Eng elect fans controls for eng a/c

[cryoman]

I have a 2002 Itasca 35 U with the 8.1 eng. What controls the 2 elect fans for the eng a/c.The turn free and i have applied 12v dc to them and they run. Is there a pressure switch or other control that turns them on and off when the a/c is running. Does anyone have a wiring diagram that shows the operation of the fans?

[DriVer]

Quote:

Originally Posted by cryoman I have a 2002 Itasca 35 U with the 8.1 eng. What controls the 2 elect fans for the eng a/c.The turn free and i have applied 12v dc to them and they run. Is there a pressure switch or other control that turns them on and off when the a/c is running. Does anyone have a wiring diagram that shows the operation of the fans?

cryoman, The fans will normally cycle ON when you initially start the engine. At some predetermined time they will then cycle OFF.

The fans are used in conjunction with the air conditioning system and they may start anytime when the AC is selected.

The fans may also start-up and provide auxiliary cooling if the demand is there.

In regard to wiring, the point of origin for the fans and how they operate is determined by the engine control module (ECM) or powertrain control module (PCM).

[MoonchaserTX]

Hey DriVer,
Related question....while driving our new-to-us 2007 Winnebago Sightseer 29R home today from the dealer, I heard what sounded like the transmission shifting down but the tach was still just barely over 2,000 RPM so it wasnt downshifting. I was on a flat freeway going into a slight headwind at (about) 60 MPH, and I should add that I had the dash air on full and it was supposedly 105 degrees here in the Dallas area today...SO...I was wondering if the sound was simply the cooling fans kicking on? Are they audible from the drivers seat?
Oh also, when the noise went away, it would taper off slowly like a fan taking a few seconds to slow down with a variable speed control.
Certainly not a nusiance if that's all it is..hope that's what the sound was.

Thanks!

[kennersonf]

MoonchaserTX, I'm not Driver, but that's exactly what you heard. When the fan clutch kicks in, you can definitely hear it. To me, it's a good thing to hear the fan cycle on. I have a Scan Guage and I can watch the temperature slowly go back down and at a certain point the fan clutch disengages. If you don't have a ScanGuage II you might consider it. Just Google it and you can learn more about it.

[DriVer]

Quote:

Originally Posted by MoonchaserTX Certainly not a nusiance if that's all it is..hope that's what the sound was.

MoonchaserTX, That reassuring sound is the engine's PCM taking care of business!

[scoutmstr]

See


fans that cool allison & a/c

[MoonchaserTX]

Thanks for the info guys! I was hoping that's what it was, so that's a relief! Thanks again for the info

[edgray]

Quote:

Originally Posted by MoonchaserTX Hey DriVer, Related question....while driving our new-to-us 2007 Winnebago Sightseer 29R home today from the dealer, I heard what sounded like the transmission shifting down but the tach was still just barely over 2,000 RPM so it wasnt downshifting. I was on a flat freeway going into a slight headwind at (about) 60 MPH, and I should add that I had the dash air on full and it was supposedly 105 degrees here in the Dallas area today...SO...I was wondering if the sound was simply the cooling fans kicking on? Are they audible from the drivers seat? Oh also, when the noise went away, it would taper off slowly like a fan taking a few seconds to slow down with a variable speed control. Certainly not a nusiance if that's all it is..hope that's what the sound was. Thanks!

MOONCHASERTX:

Not wanting to leave you confused, but the answers you got were related to the large fan BEHIND the radiator, not the two small electric fans (if you have them) that can be seen from in front of the radiator. THOSE don't make enough noise to be heard from the driver's seat, IMO.

Ed