Fan Roar

[JimG96]

Good evening,

I have a new-to-me 2006 2500 Mega Cab 4x4 with a 5.9. It had a leaking A/C system due to a bad compressor. During the diagnosis the shop said it also had a bad fan clutch (likely causing an overheat condition on the A/C damaging the compressor).

Long story short, the truck has a new compressor and fan clutch (and I have a lighter wallet).

The repair was completed 2 months ago and the A/C seem to be working great now, but....the fan is almost always running. It roars as I accelerate and seems to have very little power. It seems the fan finally disengages if I reach consistent highway speeds. I haven't had it long enough to say if the fuel economy is effected by this or not.

I'm not even sure where to start diagnosis on this, but would really prefer to solve it myself rather than not having the truck for a few days while the shop look further into it.

I can't believe this is normal, but have read the fan will engage when the A/C is on. Perhaps it would, but not at the speeds I'm getting.


Ideas I've come up with:

1. Bad sensor - it seems the ECM monitors several systems to control the fan clutch (coolant temp, AC pressure, etc...) - what sensors need to be tested and how is this done?

2. Bad fan clutch - seems the aftermarket ones are prone to being bad. Any way to diagnose this short of changing it out?

3. Thermostat - don't think this is the culprit as the truck doesn't overheat and it didn't do roar before the new fan clutch (but it may have not been working and never engaged either?). That said, I wasn't in a hurry to fix the AC until Houston started warming up.

Any other ideas on where to look / start?

Thank you for any input!

 

[Brian Verberne]

I have the same problem with the roaring. I started when I replaced my clutch fan years ago. I have the 6.4 Hemi 2500, 2016. I have noticed that I do not have the roaring when the air conditioner is not on. It is most noticeable at higher rpms (when accelerating). I´m not sure what to do.

 

[Mister Luck]

Most fan clutches are thermostatically controlled by an internal viscus silicone
sometimes they are referred to as such.

There are kits available to refurbish the clutch with an injection of the silicone solution but sometimes it does not help and the unit needs to be replaced with a new one.

Upon start up you should see the fans blades turn at a slower speed then after warm up after about 10 to 20 minutes of operation depending on the ambient temperature their rotational speed should about double.

If you own a smart phone you may be able to download an RPM speed (tachometer) app it uses the phones camera and light to calculate rotational speed

Metal fan blades are louder than composite probably because of their degree of pitch.

 

[pacofortacos]

Clutch fans should spin faster and not slip much on cold startup (hear roar) - then start to slip (become quiet) after 1-2 minutes max unless it is a very hot day or hot soak engine restart.

Unless the diesel clutch fans are different that gas engines, you shouldn't hear any roar other than on cold start and when it engages when the temp reaches it's designed temp.

In my experience, most aftermarket clutches do not work properly.

you could always get a good used OEM unit try car-part.com

 

[JimG96]

Spot on - replaced the Dorman with Mopar, problem solved.

 

[Brian Verberne]

I have the same problem with the roaring. I started when I replaced my clutch fan years ago. I have the 6.4 Hemi 2500, 2016. I have noticed that I do not have the roaring when the air conditioner is not on. It is most noticeable at higher rpms (when accelerating). I´m not sure what to do.

I had the clutch fan replace on my truck last week. I had to go with an aftermarket product, due to the OEM parts being backordered. The replacement part seems to have eleminated the fan noise.