When should the clutch fan lock up/unlock??
11-10-2007, 10:31 AM
#1
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When should the clutch fan lock up/unlock??
I started a new thread on this because I need to know how the stock clutch fan is supposed to work. Some of you have read my thread on the problems I was/am, having with my clutch fan/viscous and the wiring. So, I took this excerpt from my thread, and if you guys can tell me how YOUR clutch fan works (when it locks up,when it doesn't) that would be great, as I need to know if I wired my fan up correctly and it is currently operating like it should.
OK, and here is yet ANOTHER update. Drove my truck a couple hundred miles today. Here is the deal, and keep in mind NONE of this occured BEFORE the wires for my fan got shredded....
1)When I first start the truck in teh morning, and drive down the street, AC on, clutch fan is locked.
or....
2)When I first start the truck in teh morning, and drive down the street, AC OFF, clutch fan is NOT locked
3)After truck warms up, comes up to temp, fan clutch will unlock, and then i I am in stop and go traffic, clutch fan will lock BACK up (AC on)
4)If at any time I turn the AC off, clutch fan will unlock.
5)If I am driving down the road with AC on, and teh clutch fan is locked, and I want it unlocked, all I need to do, is turn the AC off for a few seconds, and clutch fan will unlock, and I can turn AC back on, and clutch will NOT lock back up.
6)I am now getting belt squeal when I turn engine off
7)ALL OF THIS S****
BEFORE my wires got ripped up, my clutch fan would ONLY lock up when temps started to elevate (hauling heavy load, or if I got REAL aggressive with my right foot for awhile)
So, tell me, how IS the clutch fan supposed to operate/function (in other words, when is it supposed to lockand unlock according to factory specs???)
OK, and here is yet ANOTHER update. Drove my truck a couple hundred miles today. Here is the deal, and keep in mind NONE of this occured BEFORE the wires for my fan got shredded....
1)When I first start the truck in teh morning, and drive down the street, AC on, clutch fan is locked.
or....
2)When I first start the truck in teh morning, and drive down the street, AC OFF, clutch fan is NOT locked
3)After truck warms up, comes up to temp, fan clutch will unlock, and then i I am in stop and go traffic, clutch fan will lock BACK up (AC on)
4)If at any time I turn the AC off, clutch fan will unlock.
5)If I am driving down the road with AC on, and teh clutch fan is locked, and I want it unlocked, all I need to do, is turn the AC off for a few seconds, and clutch fan will unlock, and I can turn AC back on, and clutch will NOT lock back up.
6)I am now getting belt squeal when I turn engine off
7)ALL OF THIS S****
BEFORE my wires got ripped up, my clutch fan would ONLY lock up when temps started to elevate (hauling heavy load, or if I got REAL aggressive with my right foot for awhile)
So, tell me, how IS the clutch fan supposed to operate/function (in other words, when is it supposed to lockand unlock according to factory specs???)
11-10-2007, 04:41 PM
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have you read up on clutch fans? if not here is some reading for you
http://www.popularmechanics.com/how_...e/1772922.html
http://www.popularmechanics.com/how_...e/1772922.html
11-10-2007, 10:32 PM
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Sounds fairly normal to me. I could be wrong...
The fan clutch should engage anytime the AC or defrost is on as the AC Condenser needs extra airflow over it to condense the refrigerant to a liquid for proper AC/defrost operation. If the AC is turned off or the AC pressure switch (or similar signal depending on AC system type) commands the compressor to turn off the fan/fan clutch usually turns off as well. The ECM will also command the clutch to engage/disengage with coolant temp input as well.
The fan clutch should engage anytime the AC or defrost is on as the AC Condenser needs extra airflow over it to condense the refrigerant to a liquid for proper AC/defrost operation. If the AC is turned off or the AC pressure switch (or similar signal depending on AC system type) commands the compressor to turn off the fan/fan clutch usually turns off as well. The ECM will also command the clutch to engage/disengage with coolant temp input as well.
11-11-2007, 04:47 AM
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In my 03 it always locked up when the A/C was on. It also came on when the temps started getting up there. Mine howled pretty loud too.
Yours sounds pretty normal now as long as the truck doesn't start getting hot w/ the A/C on and the fan doesn't lock back up.....
Yours sounds pretty normal now as long as the truck doesn't start getting hot w/ the A/C on and the fan doesn't lock back up.....
11-11-2007, 08:44 AM
#6
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have you read up on clutch fans? if not here is some reading for you
http://www.popularmechanics.com/how_...e/1772922.html
http://www.popularmechanics.com/how_...e/1772922.html
OK, thanks for teh read, will take a look
11-11-2007, 08:45 AM
#7
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Sounds fairly normal to me. I could be wrong...
The fan clutch should engage anytime the AC or defrost is on as the AC Condenser needs extra airflow over it to condense the refrigerant to a liquid for proper AC/defrost operation. If the AC is turned off or the AC pressure switch (or similar signal depending on AC system type) commands the compressor to turn off the fan/fan clutch usually turns off as well. The ECM will also command the clutch to engage/disengage with coolant temp input as well.
The fan clutch should engage anytime the AC or defrost is on as the AC Condenser needs extra airflow over it to condense the refrigerant to a liquid for proper AC/defrost operation. If the AC is turned off or the AC pressure switch (or similar signal depending on AC system type) commands the compressor to turn off the fan/fan clutch usually turns off as well. The ECM will also command the clutch to engage/disengage with coolant temp input as well.
Sounds like mine for sure....but what does YOURS do???? After driving your truck, tell me when YOURS locks and unlocks.
Thanks for the response
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11-11-2007, 08:50 AM
#8
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OK, thanks for leting me know about yours.
This is what I was affraid of.....mine is operating normal now (I believe)
Some how, some way, mine was not doing this before, but now is.
So, now what I am going to do is, get it back to how it WAS before all of this came about. What I did after reading your post was go out and cut my blue wire @ the plug. The blue wire is the main power/feed wire to teh fan. It sends power to the fan when the truck is teh "run" position. What I am hoping is that by doing this, the clutch stays unlocked, and my AC will still work at idle (like it USED to be). And if that works, I a going to install a switch inline of the blue wire I cut, and that way I can toggle teh clutch on and off as I see fit. I just can NOT drive around how my truck is now, that clutch is annoying as heck. SO, I will report back once I find out about the blue wire I cut.
Thnaks for all the replies guys!
11-11-2007, 09:25 AM
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the fan is supposed to turn on when the A/C is on it will help keep the engine cool. Your engine should stay under 200*, with what you are doing would be fine with a gas engine. I had a elec fan W/themastat set a 190* so the fan would turn on at this temp.
As stated before it will turn on when you turn on the A/C regardless of the engine temp.
I bet you never even read about how the fan works.
As stated before it will turn on when you turn on the A/C regardless of the engine temp.
I bet you never even read about how the fan works.
11-11-2007, 09:40 AM
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the fan is supposed to turn on when the A/C is on it will help keep the engine cool. Your engine should stay under 200*, with what you are doing would be fine with a gas engine. I had a elec fan W/themastat set a 190* so the fan would turn on at this temp.
As stated before it will turn on when you turn on the A/C regardless of the engine temp.
I bet you never even read about how the fan works.
As stated before it will turn on when you turn on the A/C regardless of the engine temp.
I bet you never even read about how the fan works.
Well, if it is SUPPOSED to, then why did mine NOT for over 2 years and thousands of miles, and be just fine?????? Only now, that after the wires get ripped out, and I rewire it back up, that it is operating like the factory intended for it to, and it S****
Like I said, there is NO WAY I am going to drive my truck with that clutch locked up with my AC on. And if I can haul a 44' enclosed triple axle grossing 25K+ lbs over 45 states, and NOT have an issue on how it was set up before, it WILL WORK for a diesel (obvioulsy).And you are wrong, I did read up, but I wanted it to hear it from teh horse's mouth, so to speak, the members here on DTR. As, since mine was NOT doing this before my wires got ripped out, and it was SUPPOSED to, then why was mine NOT? Also, since you have only been a member here for a month or so, it is a bit early for you to be making assumptions about me rookie
Now, back to my experiment. I cut the main power line (blue wire @ teh plug) and just did a test run of @ 17 miles, stop and go driving through town......
IT WORKS!!!!!!!! Now, it is too soon to come up with a final conclusion, but so far so good.....AC works @ idle PERFECT....clutch NEVER locked up......temps never got over @ 197-198*. I will put the truck through a more rigourous test this afternoon after football, and if all goes as planned, I will then install my inline switch for the blue wire, and see if I can toggle the clutch fan on and off from inside teh confines of the cab of my truck
11-11-2007, 09:56 AM
#11
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The fan clutch is controled by the ECM. At idle with the A/C on and up to operating temperature the fan will cycle engaging the clutch on and off. It never fully locks. I think there is a thermister in the assembly telling the ECM what temps it sees by varying the voltage. The ECM then interprets when and how to cut on the clutch. Your fan should lock/unlock at idle and completely cut off after you start moving down the road with the A/C on. It seems as though yours got damaged when the wires were ripped out and needs to be replaced. That clutch isn't cheap either. Different year models are programed differently. The new trucks will keep the clutch on longer due to the problem everyone was having with the different temps coming out the vents from left to right. Beemo talked about this in the big A/C thread and I am sure that he had something to do with the programing change in the newer 07' trucks. With that fan on alot I bet it sure sucks down some fuel.
11-11-2007, 09:58 AM
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By cutting the wire there is still a good chance it will run ok but that is partially because there is air flow over the rad and AC condenser while driving...just sometimes not enough under certain conditions which is why the fan clutch will engage with AC or when ECM commands it due to ECT temp. What are the ambient temps outside while you did the 'cut the wire' test? I assume lower then say being in Arizona during July?
I still say there is nothing wrong with the current operation of your fan clutch and it is now working as designed. If it did not work this way before I would say you had a problem before then....but it may be wise to check operation by the service manual incase I am wrong.
The link for how a fan clutch works is wrong for our trucks. It is how an older style viscous fan clutch works. Ours are electronically activated and work more reliably as well as more consistently for given conditions.
11-11-2007, 10:12 AM
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From the Service manual:
The Engine Control Module (ECM) controls the level of engagement of the electronically controlled viscous fan
clutch by monitoring coolant temperature, intake manifold temperature, air conditioning pressure and transmission oil
temperature. Based on cooling requirements, the ECM sends a signal to the viscous fan clutch to increase or
decrease the fan speed.
Fan speed is monitored by the ECM. Fan speeds above or below a calibrated threshold will set a DTC. Circuit
concerns will also set fan clutch DTC’s.
NOTE: It is normal for fan noise to be louder (roaring) when:
² Fan duty cycle high. This may occur when ambient (outside air temperature) is very high.
² Engine loads and temperatures are high such as when towing a trailer.
² Operating conditions where transmission temperatures may be high
² Cool silicone fluid within the fan drive unit is being redistributed back to its normal disengaged (warm) position.
This can occur during the first 15 seconds to one minute after engine start-up on a cold engine.
If the fan assembly free-wheels without drag (the fan
blades will revolve more than five turns when spun by
hand), do not replace the fan drive. This spin test
must be performed when the engine is cool.
If the fan assembly does not free-wheel and a metallic
grinding sound exists, replace the electronically controlled
fan drive (Refer to 7 - COOLING/ENGINE/RADIATOR
FAN - REMOVAL).
NOTE: The following test may take up to 15 minutes
to perform.
The engine should be at normal operating temperature.
1. Set the parking brake and verify the transmission
is in park or neutral.
2. Set air conditioner (if equipped) and blower fan to
OFF.
3. Start and allow engine to reach normal operating
temperatures.
4. Stop engine, connect the scan tool and select
appropriate model year and engine option.
5. Check for and correct existing DTC’s
6. Using Tool 6801, connect pin 1 of the electronically controlled viscous fan drive connector, located at the lower
fan shroud to battery ground.
7. Using the scan tool, verify that DTC 0480 set.
8. Start the engine.
9. Go to the SENSOR screen and observe the fan speed.
10. Run the engine at 2500 rpm.
NOTE: It maybe take 15 minutes before fan speed increases.
11. The fan speed should increase according to the table below.
12. If fan speed does not increase, replace the electronically control viscous fan drive.
13. If the fan speed does increase and there is still a concern, refer to the appropriate Engine Electrical Diagnosis
Section to diagnosis the electronically controlled viscous fan drive control circuit.
CAUTION: If the viscous fan drive is replaced because of mechanical damage, the cooling fan blades
should also be inspected. Inspect for fatigue cracks or chips that could result in excessive vibration.
Replace fan blade assembly if any of these conditions are found.
clutch by monitoring coolant temperature, intake manifold temperature, air conditioning pressure and transmission oil
temperature. Based on cooling requirements, the ECM sends a signal to the viscous fan clutch to increase or
decrease the fan speed.
Fan speed is monitored by the ECM. Fan speeds above or below a calibrated threshold will set a DTC. Circuit
concerns will also set fan clutch DTC’s.
NOTE: It is normal for fan noise to be louder (roaring) when:
² Fan duty cycle high. This may occur when ambient (outside air temperature) is very high.
² Engine loads and temperatures are high such as when towing a trailer.
² Operating conditions where transmission temperatures may be high
² Cool silicone fluid within the fan drive unit is being redistributed back to its normal disengaged (warm) position.
This can occur during the first 15 seconds to one minute after engine start-up on a cold engine.
If the fan assembly free-wheels without drag (the fan
blades will revolve more than five turns when spun by
hand), do not replace the fan drive. This spin test
must be performed when the engine is cool.
If the fan assembly does not free-wheel and a metallic
grinding sound exists, replace the electronically controlled
fan drive (Refer to 7 - COOLING/ENGINE/RADIATOR
FAN - REMOVAL).
NOTE: The following test may take up to 15 minutes
to perform.
The engine should be at normal operating temperature.
1. Set the parking brake and verify the transmission
is in park or neutral.
2. Set air conditioner (if equipped) and blower fan to
OFF.
3. Start and allow engine to reach normal operating
temperatures.
4. Stop engine, connect the scan tool and select
appropriate model year and engine option.
5. Check for and correct existing DTC’s
6. Using Tool 6801, connect pin 1 of the electronically controlled viscous fan drive connector, located at the lower
fan shroud to battery ground.
7. Using the scan tool, verify that DTC 0480 set.
8. Start the engine.
9. Go to the SENSOR screen and observe the fan speed.
10. Run the engine at 2500 rpm.
NOTE: It maybe take 15 minutes before fan speed increases.
11. The fan speed should increase according to the table below.
12. If fan speed does not increase, replace the electronically control viscous fan drive.
13. If the fan speed does increase and there is still a concern, refer to the appropriate Engine Electrical Diagnosis
Section to diagnosis the electronically controlled viscous fan drive control circuit.
CAUTION: If the viscous fan drive is replaced because of mechanical damage, the cooling fan blades
should also be inspected. Inspect for fatigue cracks or chips that could result in excessive vibration.
Replace fan blade assembly if any of these conditions are found.
11-11-2007, 10:12 AM
#14
Registered User
Sounds fairly normal to me. I could be wrong...
The fan clutch should engage anytime the AC or defrost is on as the AC Condenser needs extra airflow over it to condense the refrigerant to a liquid for proper AC/defrost operation. If the AC is turned off or the AC pressure switch (or similar signal depending on AC system type) commands the compressor to turn off the fan/fan clutch usually turns off as well. The ECM will also command the clutch to engage/disengage with coolant temp input as well.
The fan clutch should engage anytime the AC or defrost is on as the AC Condenser needs extra airflow over it to condense the refrigerant to a liquid for proper AC/defrost operation. If the AC is turned off or the AC pressure switch (or similar signal depending on AC system type) commands the compressor to turn off the fan/fan clutch usually turns off as well. The ECM will also command the clutch to engage/disengage with coolant temp input as well.