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Topic: Fan Speed Controller (Read 776 times) previous topic - next topic

Fan Speed Controller

Looking into this based on the great results reported by Calflashbob on swapping out his wax capsule fan speed controller to one with  to minimize HP loss due to fans running at high speed at unnecessarily low temperatures.  My 295 has 300 ponies max. so any incremental increases in power is appreciated.  As a side benefit Bob Rozek reports a significant increase in fuel economy after performing this modification as well.

Eager for further details, I found this document which explains motorhome fan, fan speeds, horsepower consumption of fans, and details on the wax capsule fan speed controller.  Though it says Alpine Coach, it's written by Sauer Danfoss, the mfg of our controllers and is generic across many coaches.

http://www.alpinecoachassociation.com/chassis/Radiator%20FanMotor%20Sauer-Sundstrand%20c.1996.pdf

One statement I ran across is that coaches with retarders may require lower temp controllers.  Guess this makes sense as coasting down a mountain, not much call for engine cooling but plenty for retarder cooling.  I'd be interested in knowing if anyone who's made this mod notes any difference in retarder performance (cooling) on heavy downhill grades?



Re: Fan Speed Controller

Reply #1 –
Absolutely no issues regarding the transmission temps in a variety of conditions. When I made the change I went from a controller that was stuck in high speed, probably for years. The mileage increase was dramatic .

Re: Fan Speed Controller

Reply #2 –
The only way I was able to note the over driven issue was the silver leafs RMPG. Fantastic diagnosis tool.

It would show large mpg increases on smooth flat roads in cool weather for a few miles then drop back down.  WTH?

Then eliminated all possible losses of power. 

Re: Fan Speed Controller

Reply #3 –
What rpm should the hydraulic fans run at when low and at high speed?

Re: Fan Speed Controller

Reply #4 –
Mine is also stuck on high, the proportional valve controlled by a proportional sensor would be pretty sweet setup.

Re: Fan Speed Controller

Reply #5 –
Quote from: Old phart phred –
Mine is also stuck on high, the proportional valve controlled by a proportional sensor would be pretty sweet setup.

That's kind of what you get in the Sauer Danfoss valve.  The sensor is integral, operation is proportional which modulates fan motors.  One thing, looking over the Ebay deals, and the links to them from class A owners I see recommendations for units that will work...but not properly, leading to basically on/off switches, giving you high/low range.  They need to be set or adjustable over a fairly narrow temp range.  A lot of folks installing these are trying to replace a failed electro/mechanical fairly sophisticated controller that has numerous inputs to adjust fan speed.  The FT coaches I'm familiar with have the wax valves, just with set points different from what is being recommended.
 

Re: Fan Speed Controller

Reply #6 –
Could not find the valve mentioned.