fan clutch?

[The motor guy]

The shop thinks I need a new fan clutch because it wasn't speeding up and slowing down. It was 55 degrees outside that morning and I said it's probably not going to since it's not hot outside. I read on the internet that you can spin it by hand and if it stops almost immediately it was okay. Then I have another guy saying its bad because it continues to speed for like 5 seconds after I shut the engine down. Later that day when it was warmer outside and it was increasing and decreasing in speed like it always has.

 

[jeepman3071]

You have to test it at operating temp. Get the engine to operating temp, shut it off, try spinning the clutch by hand and it should have a bit of resistance.

 

[DoubleWasp]

On your Cummins? They're tough to gauge. Due to them being electronic, they do what they want when they want. Idling a diesel looking for the fan clutch to turn on is even tougher because they're not big heat shedders when not under load. However, they can definitely under perform without giving any noticeable signs. I had no codes, no overheating, and no other noticeable symptoms other than occasionally crawling to 208, and failing to engage when my AC pressures got too high. Did perfect otherwise. Bad fan clutch. When not engaged by the computer, it's going to act completely loosey goosey.

 

[camrydriver111]

Quote:

Later that day when it was warmer outside and it was increasing and decreasing in speed like it always has.

Your clutch fan is probably fine then. I think listening to it while driving is the best way to test it. Spinning the fan by hand doesn't tell you much.

 

[JMJNet]

May want to check with the Cummins forum/crowd? This is more of a generic forum, not that there are not any Cummins experts/owners here but who knows.

 

[Chris142]

Those electric fan clutches on those Dodge trucks are junk! We replace them on almost every 07+ Dodge truck with a 6.7 we get in the shop. They have a huge failure rate.

 

[The motor guy]

Originally Posted By: camrydriver111

Quote:

Later that day when it was warmer outside and it was increasing and decreasing in speed like it always has.

Your clutch fan is probably fine then. I think listening to it while driving is the best way to test it. Spinning the fan by hand doesn't tell you much.

Of course I checked it today and it was just idling, not speeding up and slowing down. Outside temp was 75

 

[JHZR2]

Isn't there some trick to test with a roll of newspaper?

 

[The motor guy]

Originally Posted By: jeepman3071

You have to test it at operating temp. Get the engine to operating temp, shut it off, try spinning the clutch by hand and it should have a bit of resistance.

It has resistance moving it by hand. If you shut the engine off it continues to spin, not sure if that means it shot also.

 

[mk378]

The electric type will disengage when you turn the key off, because, well, it's electric.

 

[Chris142]

Originally Posted By: JHZR2

Isn't there some trick to test with a roll of newspaper?

not his electric one.

 

[The motor guy]

Originally Posted By: camrydriver111

Quote:

Later that day when it was warmer outside and it was increasing and decreasing in speed like it always has.

Your clutch fan is probably fine then. I think listening to it while driving is the best way to test it. Spinning the fan by hand doesn't tell you much.

The guy at the shop thought it was bad because the ac pressure went to 400psi and he said the fan should have spun up because of that. Last I checked the fan really doesn't do much this time of year when it's only 65-75 degrees outside, usually I only hear the fan during during summer months. I've had this truck for 10 years now, so I would know. Just three weeks ago I remember it blowing the dirt off the ground when I was backing up 75 feet at 10mph with the trailer behind me. lol

 

[Colt45ws]

Originally Posted By: Chris142

Originally Posted By: JHZR2

Isn't there some trick to test with a roll of newspaper?

not his electric one.

If you had a way of interrogating the computer and seeing when it called for it to be locked and then test and see that its actually locked? Would that work?

 

[DoubleWasp]

Originally Posted By: motor_oil_madman

Originally Posted By: camrydriver111

Quote:

Later that day when it was warmer outside and it was increasing and decreasing in speed like it always has.

Your clutch fan is probably fine then. I think listening to it while driving is the best way to test it. Spinning the fan by hand doesn't tell you much.

The guy at the shop thought it was bad because the ac pressure went to 400psi and he said the fan should have spun up because of that. Last I checked the fan really doesn't do much this time of year when it's only 65-75 degrees outside, usually I only hear the fan during during summer months. I've had this truck for 10 years now, so I would know. Just three weeks ago I remember it blowing the dirt off the ground when I was backing up 75 feet at 10mph with the trailer behind me. lol

Oh yeah. Typical. You better do something about that, or you'll start shooting AC system seals and hoses soon.

 

[The motor guy]

Typical of a fan clutch? Or something else?

 

[Colt45ws]

Some kind of lack of airflow. Either something blocking airflow through the radiator and condenser or there isnt enough airflow in the first place. If its 75 outside the head pressure should be like half that.

 

[DoubleWasp]

My truck did the same thing before so replaced the fan clutch. It's supposed to ramp up when the head pressure hits 260. It would just let it hit the compressor cut out at 450

 

[The motor guy]

It was like 60 out when it did that.

 

[The motor guy]

According to the tech it shouldn't have mattered that it was only like 55 degrees outside it should have done it regardless. I guess he was right.

 

[The motor guy]

So how is anyone supposed to know something is wrong unless they happen to have the ac hooked up to gauges? My truck hasn't thrown any codes or anything. The ac blows nice and cold.