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Old 04-07-2016, 03:17 PM   #1
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Danfoss Speed Controller rpm Increase

I have a Cat C-9 engine in my 2005 CC inspire. Since I had my leaking aluminum radiator changed three years ago to a steel & copper radiator my fan isn't running fast*enough in low speed to maintain a constant 200 to 205 temperature. The engine temp will climb up to 206 the fan switches to high and runs until the temperature reaches 190 degrees. This cycle continues constantly regardless of the ambient temperature or weather or not I'm climbing a grade. What I would like to do is increase the fan's low speed rpm enough to maintain a constant temperature when not climbing grades or driving in high outside temperatures. I have a Sauer Danfoss fan controller #1090385 my controller inputs are from the ECM. My fan defaults to high speed whenever power is not present to the controller. That being the case, can I*simply add*an in line resistor to the 12 volt power going to the hydraulic control valve. My logic is if I can lower the voltage going to the hydraulic control valve, a little, that in turn will allow the valve to close*a little more allowing more*hydraulic fluid to the fan motor.

Does my logic sound plausible? Any compelling reason why I shouldn't try to add a resistor to the 12 volt power supply line going to the hydraulic control valve?

RJ 2005 CC Inspire #51264

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Old 04-11-2016, 12:05 AM   #2
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Good luck verifying your thoughts to be correct-
I know there are a few iRV2 members who could answer in a knowledgeable way but I am unsure how often they are on.
No matter what- Good Luck and Happy Camping.

Damon Diva ( Formerly Known as MonacoMama)
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Old 04-11-2016, 07:07 AM   #3
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Was the 200 to 205 the normal temperature swing prior to you repair?

The reason I ask is that when I bought my RV the temperature lived at 195 all the time only climbing a bit on steep grade pulls. I discovered the danfoss pump was running on high all the time and has probably been that way since I bought the rig. After I replaced the danfoss hydraulic pump my new normal is that as soon as the temperature hits 206 it cools down to 202 and then climbs back to 206 and then back down. Outside air temperature differences has no effect. My controller part #1090675 is different from yours.

In talking to the people at Action Hydraulics in Miami who ordered the pump for me, Danfoss programs the pumps based, in my case, on Freightliners specs. You may want to check with Danfoss or a hydraulics company that deals a lot with Danfoss to make sure you got the correct pump and that it is programmed correctly. And, if the pump can be programmed differently to accomplish what your after.

Best of luck, Jeff.
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Old 04-11-2016, 05:55 PM   #4
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I am not real familiar with your system, but I wonder if you could use a lower temperature engine thermostat and accomplish the same thing? It wouldn't be very expensive to try.
2012 Winnebago Tour JD
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Old 04-13-2016, 07:23 AM   #5
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Fan Speed

Yes my fan has always switched to high speed at 206 degrees and then switches back to low speed at 190 degrees. However, with my new copper & steel radiator the temperature rises from 190 to 206 relatively quickly. My thoughts are, if I can increase the fan's low speed a little it would take longer for the temperature to reach 206 thus turning the fan to high speed.
I thought that by doing this I could get a little more efficiency from the fan and increase my fuel economy.
Steve COH,
I'm running a 180 degree thermostat now, don't think I want to go any lower.
RJ 2005 CC Inspire #51264
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Old 04-13-2016, 07:39 AM   #6
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Dont know about "adjusting" speed on the electrical side of the controller but believe I have heard about installing an adjustable damper in the hydraulic line side to raise the lower limit for fan speed. Also heard there were removable shims/discs in the fan motor control head that physically calibrate fluid flow and in turn, motor rpms.....
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Old 04-17-2016, 08:38 AM   #7
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Adjusting Fan Low Speed

Old Scout,
Installing an adjustable damper in the hydraulic line side sound like what I'm looking for.
Can you give me any additional information as too who I might be able to contact.
2005 Inspire #51264
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Old 04-17-2016, 09:06 AM   #8
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A few considerations for you. Many of us have seen about a 5 degree drop in standard temperatures by changing over to Final Charge. (I have.)

The current fan control module has three speeds of low/medium/and blast off high! Check out the Source Engineering Wax Valve solution.

I was beginning to have intermittent problems with our fan controller which of course defaulted to blast off high speed. I was always able to get it to start working again by cleaning the harness plugs with electronic cleaner, and a small application of electric grease helped too. But, I felt it was on it's way out. And knew of many coach owners that were on their 3rd unit replacement, so did not want to get into that cycle.

The Source Engineering advantages are:
-Infinitely variable speed of fan based upon current temperatures.
-KISS also equates into less things that can go wrong
-I expect this to be a one time repair, and costs were close to a new Fan Control Module

I really liked the infinitely variable speed fan, as that meant the fan was only consuming/diverting as much HP form the engine as needed to keep things cool. This meant that more HP was available for the drive wheels.

Check out the Thermal Conversion Kit

Source Engineering Inc | Custom RV Chassis | Eugene, OR

Many CC owners have had good luck with this, as well SOB's too!

Best of luck to you,
Roo II is our 04 Country Coach Allure 40'
OnDRoad for The JRNY! Enjoy life...
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Old 04-17-2016, 09:52 AM   #9
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Looked at the Source Engineering solution but didn't like the idea of cutting/welding a flange into the existing coolant lines. I have the wax valve config on my 03 Alpine as OEM, and it has some issues too with regard to fan speed at low engine temps and no interface to dash A/C in the event dash A/C condenser is on the engine radiator stack.
Suspect any hydraulic shop would have access to an in-line damper. Berendersen Fluid Power was the supplier for our brand of coach.

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