Clutch Fan

35

Asked by Oct 25, 2015 at 03:02 PM about the 2004 Chevrolet TrailBlazer LS 4WD

Question type: Maintenance & Repair

My clutch fan was engaged at idle and running fast. However I did not see any check engines to indicate a bad clutch fan. I checked the relay and fuse, I also checked there was power going to the plug and there was. It made sense it was the clutch fan so I installed a new one but it is still running fast at idle. Do I need to reset something to get it to run properly?

28 Answers

7,740

Whatsa clutch fan? If you mean the fan on the radiator --that's electric and it's controlled by the engines temperature ~ in fact some fans continue running after the engine is off

1 out of 1 people think this is helpful.
35

i have an electric clutch fan not electric fan, it is engaged all the time at idle so it sounds like a jet engine. I installed a new clutch fan but it is still roars at idle. I checked the relay the fuse and there is power going to the plug for the clutch fan. Could a partial closed thermostat cause the problem?

2 out of 2 people think this is helpful.
51,825

Tom & I are confused on what you are asking, a clutch fan is on the fan itself that is mounted onto the water pump & run by the serpentine belt , and is operated by temperature, it spins continuously with the fan, no electric wires, no relay or fuses. The clutch fan will kick in more at an idle, and roar, because of the heat built up in the engine compartment produced by the radiator & the engine,

1 out of 1 people think this is helpful.
7,740

If you tell us what you bought ,,Name, Part number etc we can research what you are describing

35

This what I bought: Dorman® 622-001 - Electronic Radiator Fan Clutch This is an eclectic clutch fan and you have to plug it in. This is for my 2004 Chevy Trailblazer LS. I installed a new electric clutch fan because the other one was operating on high even when the engine was at idle. But once I installed the new one it is still operating on high at idle.

7,740

Nice unit ... This unit is activated (of course) by the coolant temperature sensor and will run regardless of engine speed. .. in fact it's normal for a fan to run at idle if the engine sensor is triggered. You are trying to fix the results of a problem but you need to find the problem. What temperature is your engine running at ,,, and does the fan ever go off ? Do you live in a hot part of the country? Does the fan come on when the car is first started (when engine is cold) ?

35

The fan does run at engine speed but it is running to fast at idle. When you are on the road it almost feels like you are pulling a boat. When I get to highway speeds it does feels like it disengages. The temperature is normal. The fan never goes off. I have no check engine lights. You are right about trying to fix the problem which I thought I did. Something else is causing the fan to engage on high at idle.

7,740

Please answer ... when the engine is cold .. does the fan come on when you turn the key on (no start) ? Does the fan come on as soon as you start engine (engine still cold) ? My research says this is where the temp sensor is located ... let me know if this is your engine

1 out of 1 people think this is helpful.
7,740

or this

35

When the engine is cold .. does the fan come on when you turn the key on (no start) ? Ans: The fan does not come on when I turn the key on (no start). Does the fan come on as soon as you start engine (engine still cold) ? Ans: yes the fan comes on fast and stays that way even after a few minutes. The pictures you sent is where the temp sensor is located. I noticed that when I disconnected the temp sensor the fan ran even faster like a jet engine. I have not tested the temp sensor. I was going to do an ohms test to see if it was bad. Can the temp sensor go bad half-way and make the fan run faster than it should?

7,740

Sensors bad... it's called a "thermistor" A device whose resistance changes with heat. When the engine is cold it's reading is very low to ground ... as it gets hotter the resistance changes ... removing the connection caused the computer to send full voltage ,,, if you put about a 100ohm resistor on that wire and touch the resistor to ground the motor will not come on ... that proves you need a new sensor

7,740

Thermistors range goes from about 100 ohms cold to about 10k hot

7,740

I'll bet that if you put a meter on the probe to ground (with the wire disconnected) you will read well over 1000 ohms

35

So when checking the resistance and I put both leads onto the plug and I got no readings cold on the meter. I let the engine warm up to operating temperature and did another reading and got about 470 ohms hot. So I guess I have a bad temp sensor? Also I noticed that the temp gauge still works so it is still taking temperature readings.

1 out of 1 people think this is helpful.
7,740

No reading or infinity should cause the fan to reach "Take-off speed" and 470 ohms should make the fan run slower. I would say the Pickup is bad and I donno why you still get a temp reading but we are only interested in the pickup for the fan. Take your meter to the dealer (or salvage yard) and see what a normal cold reading is

35

I removed the sensor and did another reading and cold it was 2900 and I put it in hot water and it gave me 400 ohms. I don't think I had it on the right setting when i was testing it cold. I will go to the parts store and compare a new one.

51,825

I have a chart on temp. sensor test readings, it says at 70* you should be looking at 3400Ω, & at 200* you should be at 225Ω

51,825

Interesting fan clutch, that is what I was describing, but never came across one of those...

7,740

Hmm // so the higher the reading the lower the fan speed or visa-versa .. but when the wire was removed it went balls to the wall. I would be curious regarding a 400 ohm to ground and a 4000 ohm to ground speed change (I'm assuming the speed is referenced to ground and not 12VDC)

51,825

resistance (ohms) regulates the amount of voltage,

51,825

I should add that a temp. sending unit is the base cause for problems that is over looked. All other sensors rely on what it is telling them to do. You could be running rich and think it is caused by another sensor, when it is not.

7,740

The sensor input is computed by the ECU (floating decimal) that assigns a range (probably 20% >>> 100% of fan speed) based on a range of 4000 >>> 400 ohm input that's converted to MilliVolt input >>> but what bothers me is at High resistance (cold engine) the fan is at high speed -- not off or low speed.so it seems as though the signal is inverted ...however the assumption still remains that a change in resistance changes fan speed ... this can be proven by using 2 resistors and determining if the speed does change and does the change go in the direction we should see when the engine gets hot (sorry I'm an engineer and I can't help "making a mountain from a mole-hill"

7,740

But if the input is referenced from +12 VDC that would invert the output

51,825

So wires crossed? Hooked on a constant 12V supply?

51,825

How about this theory which I know part of it is true being I know the temp. sender can still show temp. on the gage, but if the resistance side is bad but then would send the 12V to the fans? Should you have him check voltage at the power fan wire?

7,740

At this point I would call the fan manufacturer and ask his advice because for all we know they have encountered this problem before. They deal with thousands of people where this is a learning curve for us. I FOLLOW THE HIPPOCRATIC OATH "DO NO HARM"

1 out of 1 people think this is helpful.
51,825

Say there Tom, I like that oath also, but some times I say "no balls no glory"

Where exactly is the sensor for the electric fan clutch for the radiator on my 2002 Chevy trail blazer

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