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Old 03-08-2016, 01:20 PM   #1
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Radiator fan speed

Have a 08 Winnebago Vectra, ISL 425 cummins rear radiator. When I start the engine the fan is blowing full blast until the engine warms up (3-5 min.) then speeds down as far as I can tell. Goes against logic-shoundn't the fan turn only when the engine needs the air movement to cool it down. Do I need the ecm programed. Not the best mileage (7-8 mpg) and not the best performance. 40,000 miles. All filters changed including air and regular maint. Any ideas, especially concerning the ecm. I've read they sometimes need to be re-programed. Cost? Thanks
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Old 03-08-2016, 03:28 PM   #2
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Quote:
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Have a 08 Winnebago Vectra, ISL 425 cummins rear radiator. When I start the engine the fan is blowing full blast until the engine warms up (3-5 min.) then speeds down as far as I can tell. Goes against logic-shoundn't the fan turn only when the engine needs the air movement to cool it down. Do I need the ecm programed. Not the best mileage (7-8 mpg) and not the best performance. 40,000 miles. All filters changed including air and regular maint. Any ideas, especially concerning the ecm. I've read they sometimes need to be re-programed. Cost? Thanks

robot,
Well, first off, most rear radiator diesels don't have a fan clutch. But, I'm not an expert on each and every one made so, if yours has one, well, so be it. Now, if so, the operation of it, may or may not be somewhat the same as how they used to work in regular autos. In those, about 99.999% of them were controlled by a bi-metal spring, that was hooked to a shaft (inside the finned clutch unit) that was turning in viscous silicone fluid.

And, as the viscosity of the fluid changed, so the fan speed. On a cold start, many would see, feel and hear, their fan clutches go to full speed or, almost full lock-up. That would cause the loud fan operation one would hear. But, after only 30 seconds or so, the viscous fluid in that clutch would tell the fan that, the fan is not needed due to the temp of the air hitting the bi-metal spring so, that fan would begin to un-lock and almost coast.

Now, the engine was not changing speed, as many thought was happening, all that was changing is the speed of the fan, would would sound as though the engine was slowing down.

But, on yours, if you have one, I have no idea how yours is controlled, either air operated or, electrical or, maybe even the same process as the old ones in cars, not a clue. But, you are correct in the fact that they do approach lockup as the air temp in whatever sensor is controlling them, heats up. These engine programmers have whatever kind of parameters set forth, to control these things. And, it might not make sense to us.
Scott
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Old 03-08-2016, 06:58 PM   #3
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Originally Posted by robt View Post
Have a 08 Winnebago Vectra, ISL 425 cummins rear radiator. When I start the engine the fan is blowing full blast until the engine warms up (3-5 min.) then speeds down as far as I can tell. Goes against logic-shoundn't the fan turn only when the engine needs the air movement to cool it down. Do I need the ecm programed. Not the best mileage (7-8 mpg) and not the best performance. 40,000 miles. All filters changed including air and regular maint. Any ideas, especially concerning the ecm. I've read they sometimes need to be re-programed. Cost? Thanks
My 2007 ISL 425 clean diesel behaves exactly as you describe. Fan runs at high speed when I first start the engine then seems to slow a bit in 2 - 3 minutes. Not sure what your mpg expectation is but 7 - 8 is not bad for this engine in any heavy coach. We are 42' and weigh 38,000 not including the weight of the F150 we tow. We average 7.4 and get as good as 8.2 on level road with no competing winds.
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Old 03-08-2016, 09:58 PM   #4
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Probably shoundn't have said "re-program" the ecm but should it be checked for any upgrades periodically and has anyone exsperienced better performance after haing it checked. Thanks for any input.
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Old 03-08-2016, 10:11 PM   #5
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Side radiator and rear radiator - different controls?. I think OP is rear. Our Country Coach are side radiators.

Brian
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Old 03-09-2016, 02:04 AM   #6
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I think someone with an engine of the same group or design would be best to steer you as to how it should operate, because they have changed things quite a bit over the years. My '07 had a hydraulic driven fan, whereas my '14 has a shaft driven fan - and the current one runs what I thought was hard at it's lowest ("0%") setting - and even harder at 100%. I thought since the same year OTR Freightliner trucks' fans move very little or hardly at all at idle, that's how mine should behave - but after many visits to the warranty station and involving FCCC, and one replacement of the ECM controlling the fan, I now know mine operates the way it's supposed to.
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Old 03-09-2016, 07:07 AM   #7
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Side radiator and rear radiator - different controls?. I think OP is rear. Our Country Coach are side radiators.

Brian
You bet. I missed in the OP that he said rear radiator. I did not think Winnebago made any Vectra's with rear radiators. When they dropped the Vectra and made the Tour their top line coach, it was a rear radiator.
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Old 03-10-2016, 12:05 PM   #8
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I run heavy trucks and they all do the same thing. Cummins, Detroit,........maybe to prevent engine warm up too quickly? Too quick of a warm up can cause sleeves to move on a ISX Cummins. My caterpillar in my old MH did the same. Fan cuts in and out on heavy trucks thermostatically, then air pressure will either engage or release the clutch.(depending on the model)Air conditioner will make fan run on on a large diesel as well. Although, a lot of MH's have a separate electric fan for the AC . I'm sure a heavy duty diesel mechanic could shed some light on this.
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