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Discussion Starter #1
I have a 2005 F350 6.0 with a cooling fan that turns on after the engine warms up. At 210 the fan comes on and will not disengage as long as I'm driving around town. It will eventually disengage if I get it up to 60 mph or greater. I checked the wiring harness and all looks good. I'm suspecting the fan clutch but want to verify before I spend any more $ on this.

Has anyone had this issue before? If so, what was the fix?

A little more background:
I was hauling a container (heavy load) when I noticed the fan started coming on at 212 instead of 220, which it always did before. It would kick on at 212 and cut out at 202. A couple of hundred miles later it started kicking on at 208/210 and cut out at 198. I found a coolant leak at one of my stops and found it was coming from the seam of the degas bottle. Replaced the degas bottle and cap and the leak was fixed, but my fan issues continued. The code I get is P0528 Fan Speed Sensor Circuit No Signal.

Any help would be appreciated.
 

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I have a 2005 F350 6.0 with a cooling fan that turns on after the engine warms up. At 210 the fan comes on and will not disengage as long as I'm driving around town. It will eventually disengage if I get it up to 60 mph or greater. I checked the wiring harness and all looks good. I'm suspecting the fan clutch but want to verify before I spend any more $ on this.



Has anyone had this issue before? If so, what was the fix?



A little more background:

I was hauling a container (heavy load) when I noticed the fan started coming on at 212 instead of 220, which it always did before. It would kick on at 212 and cut out at 202. A couple of hundred miles later it started kicking on at 208/210 and cut out at 198. I found a coolant leak at one of my stops and found it was coming from the seam of the degas bottle. Replaced the degas bottle and cap and the leak was fixed, but my fan issues continued. The code I get is P0528 Fan Speed Sensor Circuit No Signal.



Any help would be appreciated.
Sounds like a bad fan clutch to me. Basically the same symptoms I had when mine started before it locked up completely. How does it feel if you spin it by hand? Good news is its a pretty easy job that should only take a couple of hours if you have never done one before.

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Discussion Starter #3
Thanks for the response. When spinning the fan by hand it feels the way it should, there's a bit of resistance but there's no binding or grinding feel to it.
 

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Thanks for the response. When spinning the fan by hand it feels the way it should, there's a bit of resistance but there's no binding or grinding feel to it.
The other possibility is that there is a wiring issue somewhere. I checked my wiring by using an ohmmeter and checking for continuity between the fan connector and the proper pins at the PCM.

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Discussion Starter #5 (Edited)
I've done just about everything on the outside of this truck, including a total bullet proof engine rebuilt, but I've never had to mess with the PCM. Is it hard to get to the connectors?

Ah! Just did a quick search and found where the PCM is. Which connector is the one that has the wires for the fan?
 

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Tested all the wires and they are all good. I'm getting continuity on all wires and power on the PCM power relay, switched power. Pretty confident the fan clutch is bad. I'll replace it and report back.

Thanks for the help letsmow10 appreciate it!
 

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Tested all the wires and they are all good. I'm getting continuity on all wires and power on the PCM power relay, switched power. Pretty confident the fan clutch is bad. I'll replace it and report back.



Thanks for the help letsmow10 appreciate it!
No problem. Let us know how it goes. On a side note... when replacing the fan do NOT cut your fan shroud. Remove the 2 brackets that hold the radiator in and the electrical cable in front of the radiator. That will allow the radiator to move enough to pull the shroud up and out easily.

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Discussion Starter #11
Yes, I have an SCT Livewire through which I monitor ECT, EOT, TFT (Tranny), EGT and a bunch of others.

I've done a mod to the oil cooler and it's no longer 2 in one with the coolant. Oil temps are running slightly higher than ECT but that's normal for this set up. It's usually within 10 to 15 degrees.

One other thought I had was related to the AC. I had my AC charged after reinstalling the engine and one line wasn't tight, which I noticed after I had it serviced. I cranked it down and tested the AC, which seemed to run fine in February/March. I live in Texas and we get warm days at that time of year. Now that it's summer I noticed the AC is not as cold, probably because of the charge being low. I was running the AC while experiencing the fan issue. Any way the AC might be adding to the problem or causing the fan to stay on at low speeds?
 

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if your AC is on and you're going low speeds your fan clutch will always probably be on trying to pull air through the condenser. You want it on if you want cold AC at low speeds.
 

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"Any way the AC might be adding to the problem or causing the fan to stay on at low speeds?"

Yes, the fan speed is kicked up when the ac is on for increased air flow over the condenser -- you would have to turn the controls to off to see the fan decrease in speed -- if you monitor engine load(which also affects the fan speed), you can tell when the compressor is running

Basically the logic that operates the vistronic fan clutch tries to anticipate engine heating and get a jump on controlling heat -- while when not needed, lets the fan coast and save fuel
 

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Discussion Starter #15
I finally replaced the fan clutch after confirming it was not related to AC. Unfortunately the problem persists. It now varies when the fan come on and off.
1) It comes on (locked in 100%) right at start up and stays on up until my speed is over 50 mph when it shuts off. When I slow down, like coming to a stop light, it comes back on.
2) It doesn't come on until after the engine is warmed up and only after I shut it down and restart. Since I'm mostly in town driving the coolant temp hasn't climbed above 190 degrees so the fan hasn't kicked on to cool the engine down like it normally would if the coolant temp climbs to 210 or above.

Anyone experience this before? I feel like the issue is something simple but it eludes me. Does anyone have information on what exactly are the inputs (sensors, RPM, AC) that make the fan turn on?
 

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my truck does this but only say once every few months and has for the decade plus i have owned it

but i am not sure why you experience this all the time
Yours does this when the internal reservoir drain is at or near the bottom -- when the clutch sits for a time with the drain in the lower position, the fluid will enter the area where the circular rings are -- driving the clutch until the fluid is pumped out into the reservoir again

All viscous fan drives will do this -- just is what it is -- the fan will run for a short time, then return to low/coast until the valving opens and transfers the fluid back into the circular ring area -- if the reservoir drain is pointed upward, this will not happen
@leosabo
A fan clutch that runs every time the engine is started is either over filled with fluid or the reservoir partition is not sealing -- live with it or get another

Your monitor system should read fan RPM, if not then, Torque or Forscan will

I would suggest unplugging the fan harness and observing if the running too fast when started, is diminished at startup -- must determine if the problem is electrical or a defective fan clutch
 

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I finally replaced the fan clutch after confirming it was not related to AC. Unfortunately the problem persists. It now varies when the fan come on and off.
1) It comes on (locked in 100%) right at start up and stays on up until my speed is over 50 mph when it shuts off. When I slow down, like coming to a stop light, it comes back on.
2) It doesn't come on until after the engine is warmed up and only after I shut it down and restart. Since I'm mostly in town driving the coolant temp hasn't climbed above 190 degrees so the fan hasn't kicked on to cool the engine down like it normally would if the coolant temp climbs to 210 or above.

Anyone experience this before? I feel like the issue is something simple but it eludes me. Does anyone have information on what exactly are the inputs (sensors, RPM, AC) that make the fan turn on?
Not saying this is the case but a new fan clutch can be bad. I had one myself. Like Hydro said, disconnect the wiring harness and see if its electrical or mechanical. Use a scanner to read fan RPM with the witing connected.

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Thanks to all those who responded! Fan is now operating normally!!! Yay!

I hooked up my scanner and cleared the P0528 code and then took it for a long drive. At first it came on as before but after a while it cycled off and stayed off until I was on the highway and the coolant temp got to 210. It cycled on but only at partial speed and only for a few seconds. Previously, it would cycle on to 100% and would spin at the same speed as engine RPM. This time I could barely hear it. Once the temp dropped a couple of degrees it turned off. Drove it for about 60 miles total, highway and in town, and it works as it should.

The fix was definitely the fan clutch. Now that I have one that operates normal I can say with certainty the one I had had been going south for a while. It would go full on whenever the temp would rise to a certain degree and then off once the temp dropped. It never came on partially, which tells me it was showing signs of going out.
 

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Keep us posted ...I think you still have a problem, it's just hiding for the moment

The usual failures on that type of fan clutch includes, the bearing going out -- the fluid leaking out(will not go full speed) -- or the wiring getting broken at the fan shroud or connecting harness

Most of the time in my applications, it is the wiring -- either the speed sensor(fan defaults full on) -- or the valve coil(fan always at idle)
The speed sensor failure sets a code
 
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