Engine fan?

[MarkEkberg]

Should you be able to hear and feel it engage and disengage?



Today temps were about 75, cloudy.



Running at 70mph you could hear the fan, and feel a whole truck vibration. Very small and high frequency vibration.



Fan would engage for 10 seconds and disengage for about 15 seconds.







is this right?

 

[rbattelle]

The 2003 trucks (possibly up to 2005?) have a known issue with the wire bundle going to the fan clutch chaffing against the radiator. This can cause the fan to engage at unusual times. In addition, chaffing issues with the wiring at the A/C clutch can cause strange electrical problems that can manifest as a fan clutch that engages at inappropriate times.



When the fan comes on at that speed, yes you'll feel and hear it. But the real issue is that the fan shouldn't be coming on there unless the engine is overheating.



Begin by checking the fan clutch. With the engine off, spin the fan by hand. It should "freewheel" no more than 1 revolution (and likely much less than that). If it freewheels for more than that, the clutch is shot.



Check the wiring harness that runs up the backside of the radiator for chaffing issues. Also check the A/C compressor clutch wiring for chaffing.



You may also try driving on the highway with the A/C off and see if the fan continues to engage as you describe. It sounds to me like the fan is engaging every time the A/C compressor comes on.



-Ryan

 

[MarkEkberg]

Will do. Thanks for the info.

 

[MarkEkberg]

Dug into it today. Wiring to the fan switch looks very good. There is a hard plastic piece of channel it goes through from the plug to the fan itself.

Wiring at the ac clutch looks decent as well. Looks like it had been move around due to oil filter coming out through there.

I know the temp gauge is just a idiot light, but it does not move once up to speed.

Will have to pay attention to it more and see what happens.

 

[Joseph Donnelly]

Turn the ignition key on-off-on-off-on and see on the odometer screen if you have a DTC. When the fan clutch gives problems, you should have a companion DTC.

 

[MarkEkberg]

Just did it, and all I saw was done. Will do again if I hear it at odd times. Didn't know about that little feature.

 

[B.G. Smith]

Do a close inspection of the AC clutch/compressor, could be that is what you are hearing. bg

 

[HHhuntitall]

Uhhh..... correct me if I'm wrong, but doesn't the A/C compressor signal also call for a partial fan clutch engagement?

 

[Bill Stockard]

Uhhh..... correct me if I'm wrong, but doesn't the A/C compressor signal also call for a partial fan clutch engagement?

Yes it does depending on the high side pressure via the A/C Pressure Transducer and the Powertrain Control Module (PCM). The cooling fan clutch operation can be checked with the DRBIII scan tool.



Bill

 

[MarkEkberg]

When messing around today, I tried spinning the fan. It would stop in a 1" or 2" when I tried spinning it and letting it freewheel. From previous post it sounds like it should rotate more?

 

[HHhuntitall]

No, it sounds good to me. What you are hearing is when the A/C compressor engages, it sends a signal to the fan to engage. When the compressor kicks out, the fan does, too. There shouldn't be a vibration, though... . Is it a bad vibration, or just something you can barely feel? At 175K, it's possible the fan bearing could be getting rough... ...

 

[MarkEkberg]

The vibration is felt in the three pedals, and in the steering wheel. Just barely, and you can hear a difference.

It would seem to me that at HW speeds there would be no need for it to turn on? Or it should stay on for longer periods of time?

 

[Bill Stockard]

When my '03 was new, there was a vibration each time the A/C compressor clutch engaged and continued until it cycled off. I could hear it and feel it in the steering wheel and the brake and accelerator pedals. (automatic trans) I returned to the dealer and they discovered the compressor mounting bolts weren't tight. They tightened them and I've never heard/felt the vibration since.

Bill

 

[MarkEkberg]

Interesting... ... . I will check this out tonight. Been doing all the easy trouble shooting recently. Love the easy and free fixes.


It had a water pump done last october so I have to rule out a bad bearing, but things like that have happened to me before.

 

[rscurtis]

The fan in my signature truck will only ramp up if the truck is in traffic with the AC on. It has never come on to cool the engine, even after sitting in a three-hour traffic jam one summer day waiting for an emergency repair on the George Washington Bridge. Perhaps it would be required after some time, but all I would do as soon as the temp. gauge went north of 205* would be to momentarily turn on the AC and it would immediately cool the engine back to 190*.

 

[STEVEBROOKS]

Saw the above stating the fan shouldn't freewheel any more than one revolution, so I checked that on mine. Though there's some slight resistance when spinning it either direction, it will spin more than one revolution. I've never had a hint of a cooling problem, even at altitude in New Mexico in the summer when towing my 5th wheel toyhauler. Does the freewheeeling truly indicate the fan clutch is bad?

Steve

 

[rbattelle]

Saw the above stating the fan shouldn't freewheel any more than one revolution, so I checked that on mine. Though there's some slight resistance when spinning it either direction, it will spin more than one revolution. I've never had a hint of a cooling problem, even at altitude in New Mexico in the summer when towing my 5th wheel toyhauler. Does the freewheeeling truly indicate the fan clutch is bad?

Steve

The service manual says if it rotates more than a few revolutions (I forget the exact count, and can't find it in the manual right now) then the clutch is faulty. I would say if you've never had any overheating issues then don't worry about it, your fan is working fine.

-Ryan

 

[HHhuntitall]

All those wires going to the fan clutch are power wires and sensor wires. The A/C calls for a partial fan engagement, depending on head pressure, it send the signal to the fan, where the valve in the fan clutch actuates, actuating the fan, usually only partially. The speed sensor sends a signal to the ECM telling it what speed it is at, % wise, and that signal is used to tell the clutch to engage at a higher % or disengage. How much your condenser, intercooler, radiator is stopped up with help dictate this %, as well as ambient air temps, water temp, and throttle position... ...

 

[MarkEkberg]

So I took truck to work this morning with nothing turned on. No vibration, or noise at any speed.

Tired and forgot to turn ac on on my way home to try and reproduce. I did check the mounting bolts. I got about a 1/2 turn out of them to make them tight.

Will know more in the future.

 

[Tinman]

What should the A/C pressures be? My fan seems to be coming on oddly and frequently. I figured it was a bad clutch and was going to replace it but it looking like I need to do some more diagnostics. A few years ago, my blend do broke and before I figured out that was the cause of my poor A/C function, I put a can or 2 of 134 in. It could be over charged.