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fan speed

Yahoo Message Number: 101291
During a recent trip here in Texas I noticed that my engine fan appeared to go to high & stay on high while running my dash air. I know the controller senses "head pressure" on the A/C unit & regulates fan speed accordingly, but should the fan stay on high? While running the dash A/C my engine temperature definitely runs cooler since fan is running faster but I'm pretty sure there is an adverse effect on my mileage also. Could this be indicative of an A/C issue?

Separate topic. While my fan is on high--and only on high, I hear a distinct "whine"---similar to a power steering pump on a car that is low on fluid. The whine changes in pitch with engine RPM so I suspect the hydraulic pump is the source. When I bought this coach 3 years ago I had the PTO wet kit installed. I assumed it was installed correctly but could this be a potential source of the noise? Does anyone have any thoughts on what may cause this "whine"?

Thank-you in advance for your input

Fred Compton

2005 Magna # 6454

Cat C13 w/ Allison 4000 transmission

Re: fan speed

Reply #1 –
Yahoo Message Number: 101292
My fan is designed to default to high any time the dash ac is selected. I have other fan issues right now that are unrelated. This also can be used to force the fan into high and the other way is to pull the fuse.

Re: fan speed

Reply #2 –
Yahoo Message Number: 101298
Fred,

I'll tell you how my Magna A/C fan speed correlate which, I think, is the correct program.

When I run my dash air only the fan will cycle with head pressure, coolant temperature and charge air temperature. I can verify this by monitoring the temperatures on the Silverleaf.

When I run the dash air and the rear chassis air found on Magnas and above, the program assumes a large A/C load and directs the fan to run on high full time. Like you, I can monitor this with lower temps for both the engine coolant and transmission. Yesterday Jan and I were running through western Missouri and easter Kansas at 100+ degrees.  Had the dash and bedroom air running. Even though driving west in the afternoon sun we were perfectly comfortable throughout the coach. The cost is about .5 MPG if I guess right. Even with adverse wind we still achieved 7.6 MPG.

They way to verify that your fan controller is working is drive early in cool temps for a while and watch temps to see if they rise as you expect.

Good luck.

George in Birmingham(currently on the way to Estes Park, CO) '03 Magna 6298
George in Birmingham
2003 Magna 6298

Re: fan speed

Reply #3 –
Yahoo Message Number: 101300
George,

Thanks for the explanation. I was in fact running the rear air on this particular trip which explains why the fan remained on high. Didn't realize the fan controller was programmed in this manner.
Fan controller was replaced last fall & appears to be operating as it should---for now!!

Thanks again,

Fred Compton
05 Magna # 6454