Air Conditioning question - I suspect a clogged condenser

Got a AC question. I've noticed my AC cuts out after I've been idling for a while. AC isn't super cold to begin with, but if the truck idles for 30 minutes or so it cuts out completely, but works when the truck starts driving again.

When the AC works, the low port reads 45 PSI, compressor is obviously engaged. When the AC cuts out, it reads about 110 PSI. The fan engine fan is spinning the whole time, but under hood temperatures seem awfully hot and the condenser is hot to touch. The compressor is no longer engaging. The engine temperature gauge is about 2/3 of the way up, so nothing abnormal.

I have not taken a high port reading yet.

Obviously I need to get a high port reading while the AC is running, but has anyone else experienced this problem and what was your solution?

 

Going to add: the faster I drive the cooler the AC is.

 

Pop your hood and see, with the engine off, if you can spin the fan clutch easily by hand.

 

Will give it a try in the morning.

 

45psi while running is pretty high.
Have you opened the system for recharge anytime recently?
Take a hose to the condenser and give her a nice bath

 

I was thinking it was a bit high, and why I thought it might be clogged. I'll hose it off in the morning. Doesn't look like a lot of debris though.

I've just had this truck for a month and am still learning it.

 

Been seeing a lot of this lately, and yes you have a clogged up condenser. Don't use high pressure as it can damage the fins.

 

Thankfully our condensers are somewhat robust, not like your standard home AC where you look at them wrong and the fold!
But yeah don’t use a needle point pressure washer to do it. I usually do a open ended hose on full blast and sometimes use my thumb, mainly for angle of the dangle trying to get certain parts not easily hit straight on

 

The AC pressures will rise from the inadequate airflow over the condenser and excess heat in general. So definitely hose out the condenser, but check that fan clutch as well.

The fact that your A/C cools down while driving, indicates the condenser is getting at least some air flow through it while driving.

 

It depends what the ambient temp was when he was seeing 45 psi. It's been smoking hot where I am lately

 

He said it was running and at 45psig, those are ambient temps to static pressures with the system off.
Edit, I guess those aren’t static pressures, but still that chart is terrible.

 

45psi means a 50 degree evap coil give or take

 

It’s always been my understanding to run the manifold gauges on a running truck, with the compressor cycling.

Regardless OP, if you get the the point you’re troubleshooting with manifold gauges, here’s a little general cheat sheet to look at.

 

https://www.youtube.com/watch?v=G-tCIRJH9p0

 

My first thought is fan clutch. Running colder while moving shows the AC is working....but its having trouble getting rid of heat.

With the engine hot, turn it off and then try to move the fan by hand. It should not be able to move without turning over the engine.

 

Even my new clutch wouldn’t turn the engine over

 

Well, looks like there is some variation then. Mine may as well be bolted to the crankshaft when its hot.

Either way, check it. The fan should at least be much harder to turn while hot.

 

So with my engine cold this morning, the engine fan was easy to spin by hand. After I drove to work (15 minute drive) it was still easy to spin by hand. This afternoon I'll be sitting in a parking lot again for about 40 minutes (this is when the AC cuts out), I will check to see if the fan is easy to spin by hand if / when it cuts out. My truck's thermometer registered 103 degrees yesterday when I took a pressure reading on the low port and got 45psi.

I did hose off the condenser this morning. Didn't seem like a lot was stuck on it, just a few bugs.

 

There should be at least some resistance at all times on the fan clutch. At least enough to keep it from freewheeling when you spin it and let go. Sounds like that may be the culprit. Fingers crossed!

 

How much resistance should there be? There is some, but not alot.

 

According to Google: “If the fan rotates more than five times, you can bet the clutch is bad. You should feel some resistance and the fan may spin up to three times, depending on the ambient temperature. But even if it rotates three or fewer times the clutch could still be bad.”

So I guess it varies.

How many miles are on the truck? And what does the fan clutch run? It’s quick job.

 

The fan doesn't rotate freely, I can move it easily with my hand, but the moment I take my hand off it it stops. I would say it takes 3 or 4 pounds of pressure to move it.

207k miles. Probably time for a clutch anyway. I've had the truck for a month, no idea how long the current clutch has been on there.

 

AC just cut out. Fan still doesn't spin freely but can easily be moved by hand.

 

So here is what I think is happening.

I think the fan clutch is bad, causing the pressures in the AC system to rise at idle, due to no air/inadequate air flowing through the condenser and then eventually causing the system to shut off due to high pressure at the high pressure cut off switch.

 

Mine won't spin freely when cold, but moves easily, 3-4 lbs of force sounds about right.

When hot, I don't think I could move it without turning over the engine. At least 30lbs of resistance.....I've never tried to press harder as I'm afraid I'd break a fan blade pushing too hard.

If you aren't feeling at least a SIGNIFICANT difference between a hot and cold engine fan, its your clutch for sure.

And as mentioned, this would explain your AC problems. AC only works if it can shed heat and cause enough pressure difference to cycle (literally, cool enough to cause the condenser, to condense) If it can't remove heat fast enough, it simply stops working.

 

I do think you all are onto something with the fan clutch. There is no difference at all in resistance between hot and cold on the fan clutch. Would make sense, as the fan still spins but at a lower than optimal RPM. If it can't shed heat, temps rise and AC cuts out until I start driving again and air naturally starts circulating again.

I'll get a fan clutch on order. Thanks for your help!

 

No problem! Keep us posted!

 

Exact information I was looking for! Thanks!

 

It’s not a bad job, might want to think about 4 new bolts, I rounded mine pretty good getting them off. You can remove the lower radiator shroud and slip a piece of cardboard over the rad to protect it, just in case moments.

 

Believe me, I am relieved it's just 4 bolt bolts. Looks a bit easier to do than on my old Dodge where I had to somehow keep the water pump pulley still while removing the fan clutch nut.