Fan Operation

[sailsmanship]

Have a 99' Ford Superduty with a 7.3 Diesel. Just took my 5000# boat on a 12 hours run from Ohio to upstate New York. Have made this run couple times before with an even heavier boat. When going up long grades, sometimes what I thought was the clutch fan would engage and run for a while until I would get to level road than shut off. Never would really give it a thought. This time however the fan, ( or what I assume was the fan) would engage and rev up and down maybe 50+ times before going off, and the air conditioning would blow warm until it went off then blow cold. It would cycle on alot more times during the trip than any time previous. What is happening?

 

[battery]

Re: Fan Operation

sounds like you got trouble with the cooling system in your truck. i would get a technician to look at it before it costs you alot of money.

 

[Silvertip]

Re: Fan Operation

Not necessarily a problem. Most "gas" powered (yes I know this is a diesel) vehicles will cut the A/C compressor off when engine vacuum drops. Engine vacuum is used to sense engine load so therefore the compressor would kick off until vacuum again rose to normal levels. While off, obviously you get no cold air. With a diesel, there is no vacuum so they use other methods of determining engine load. If the compressor is being cycled, this is normal. If it's not supposed to work that way, there obviously is a problem.

 

[Reel Poor]

Re: Fan Operation

It sounds like the fan clutch is failing and due to that the refridgerant pressures are rising beyond normal/safe levels. When this happens the refridgerant high pressure switch is cutting the a/c compressor off untill the pressure returns to normal/safe range. Most likely just need a new fan clutch. I say "just", like there's nothing to it, but aftermarkrt these fan clutches are about 200.00 dollars, and about twice that price thru the dealer.

 

[Silvertip]

Re: Fan Operation

The engine "fan" clutch has nothing to do with refrigerant pressure. The "compressor" clutch is electrical and is turned on an off by the engine management system depending on engine load and system pressure. Hence it controls system pressure. Air temperature through the radiator controls whether or not the "fan" clutch (a viscous clutch) engages or not. It is not unusual for the fan clutch to engage and disengage in regular cycles if air temps are right at the margin. A defective fan clutch will not cause the compressor clutch to disengage unless the engine begins to overheat. If that happens, the engine temp sender signals the ECU and it in turn releases the compressor clutch.

 

[STL Towman]

Re: Fan Operation

check your condensor thats what it was when mine did what your is doing

 

[JB]

Re: Fan Operation

I had what seems like a related problem on my ML320.

There is an auxilary fan that turns on if tranny fluid gets too warm. It also triggers if the A/C refrigerant isn't getting enough airflow through the condenser.

I got stuck in gridlock on a hot day at the Nevada/Utah border and not thinking, left it in drive while sitting still for 5-10 minutes at a time. Tranny fluid got hot, but the fan didn't turn on. I didn't notice anything until the 'puter turned off the A/C and disabled the drive-by-wire throttle.

Replacing the fuse for the aux. fan solved the problem and I now go to Park when sitting still in gridlock.

What's my point?

You need to find out what switches the fan on. What you describe might have been because of the hot weather, tranny cooler or A/C condenser not functioning properly.