# New fan clutch installed, fan runs constantly!



## CK82

I was told my fan clutch was bad on my 95 Chevy, so it was replaced, it now runs constantly. I used to have a overheating problem only with the plow on at highway speeds. This issue is robbing my truck of a lot of power even when it isnt necessary for the fan to be running. My question is, will this new fan clutch loosen up and eventually not run constantly?? Im not sure why a fan clutch would be engaged all the time considering it is a clutch and should engage and disengage when needed!? Please help, I already called my mechanic he said it should loosen up some and "maybe/possibly" run less.

Thanks, Chris


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## bribrius

CK82;488621 said:


> I was told my fan clutch was bad on my 95 Chevy, so it was replaced, it now runs constantly. I used to have a overheating problem only with the plow on at highway speeds. This issue is robbing my truck of a lot of power even when it isnt necessary for the fan to be running. My question is, will this new fan clutch loosen up and eventually not run constantly?? Im not sure why a fan clutch would be engaged all the time considering it is a clutch and should engage and disengage when needed!? Please help, I already called my mechanic he said it should loosen up some and "maybe/possibly" run less.
> 
> Thanks, Chris


mine does too. but i never had mine replaced. i ignore it.


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## streetfrog

With a fan cluthc your fan will rotate constantly regardless. The clutch engages and locks the blade to it so that it spins faster than normal the hotter that it gets. The only time that your fan will not spin is when the motor is off. 
It is a common misconception that the fan will only spin when the clutch engages. 
If you want to lose less HP then get rid of the fan clutch altogether and put a flex fan in or put a 2 speed electric fan in.


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## bribrius

streetfrog;488839 said:


> With a fan cluthc your fan will rotate constantly regardless. The clutch engages and locks the blade to it so that it spins faster than normal the hotter that it gets. The only time that your fan will not spin is when the motor is off.
> It is a common misconception that the fan will only spin when the clutch engages.
> If you want to lose less HP then get rid of the fan clutch altogether and put a flex fan in or put a 2 speed electric fan in.


hey thanks. my fan runs full tilt almost all the time. figured it was broken. maybe it is?


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## CK82

All I know is that, before the fan clutch was replaced, the truck never overheated with the plow off, with the plow on it would get hot at highway speeds and I would have to come to a stop in order for the fan to really kick in! Now it runs constantly (full tilt) and robs the truck of a lot of power, not to mention its super loud and I'm sure the truck will have a hell of a time pulling my trailer this summer. What was the difference between the old fan clutch and the one that was installed, shouldnt they both operate similarly. It wasnt good at all that the truck would get hot with the plow on at highway speeds with the old fan clutch installed, but I would rather have that than what is going on now. On my 06 GMC 2500 u cant hear or feel a difference at any time. Any other suggestions or info would help. I would like to not have to get a whole new setup here considering I just had a new fan clutch installed. There is an auxilary fan in front of the radiator that has been inoperable for awhile now, I guess that can stay that way because there is no way the truck will be overheating at this point.


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## streetfrog

You mat havr gotten a bad fan clutch. It has to have a warranty so just replace it


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## CK82

Ok I will check into it, the problem is I already called the mechanic and he said thats how it will be. I am going to have to watch it and really pay attention closley to see if it is actually engaged all the time. Thanks for any input.


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## ght1098

My truck overheated with the plow on so I bought the HD fan for it and that thing "runs" all of the time. I only use it in the winter with the plow on, change it back to the factory one in the summer.


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## CK82

Do any of you know if you can spin the fan by hand while the truck is off, if the fan clutch is bad? I was told my fan clutch was shot because the fan was able to be spun. ??


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## bersh

CK82;491111 said:


> Do any of you know if you can spin the fan by hand while the truck is off, if the fan clutch is bad? I was told my fan clutch was shot because the fan was able to be spun. ??


You will be able to spin it, but it will take some effort. It shouldn't "free wheel" spin though.


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## ght1098

They will spin pretty easy with the truck off, I doubt your original clutch was bad. As stated earlier, they don't "engage" until they are warm. You probably got the HD fan replacement and that is why it "runs" all of the time.


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## streetfrog

The fan clutch should have resistance when motor is off. Still spin but stop as soon as you let go. I just had to replace mine today. The radiator blew yesterday ( tank split down the middle) So I put that in .
Now my truck is running hotter. My clutch was bad so I put a new one in today ( has resistance when off). I also bought a push/pull 12" electric fan at advance auto parts for $59.95. It will fit nicely in between the Rad. and the fan with 2 inches to spare. I can toggle it on while driving and off for plowing. I would suggest the investment to anyone with a chevy that runs towards the 200+ % mark.
Its made by Hayden. Part number is 3670 for anyone that wants to get one. 
It is thin front to back so fits on the motor side of radiator nicely with room to spare AND is reversable.
Pepboys, autozone and advance auto and VIP all have the same ones.


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## CK82

I have an electric fan already installed in front of my radiator. It currently does not work, and at this point it isnt needed. Like I was saying the new fan clutch has the fan engaged all the time, so I know the truck will not overheat. My chevy never overheated prior to the new fan clutch being installed, EXCEPT when the plow was on, and even yet it only did so at highway (over 45mph) speed. I understand that this new fan clutch may be a HD fan clutch, but regardless it should only be running when necessary. Im sorry to beat a dead horse, but I am looking for more information that I already have here. If indeed the old fan clutch was bad then why wouldnt the truck have overheated in the city (which it never did regardless if the plow was on or off). I just cant get over the idea that my truck is going to be robbed of a lot of power, not to mention be very loud at all times while driving. Thanks for your all your input thus far.

Chris


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## CK82

Should I take my truck back to my mechanic and tell or ask him if he installed an hd fan clutch?? Theres no way this can be a constant issue everytime I use my truck.


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## streetsurfin'

Take it in to your mechanic and let him explain how it works to you and check it over if needed. You don't seem to be grasping what they are telling you here as to how they work; no offense meant. It will always be driven by the motor. It will not stop spinning and does not disengage like a manual transmission's clutch. It uses a viscous fluid that causes it to grab harder at higher temps so the fan is driven faster and allows some slippage at the lower end of the temperature range so it is not driven as fast when not needed. It will always use some horsepower, more when needed, less when not. The clutch does not totally disengage it from action, but will slip a little when maximun cooling is not needed. 

Do you really feel the horsepower being robbed or is it a matter of the noise causing you to think it is? If the old one was shot you would have been used to less noise and what you are hearing now could be considered normal. It was likely barely spinning at the proper speeds before and much quieter, thus the overheating.

If this helps you understand how they work, then taking it back in is not necessary. A HD clutch is a positive in the case of plowing. You are also cooling your transmission and that will help extend it's life.


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## bersh

One thing to keep in mind is that if you are hearing it run fully engaged when you first start the truck, this is normal. I've now owned 7 different GM trucks/suvs, and on every one of them the fan clutch will be engaged when the engine is first started, but will quickly disengage once it warms up a bit. I'm not sure if this is due to the fluid being thicker (thus engaging) when they are cold, or due to the fact that maybe the bimetal spring is shrunk enough that it is engaged, but either way it will be engaged for a short time after you start a cold engine.

I just installed the updated fan clutch on my 2500HD, and the new clutch does engage more often than the old one did for sure. Although it may be affecting my fuel economy a bit, it's a good trade off as the motor and especially the trans now run considerably cooler than before the install. I can now drive around with the plow in any position and not have to worry about the tranny temp getting up near or past 200°, unlike with the original fan clutch where I was borderline cooking the tranny after driving a couple miles, messing around with the plow position the entire time trying to find the sweet spot. Since the install, the warmest my tranny temp has been was about 160°.


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## CK82

Thanks for the posts guys! I have driven the truck a few times since, it does seem to kick on and off more than I thought. I also dont have any problem at all now with it overheating. I know I should look at this as a positive and I do now that I have a better understanding of things. One question though, this will be the 3rd year I have plowed with the truck, the previous owner did some plowing but not commercial. It has just under 128k on the truck, and the tranny went in early December. I am wondering if the constant heating up over 210 and then cooling down ruined the trans, or if maybe it was just its time to go?? Now that the truck stays at a constant 210 or less, I think this should really benefit the trans and the big block 454. Oh one last thing it does have a trans cooler, but I would assume this has to have air flow to properly cool!?

Thanks, Chris


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## KGRlandscapeing

u can tell that alittle fan is robbing ur truck of power i think u need more power


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## tkrepairs

every once in a while my truck will feel like its cutting power. it almost seems computer related like it would cut power due to excessive heat or something like that but i wouldnt be close to overheating either the engine or the tranny. it would kick a couple times on and off like that, is it possible im feeling the fan kicking on and off? only does it with the plow on, at least i only feel it then. doesn't happen a lot but occasionally it throws a fit.


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## streetfrog

Make sure that it has the heavy duty RV trans cooler on it. The regular small one is about 6" by 10-12" and thin. The heavy duty one is about 10"x 12-14" and about 1" thick. That is the kind you want for plowing. That will help keep the trans significantly cooler.


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## B&B

tkrepairs;498835 said:


> every once in a while my truck will feel like its cutting power. it almost seems computer related like it would cut power due to excessive heat or something like that but i wouldnt be close to overheating either the engine or the tranny. it would kick a couple times on and off like that, is it possible im feeling the fan kicking on and off? only does it with the plow on, at least i only feel it then. doesn't happen a lot but occasionally it throws a fit.


 The fan engaging and disengaging is exactly what your feeling tk, it's more noticeable on the 6.0's with a heavy duty or plow prep clutch installed. The fact that you only feel it with the plow on is telling you that the fan clutch is doing it's job correctly


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