Darryl&Rita

Pulling with the truck, on holidays and all, if the speed comes down on a hill, the temps go up. WAY up. No code is being set, all I'm seeing is 4 or 5 dashes, followed by donE. I have heard the fan on 2 separate mornings, pulling out of campgrounds, but with the hood lifted on the side of the road, there was no "roar", and barely any air pulling through the rad. The temp gauge was near the "OH NO" end while standing there listening. Is it possible for these things to get weak, or is this how they fail. I tried to get it to fire one evening with a blanket on the rad, but couldn't get the temps up much just idling.

C Schomer

I had the same problem last camping trip - high heat but no fan roar. I got a new stat and put it and the old one in water on the stove. The new one opened 1 1/2 times as far as the old one. I'll know in a few weeks if that fixed it. Also cleaned out all the bugs in the front, which wasn't bad at all, and replaced the belt. The fan can't sense the heat if it doesn't get out of the engine. Craig

papaduck

Check the wires to the fan that are attached to the back of the radiator to make sure they are not cut by the fan. The fan should engage when the A/C is on.

Not sure but I think the engine temp and not the temp of the air over the fan clutch is what causes the fan to be engaged.

01Turbo

I thought the fan clutch was hydraulic? Aren't the wires coming from the fan clutch just for telling the ECU whether the fan clutch is engaged or not at any given time?

01Turbo

tryNto

Found this online...

OK. Below is a description of the Electro viscous fan clutch. It differs from a standard fan clutch simply by the control. The standard clutch uses a thermostat on the front side to rotate a small shaft which increases the fan speed depending on the heat coming from the radiator.

The ECM controls the Electro-viscous fan clutch engagement. The control module regulates a 12-volt pulse width modulated signal (PWM) to the cooling fan relay. The PWM signal determines the ON time of the relay. As the commanded state of the fan clutch increases, so does the ON time of the relay. This ON time directly effects the amount of time the solenoid, which is internal to the fan clutch, is energized. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, increasing the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and blocks the path of the fluid to the fluid coupling of the fan clutch, reducing fan speed.

The fan has the ability to create a feedback signal, so the control module has an actual fan speed input. This is done with a Hall effect sensor internal to the fan clutch. The control module supplies a 5-volt reference and a low reference to the Hall effect sensor. The Hall effect sensor returns a signal pulse through the cooling fan speed signal circuit in response to the reluctor track passing by the magnetic field of the hall effect sensor.

Diagnosis of both fan clutches is similar for the mechanical aspect. If there is any lateral movement in the drive, then the clutch is in need of replacement.

The standard fan clutch will typically spin abnormally free when it fails, and should spin with some resistance normally.

The Electro-viscous clutch being electrically controlled had DTC's that will set if the speed is not what is commanded or there are open circuits to the sensors.

Leaks on either unit indicate failure of the clutch.

HUNTINNUT

The standard fan clutch will typically spin abnormally free when it fails, and should spin with some resistance normally.

thats the most info i have seen on how it works.
i am having the opposite problem, mine is running to often, even when first started and air is on. i know its going to run when ac comp. is engaged but it sounds like it runs the same as eng revs. i cannot spin my fan as stated above, maybe 1/4 turn at most. how many turns can you all spin your fan when cold?

01Turbo

Well I can't figure out why I have no issues with my truck right now then. The wires coming off of the fan clutch are currently severed and have been since I bought the truck 1 month ago(just haven't got around to replacing yet), but yet I don't have any check engine lights on and have no overheating issues and no fan running constantly...so why am I not having issues???

01Turbo

DiezelSmoke

You live in Canada, go to Texas and you may have a problem. The coolant system on these trucks have a large cooling capacity unless your pulling it could do with about half. Mine was also cut and I never new it until I went to use the A/C and the ECM locked out the A/C. The dealer said it needed a new fan, I brought it home and fixed the wiring and works good now. There is a cutout in the fan shroud for the wire to sit in, I recomend drilling a 1/4 hole on each side and ty straping the wire into the notch to prevent this again.

01Turbo

Thanks alot for the info...I was also told there was no way to fix the wires, only way was a NEW fan clutch unit(fair chunk of cash). So you we able to basically splice the wires back together?

01Turbo

DiezelSmoke

You can splice them it is PITA the best is to take the fan hub out and do it. It takes a 33mm thin wrench, order the fan hub set from Harbor Freight. Also use heat shrink type connectors.

rogers259

Couldnt find a 33mm wrench and didnt have a Harbor Freight around...closest thing I could find was a 32mm wrench at Tractor Supply. Ground it open to 33mm and it worked like a charm.

Its alot easier to take off the fan clutch and put it back on with two people. That sucker is on there tight! Do some searching around and you'll find the best price on a fan clutch.

Darryl&Rita

Just did some quick testing:
1. Truck just started, A/C off-normal sheet of typing paper will not stick to condensor with fan suction.
2. Truck still cold, A/C on-no change in sound, paper will not hold.
3. Truck up to temp, A/C on or off- no change in sound, paper will barely hold to condensor.
Looks like I'll be changing a fan clutch, huh?

tryNto

http://www.rockauto.com/ has a good price on them...

DiezelSmoke

If your wires are cut the fan won't work! Are they cut?

Darryl&Rita

Wires look OK, and no codes set.