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SD Fan Controller Question

Yahoo Message Number: 114450
I was checking my fan today. When the engine is cold (75F ambient) and I start it, the fan turns quite slowly. When the coolant temp was up to about 140F it was turning quite rapidly, couldn't tell if it was on high, but it could have been. Also could have been medium. Not sure. I pulled the fuse and it stayed on whatever speed it was on at idle. Does this indicate a problem with a coolant or air sensor? Or the controller? It certainly does not start out on high. Mine is an external controlled on my C12.

Further related question: From looking at the test procedure I see the following:

CAT all others External Thermostat Controlled Fan
Fan speed Engine R.P.M. Range
Min Idle 0-500
Med Idle 500-850
Med/Engine 2.1K 1300+
Fast Idle 700+
Fast/Engine 2.1K 1.7K+

This would indicate to me that fan speed also varies dramatically with engine speed, independent of temperature, all the way up to 1700 RPM. Would this explain why, the other day, I was driving past a retaining wall at about 20 MPH and could hear the fan howl when I hit the accelerator? Clearly my fan speed is not on "high" all the time since I could make it howl by hitting the pedal. Or are we talking about "high" at idle vs "high" at say 2000 RPM engine speed?

Rich 2002 Magna
Sent from Mail for Windows 10

Re: SD Fan Controller Question

Reply #1 –
Yahoo Message Number: 114453
My unscientific test for high speed operation of the fan is to take a 8.5x11 sheet of paper and place it on the intake grate. If it is sucked onto the grate on the side of the coach and does not fall off, then it is at high speed! I used it to verify that it was running at full speed when it was not suppose to!

Herb
CCO Moderator
2007 Allure (sold and forgot the serial number)

Re: SD Fan Controller Question

Reply #4 –
Yahoo Message Number: 114460
Herb,
Your" old" '07 Allure is parked next to us here at OMC. Still looks good and the new owners are happy with it.

Don
'02 Intrigue 11427
'02 Intrigue #11427

Re: SD Fan Controller Question

Reply #5 –
Yahoo Message Number: 114462
Thank you Bill. This is very fascinating and I am printing it out for future reference. As I suspected there's a lot more to it than just the fan controller and engine speed plays a big role. I've just started reading it but I have already concluded that I'm going to change my hydraulic filters for openers since it's been four or five years at least. My fan is varying speed quite a bit so I doubt it's the fan controller. I'm wondering if the coolant or air sensor have gone out of spec. Years ago I had the coolant sensor completely fail and the fan was on high all the time. Not the case at present.

Rich
 

Re: SD Fan Controller Question

Reply #6 –
Yahoo Message Number: 114463
I will try that as soon as the winds here drop below 40 miles an hour Herb.

Rich 2002 Magna