Broke Down - Bad Fan Clutch

[dale farley]

I see that the Prevost manual says the fan is controlled by the engine coolant temperature and air inlet temperature, but there are no other details, so that doesn't help me very much.

[Sid Tuls]

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

[Larry W]

Dale
Do not know about poor fuel mileage with the fan locked. We just made a 2000 mile trip from Montrose, CO to Helena, MT and back with the dash air on for the entire trip. The fan runs all the time the dash air is on. The pro-driver showed 7.4 mpg for the trip.

[dale farley]

Larry,

I was thinking that same thing, since I am running my dash air all the time. I may just wait until later to change the clutch. Thanks

[Jon Wehrenberg]

The fan has been reported as requiring up to 30 HP so running with it locked up is going to impact mileage. The use of the small bolts to lock it should be considered a temporary fix. For those unaware I think there was an article I posted once that shows the details of locking the fan blade.

The quickest way to destroy an engine is to overheat it. For this reason all owners should make absolutely certain they scan the engine gauges regularly. In very hot weather we can see the engagement and disengagement of our fan blades by watching the engine temp cycle up and down. There are two stages, one at 204 and one at 208 (going by memory so these are guesses) and they should be detectible. The use of the over ride should be considered an emergency procedure only and continued use may damage the engine.

[george frudakis]

Jon
Could you please give me the article that you posted on detail of locking the fan blade. I am new and would like to see this just in case i need to do this procedure.

[Jon Wehrenberg]

George,

Go here and scroll down to the article.

http://forum.prevostownersgroup.com/content.php?21

[truk4u]

Dale,

Here is Andre's post for the fan change out.

http://forum.prevostownersgroup.com/...y-Andre-Ducote

[dale farley]

The Prevost Maintenance Manual also shows the location of the bolts on page 5-13. I continuallly monitor my gages while driving and had seen nothing unusual all day. When I left the truck stop, within 10 miles, I was hot and the light came on. I verified there were no leaks and that the fan was barely turning. Because of time constraints, I somewhat panicked and ordered the clutch before Prevost closed for the day. In retrospect, I should have verified my 12V connection to the fan clutch before ordering a new one. I find it difficult to believe that the clutch would just fail all at once unless electrical problems are involved, either internal to the clutch or external.

[Jon Wehrenberg]

The clutch is controlled by DDEC and all I know is it is a two stage, with the first lower speed stage kicking in around 204 and the second and higher speed fan stage at around 208 (going solely based on memory). The signal to the fan clutch is via DDEC. I don't know anything about how it works or if there is a test to determine if the DDEC output is functioning, but that is where I would start checking. My guess is if the connection has been good, it is not likely it would suddenly go bad. I can envision a bad or broken ground wire though.