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Author Topic: Chevy 454 Fan Clutch. How often does it run?  (Read 2314 times)


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Chevy 454 Fan Clutch. How often does it run?
« on: August 10, 2016, 03:36:39 PM »
Our 94 Coachmen Santara with the Chevy 454 motor had some overheating heating problems in our last trip thru W Virginia.
On long uphills the temp gauge would get close the the red marks.. We turned off the ac and turned on the heater to help dissipate the heat.

 What is odd is that our fan clutch did not come on.. It has been sporadic when it would turn on/off.   I have seen it come on at 170* and other times it would not come on at 240*

So I decided to replace it..   The oem chevy dealer wanted $300 for one..  Ouch..   Napa had one that they said was exact same and met all the same requirements.. $60      Since I am retired and trying to be frugal... (cheap)  LOL..  I went with the Napa one.

Big difference..    This one comes on partially at 180*   Full roar at 210*      It will cool the motor down to 170 then shuts off..

But it seems to engage a LOT..   Running on level ground ,65 MPH no ac on, outside temp 80* it will kick on/off often..  20/30% engaged, not full Roar...     Have not had a chance to take it to any mountains to see if it will keep temps down or not. (we are going to Kentucky this weekend, but dont know if we will hit any long climbs near hopkinsville KY)

 So my question to all you chevy 454 owners is, does your fan clutch  engage a lot?  How often and at what temps?

Bob n Sharon
2008 Outlaw 37' Toyhauler
2 Yamaha Majesty's
Northern Indiana


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  • Hardcore Gearhead
Re: Chevy 454 Fan Clutch. How often does it run?
« Reply #1 on: August 10, 2016, 03:44:37 PM »
On my old 1984 GM P32 chassis, mine would come on quite a bit when towing my 24' enclosed race trailer, not as much when just flat towing the Jeep.

After the first year with that motorhome, I then went one step further and put an electric fan on my auxiliary transmission cooler to assist.  I wired in a toggle switch parallel with the electric sending unit so I could manually turn on the electric fan for the transmission cooler when approaching a grade and I knew I would need it.  This helped me get a handle on controlling the heat before the engine and transmission temperatures actually started to climb.  I ran around most of the western U.S and into Canada with this setup for six years and it worked great.  Never an overheating issue no matter the ambient temperatures we traveled in.

2003 Monaco Dynasty Baroness
2011 Jeep Wrangler Unlimited
FMCA# F315002


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Re: Chevy 454 Fan Clutch. How often does it run?
« Reply #2 on: August 10, 2016, 08:33:19 PM »
So my question to all you chevy 454 owners is, does your fan clutch  engage a lot?  How often and at what temps?

Mine only comes on when I expect it to, such as if going up a long hill. But don't expect it to always agree with your coolant temps, the fan clutch works by the heat near it. not the coolant temps--and they can be quite a bit different.  I never had any over heating problems with mine under any conditions that I have been in so far.

-Don-  SSF, CA

-Don-   AA6GA

2000 Fleetwood Tioga 24D, 7.4L

Nine  motorcycles:
1971 BMW R75/5
1984 Yamaha Venture
2002 Suzuki DR200SE
2013 Triumph Trophy SE
2016 Versys 650 LT
2016 Moto Guzzi Stelvio
2017 Zero DS ZF6.5
2017 Zero SR 13 w/pwr tank
2017 H-D RoadGlide Ultra FLTRU

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  • A Luddite with a stupid phone
Re: Chevy 454 Fan Clutch. How often does it run?
« Reply #3 on: August 11, 2016, 01:29:33 AM »
I have a napa one also and an additiona 48 platel trans cooler with a thermostatically switched fan. Engine rarely goes over 210* tranny stays mostly 140-180*. I don't think my new clutch fan has ever engaged fully it just doesn't make that much noise. I did have my original radiator recored with the biggest core that would fit the tanks, 4 core with 1/2" tubes I think. My original core was silted up and failing, I had the same kind of temps as the original post. I do not worry about cooling system at all any more.

Bill & Nan
93 bounder 34, chevy chassis
couple of aircooled vw's, 1 fast(sold), 1 reliable(sold).  Dubless : (
USN '76-'80, 1 boat, USS Blandy, DD 943.
I'm an analog guy in a digital age.


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  • Central IL
Re: Chevy 454 Fan Clutch. How often does it run?
« Reply #4 on: August 11, 2016, 10:21:34 AM »
My first motorhome (a 1994 Thor Residency 35') was the same vintage as yours, although on the Ford chassis with the 460... which I assume runs pretty similarly to the 454 in terms of powering a large motorhome.  Our fan clutch came on pretty often too, and I got to the point where I could predict it based on upcoming hills or off-ramps.  It would often kick on when I slowed down and took an interstate exit for instance, since the regular engine fan speed would drop temporarily and temp would climb a bit as a result.  Once I was used to wind-up and roar of the auxiliary fans, I usually liked hearing them kick on because I knew the system was staying cool.

If the fans seem really loud and you have never replaced/reinforced the insulation on the bottom of the "doghouse" cover, that maintenance item can cut down substantially on sounds and heat making its way into the coach from the engine compartment.  Check out threads here and here for some discussion on that.
Scott, wife, 3 boys... and the dog
- 2008 Forest River Wildwood 32BHDS
- 1995 Chevrolet Suburban C2500 tow vehicle
- 1994 Thor Residency motorhome... owned 2007-2012

Clay L

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Re: Chevy 454 Fan Clutch. How often does it run?
« Reply #5 on: August 11, 2016, 12:03:11 PM »

My first motor home was a 1995 P30 (1994 chassis) with a 454 and the service manual had a procedure for checking the fan clutch. They said to measure the temp of the AIR coming out of the radiator. I used a metal meat thermometer. I had to drill a small hole in the plastic shroud around the fan so I could get the thermometer between the fan and the radiator.
They said to block the radiator with cardboard and run the engine at about 2000 RPM to get the engine to heat up.
The fan will spin before it's fully engaged, but it's obvious when it engages because of the noise.
It should engage at an air temp between 165'F and 195'F. If it doesn't it should be replaced.
Clay (WA5NMR), Lee (Wife), Katie & Kelli (cats), Sali (toy poodle)
Settled down after full timing for eleven years and snowbirding for one year in a 2004 Winnebago 35N Sightseer, Workhorse W 20 Chassis. Honda toad


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Re: Chevy 454 Fan Clutch. How often does it run?
« Reply #6 on: August 12, 2016, 01:52:51 AM »
 It could very well be, due to the age of your m/h, that the seals around the fan shroud are worn, or non existant, check all around the shroud for this condition.>>>Dan
Vary rare American Tradition 38TT/330 turbo Cummins
Last year Jeep liberty 4 down
72 VW Baja 4 down
Cedar City, Utah
USAF vet. 59-63
FMCA F312919
The difference between intelligence & stupidity is: intelligence has it's limits
      Albert Einstein.


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Re: Chevy 454 Fan Clutch. How often does it run?
« Reply #7 on: May 24, 2019, 02:58:00 PM »
The P30 service manual states....

The fan speed operates 95% of the time on low speed.

The clutch fan should be viewed as a 2 speed fan...low & high.

This type of fan drive also helps maintain design temperature differential between inlet temperature and outlet temperature to a 10F and 15F differential at maximum engine speed and load.

During operation when radiator discharge is is approximately below 150F the fan is limited to 800-1400rpm's

When radiator discharge air goes above approximately 150F the bi-metal coil tightens providing max fan speed of approximately 2200rpm's.

The clutch fan is calibrated so that with a road load at an ambient temperature of 90F the fan is at the point of cycling between low & high
1994 Fleetwood Southwind Storm 28ft
GM P30 454 TBI w/4L80E trans
58,306 miles & counting....(as of 05/2019)

Professionals built the Titanic...Amateurs built the Ark.

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