[Archived]

Larry,

67,000 miles seem early for clutch replacement, but it could be possible. Before removing it make sure the fan locking tabs aren’t hitting the clutch. There will be a couple of tabs with holes in them that allow you lock the clutch with bolts. If this has ever done, it’s possible the tabs are now too close to the clutch.

[Archived]

See the existing article available in the ‘articles’ tab at the header. Yes, 67K seems early; I did mine at about 150K but the newer one seemed better built than the original. Also, I was told that if the coach is often exposed to salt air, it effects the life of this component.

[Archived]

The replacement of a fan clutch is something we will all face over time. They are pricey, and if you opt to do it yourself if is not so mechanically challenging as you might think, but it requires a strong back.

The clutch can be rebuilt. I just opted to replace mine which happened in the vicinity of 200,000 plus miles. I’m surprised at your relatively low mileage.

[Jerry]

we had ours replaced in nov. 2009 due to noise (60k miles +-), then had new one fail in summer 2010 on way to florida. So one never knows when a failure can occur.

The third one seems to be doing ok.

Good luck,

Chris

[Archived]

Chris’ failure rate is disturbing. Hopefully, new clutches aren’t from China. When you have a fan clutch that doesn’t engage, first rule out the cheap and easily replaced relays. My coach had 4 relays controlling the clutch, all will have at least 2. Relay contact failures aren’t always hard failures and most relays are now from China. I’d simply put relay replacement on a 50,000 mile replacement schedule.

[Archived]

Mine wasn’t engagement, but was the dreaded bearing noise. It is too easy if it is a relay. #78 and #79 I think.

[Ronald]

Relay 99 is the relay that supplies power to the clutch.

Relay 78 supplies a ground for low speed and Relay 79 supplies ground for high speed. You will also have a relays to support high speed operation with Dash Air and low speed operation with a retarder.

Testing the clutch is easy. Take a spare relay and break off the terminal blade #85. Now you can insert this into 78 or 79. When in either 78 or 79 and with the key on (engine off) there should be clutch resistance felt when trying to move the fan blade. Or start the engine and the fan should be running in low speed or high speed, depending on whether the relay was inserted in 78 or 79. If putting it in 78 and then 79 does not engage the fan, check relay 99 or circuit breaker 130 (on a 98 XL shell).

Prevost and Detroit where brillant engineering this circuit. The relays are actually energized when the fan is off. That way if a relay’s coil fails the fan will always be on rather than never on. If you buy new relays, they should be the ones with protective diodes in them. Some use resistors for protection and Prevost has sold these as replacements. They probably work fine, but ones with diodes are still available.

I bought replacement relays with diodes from onlinecomponents.com for $2.10 each. There is a minimum purchase requirement or surcharge. The part number is TE Connectivity / AMP 1432795-1

[Archived]

I was at Prevost Jax last week, and a friend of mine’s coach was next to me in the shop, an ’06 with 63k miles and had to have the clutch fan replaced do to a noisy bearing.

Mine, with a 140k, still good…………..knock on wood.

[Archived]

I just had mine replaced in Dallas at Prevost my coach has 74,000 miles on it.

[Archived]

Just had mine replaced at liberty 70,000 miles Gary

[Wayne]

I wonder what temperature the fan comes on at on the newer coaches. At 70K miles for replacement, they are either cycling a lot more often or the product quality has fallen. It could also be a factor of Prevost OTR Air. Those of us with Dash Air don’t likely have near the on/off cycles as Prevost OTR Air coaches given our fans engage after 5 minutes and stay on when Dash Air is on.

[Kenneth]

Since the age of the coaches posted seems to indicate EGR coaches I suggest OTR has nothing to do with the life. My 97 with OTR had well over 200,000 when it was replaced.

Instead I think the ECM has multiple triggers for the fan beyond engine coolant temp and AC, both driver and OTR will trigger the fan on later model DDECs.

[Archived]

The EGR coaches have the CAC air temperature activate the fan around 190 degrees and I think that the fan stays on for 2 minutes,these coaches are cycling the fan continiously.Of course the water temperature will also cycle the fan but as I watch the CAC temperatures in the Silverleaf I see that the air temperature activates the fan most of the time.

[Archived]

Jack,

I think you identified the cause. That’s a lot of on/off cycling.

Jon,

Why would OTR Air activate the fan. It’s simply another HP load on the engine. Dash Air does so to provide air across the condenser placed against the radiator or CAC.

[Bob]

You are right. Misspoke.