Broke Down – Bad Fan Clutch

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We left Pensacola after church yesterday and everything was going smoothly until about 4:15 this afternoon. We filled up with diesel at Love’s Truck Stop in Booneville, Missouri, and shortly after getting back on I-70, the bus overheated. It happened while climbing a steep grade with a guard rail right next to the road. When the engine shutoff light came on, I hit the over-ride button and tried to get to the top of the hill, but the engine died anyway, leaving me blocking the right lane in the rain with traffic coming up behind us.

Paulette called 911 while I prayed and worked on the bus until it restarted and we managed to pull off the road, stranded in the middle of nowhere. After figuring out that the fan blade wasn’t turning despite the bus reaching around 220 degrees, we parked the bus in a remote lot and drove back to Love’s Truck Stop in the car. I called Prevost on the way and arranged for them to overnight a new clutch to Love’s. By then, it was almost 5 p.m.

I then realized there must be a way to lock the fan to keep it turning all the time. I reached the Prevost mechanic before they closed, and he guided me on how to locate the four bolts to lock the fan. Thankfully, Paulette used her Droid to find a campground about 2 miles from Love’s Truck Stop. I locked the fan, drove the 15 miles to the campground, and now we’re set up with full hookups for the night.

The mechanic advised that driving without the new clutch is possible, but it will drastically reduce fuel mileage. We’re about 1400 miles from our destination in Yellowstone.

I have a couple of questions: How difficult is it to replace the clutch? I have a full set of hand tools but no special tools.

Also, has anyone had experience locking their fan and monitoring fuel mileage until a permanent fix was made? Thanks in advance, Dale.

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Hi Dale,

I recall someone posting last year about changing their clutch, and they even included photos of the process. If you need to replace it, any mechanic shop should be able to handle the job.

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Dale,

I changed my fan clutch. See this article.

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It is not a real hard job, just takes time and patience.

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Dale, when you mentioned stepping on the override, could you explain what that is and where it’s located? I’d really like to learn more about it. Thanks!

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Sid,

The override switch is a black switch located on the left side of the driver’s floor area. It lets you engage it to help get off the road when the bus starts shutting down for various reasons.

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Andre,

Great article, thanks! I just realized I didn’t check the electrical connection to the fan. Does anyone know where this connection comes from and if it’s 12 volts? Can I connect a voltmeter to the connector, turn on my dash air, and expect to see 12 volts there? I might have ordered a clutch I don’t need. At the time, I was just trying to cover all my bases so I could have the part delivered tomorrow.

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Dale, sorry to bug you with your own issues, but does every Prevost have this override switch? I’m in the bus and can’t find a black switch on the left side. Could it be located on the footrest on the left? Thanks for your time, and I hope you get your problem sorted out.

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Sid,

I thought all Prevosts had the switch. On mine, it’s located on the floor, about 6 inches to the left of the steering column. Maybe they moved it or discontinued it at some point.

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Dale,

I’m not sure of the best way to check the voltage. Perhaps you could create a pair of extension wires to run out past the rear of the engine, then start the engine and turn on the dash air. You should get 12 volts at the end of the wires. Maybe someone else can provide details on where the power comes from.

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Sid,

On my bus, the override switch is on the left side switch panel. It’s the last switch to the left of the steering column.

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I see that the Prevost manual indicates the fan is controlled by the engine coolant temperature and air inlet temperature, but it doesn’t provide much more detail, so that’s not very helpful.

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Dale & Andre, Thanks I found it on the dash  Well I learned something today! Thanks

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Dale,

I’m not sure about the fuel mileage impact with the fan locked. However, we recently completed a 2000-mile trip from Montrose, CO to Helena, MT, and back with the dash air on the entire time. The fan ran continuously while the air was on, and the pro-driver showed 7.4 mpg for the trip.

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Larry,

I was thinking the same thing since I’m running my dash air all the time. I might just wait to change the clutch until later. Thanks!

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The fan has been reported to require up to 30 HP, so running with it locked will impact fuel mileage. Using the small bolts to lock it should be considered a temporary fix. For those who aren’t familiar, I think I posted an article once detailing how to lock the fan blade.

Overheating an engine can cause severe damage, so it’s crucial for all owners to regularly monitor their engine gauges. In very hot weather, you can observe the engagement and disengagement of the fan blades by watching the engine temperature cycle up and down. There are generally two stages: one around 204°F and another around 208°F (these are approximate). These stages should be noticeable. The override should be used only as an emergency measure, as continued use may harm the engine.

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