Cooling Fan Clutch

I have had an ongoing issue with my AC getting warmer when idling. Sometimes almost the same as the outside air temp. While driving it stays decently cool. I took a look at my fan clutch and it seems the clutch resistance stays the same regardless of temperature. Is the clutch fan bad? And could this be part of the reason behind the AC issue? Also, fuel mileage is worse than it should be... also linked to a bad fan clutch?

 

I have the same issue, as it appears, many do. The fan clutch is supposed to kick in at about 170 degrees at idle. I suppose you can tell if it's bad by measuring the fan rpm speed before and after it engages. Laser non-contact rpm readers are as low as $18 on Amzn.
I cleaned the condenser fan with spray-on foam, but that didn't help at all. The only solution I've seen is installing a pusher fan over the condenser. I'll find out if replacing the fan clutch helps when I replace it at 200K miles when I plan on also replacing the radiator and water pump as preventive maintenance. I'm at 185K now, so I'm about two years away from that.

 

The AC in these trucks is adequate at best.
Anything close to 90+ degree and at an idle is much “worse”.
If you search the forum, you’ll see you aren’t the first one to complain of the same symptoms.

I’d probably have the AC coolant levels checked.
It’s normal for them to leak down over many years. After all, your truck is a 2008.
So you are almost 13 years on factory fill.

As for the Fan Clutch.
The post #10 and #19 here.
https://www.tacomaworld.com/threads/overheating-at-low-rpm-thoughts.674697/

 

That thread has to do with overheating at low rpm. The OP did not report overheating issues, and neither have I. If AC blows cold when the car is moving, but not at idle, that kinda points to the problem not being related to low freon. Mine was low five years ago and it took half a can to refill/recharge the system. Yet, the low cold at idle issue remains. It blows ice cold at speed, but not a idle.

 

OP asked about the fan clutch.
The link gives brief ideas of how to check it.

As for the AC issue, I haven’t seen a definitive answer on a permanent fix.
Google search will reveal its fairly common.
You can read through them and see if anyone has a fix.
I haven’t seen or heard of a fix for “poor cooling at idle” yet.
Not saying there isn’t one, but the majority of the fixes involve cleaning the condenser and making sure the cooling system is full on refrigerant.

 

That's where I got the clean-the-condenser idea. But, didn't perceive any progress. If replacing the fan clutch don't help, installing a push through electric fan may be the best fix. I think a new condenser may be the best fix, but that gonna be an expensive fix.

 

Yeah, I’m sure it will be expensive.
And I don’t know enough about AC systems to do it myself.

I don’t like touching Automatic Transmissions, AC, or or differential gear sets.
Those are jobs, I’ll have to pay someone else to do.

 

How to check the cooling system silicon clutch:

https://www.aa1car.com/library/cooling_fan_clutch.htm

FAN CLUTCH OPERATION


The clutch consists of a fluid coupling filled with a silicone based oil. In the cutaway view at the left, the area between the teeth on the clutch plates is filled with silicone fluid. An internal valve opens and closes a passage between the main fluid cavity and a fluid reservoir. When the passage is open, fluid enters the clutch and makes the fan to turn faster. When the valve is shut, fluid flows back to the reservoir but doesn't return, causing the clutch to slip and the fan to turn more slowly.

The non-thermal (torque limiting) fan clutch doesn't have a temperature sensing capability. It reacts only to speed, slipping to limit maximum fan speed to about 1200 to 2200 rpm depending on the application.

FAN CLUTCH PROBLEMS
A slipping fan clutch is often overlooked as the cause of an engine overheating problem.

As a fan clutch ages, fluid deterioration gradually causes an increase in slippage (about 200 rpm per year). After a number of years of service, the clutch may slip so badly that the fan can't keep up with the cooling needs of the engine and the engine overheats. At this point, replacement is often necessary.

Other signs of fan cluch failure would include any looseness in the clutch (check for fan wobble), or oil streaks radiating outward from the clutch hub.

If the clutch is binding, the fan may not release causing excessive cooling and noise, especially at highway speeds



CHECKING THE FAN CLUTCH
A good clutch should offer a certain amount of resistance when spun by hand (engine off, of course!). But if the fan spins with little resistance (more than 1 to 1-1/2 turns), the fan clutch is slipping too much and needs to be replaced.

If the fan binds, does not turn or offers a lot of resistance, it has seized and also needs to be replaced.

Fan speed can also be checked with an optical tachometer, by marking one of the fan blades with chalk and using a timing light to observe speed changes, and/or listening for changes in fan noise as engine speed changes.

You should also try to wiggle the fan blades by hand. If there is any wobble in the fan, there is a bad bearing in the fan clutch, or a worn bearing on the water pump shaft. A bad water pump bearing will usually cause the water pump to leak and/or make noise, but not always. Remove the fan clutch and see if the play is in the water pump shaft. If it feels tight (no play or wobble), replace the fan clutch.

 

There is a TSB for cooling at idle and high temps for some 2015s. I wonder whether this TSB and kit would help much?
T-SB-0034-18.pdf

 

thanks for the responses. I feel like if the fan clutch is bad i would have engine overheating issues, which i do not. As far as AC refrigerant goes, it has been all purged and recharged while replacing the AC compressor with a brand new one (separate issue). While driving i will see temps out of the middle duct of about 49-50 degrees, with an OAT of about 80. I have yet to measure the temp on a really hot day, as i live in VT and those days arent as common. But with outside temps over 90 the truck has a hard time cooling down inside even while driving. Condensor issue maybe?

 

Fan clutches can gradually go bad. Still enough air to cool the radiator but not enough air to cool the condenser. Manifold gauge readings would help a lot with diagnosis.

I'd put in a new clutch. Not expensive, and not hard to R&R.

 

yeah I've been thinking about it. Might be worth a try. Just no other indications that its bad...

 

Have you done the diagnostic steps @Jimmyh posted?

Fan clutches of this style have been around since the '60's. Pretty simple to physically test, as described in his post.

Another free step is the space between the condenser and radiator may be packed with stuff. And not easy to see from the front. Loosening the radiator and laying it back just a bit will give a better angle to wash out that area.

 

yeah, there is the same amount of resistance on the clutch no matter cold or hot. it won't spin freely but it definitely doesn't bind, and there doesn't seem to be any play in bearing. Planning on cleaning the condenser and radiator thoroughly tomorrow, as well as the space in-between. it doesn't appear to be too bad but will post an update tomorrow.

 

Update.. I cleaned both condenser and radiator as best I could, also replaced the fan clutch as it was quick and easy. Seams to be very little if ANY difference in vent temps. While driving around with an OAT of 85, I was lucky to see 52-54 degrees. While parked goes up to 58-60. Only other thing I could see replacing would be the condenser... but not entirely convinced it will make a difference. That being said, the old fan clutch will probably go back on, and I'm back to square one.

 

Then it's faulty.

Curious what brand of fan clutch you used? New doesn't always equal good.

I went through a similar fan clutch issue with my XJ a couple years back, and turned out that five fan clutches in a row were defective (all of them good aftermarket brands). Bought a new one from Jeep, problem solved. If you went aftermarket, try one from Toyota or specifically Aisin brand as that's the OE supplier.

Also, what is the humidity when it's 85°F out and you're getting 52/54 and 58/60 from the vents? What are the operating pressures from the A/C when this is happening? All of this plays a role in A/C performance. Don't shotgun anymore parts at it until you actually diagnose an issue, otherwise you're just needlessly spending money.

And not to be a Debbie-downer, but the old industry rule of thumb was always if vent temps were 30° less than ambient on a given day, that was considered acceptable if temperature/humidity and operating pressures were all relative. If it's 85 outside and you're getting 58-60 from the vents a hot idle, it's not great but not terrible considering your original complaint was vent temps coming up/almost matching ambient. Remember, "air conditioning" is doing exactly that; it doesn't create cold, it removes heat.

 

It's an aftermarket fan clutch from NAPA.
The new one acts the same as the one I took out. Fairly certain the old one is fine, but it was worth a shot.

On my drive from work just now, the lowest I read was just a hair over 60 degrees. It's currently 87 and 48% humidity. I don't know what the pressure readings are as I don't have a set of guages. I won't be tossing any more parts in until I find a problem, however there is no one in my area I really trust with AC work. I'll probably grab a set of guages just to see what I'm reading, as well as check temps on the condenser for sign of any blockage.

This is the second summer with this issue and had a couple people look at it last year and they offered zero help.

 

Sounds like the fan clutch was not bad. You don't have a manifold so no readings.

Square one. Empty the system, pull a good vac then weigh in 22ozs R134A. Report back with vent temps, ambient temp and humidity.

 

I evacuated the system (pulled a vacuum for around an hour). Put in 22oz of 134A. today was a cool day 60F, but my high-pressure number seems lower than it should be. About 130PSI HP and 26PSI LP. I put a gauge on it before doing all this and the numbers were 145PSI HP and 20PSI LP, which also is on the lowish side.

Everything seems to be cycling fine, and the vent temp was sitting at about 45F at idle but an ambient temp of only 60F and humidity <40%.

Tough to tell if anything has changed temperature-wise until we get warmer temps here. If vent temps stay <50F I would be happy.

Edit: would like to add, the cycle time of the compressor is pretty short, maybe 15-20 seconds on and off. Is that normal or should it be longer than that?

 

60f ambient is too cool to go by gauge readings. You did the right thing by pulling a vac and weighing in the charge. Wait for a hot day, check the vent temp, and be happy with what you get. Don't look for a problem that doesn't exist.