Why is my air conditioner weak?

Agreed, I need to find that out. What is the proper name of that machine? Snap-on just called them "AC Machines".

https://b2b.snapon.com/productDetails/927472/2/881820

 

It's just an "a/c service machine"

Ours are made by RobinAir

Its not uncommon for the machine to come up short on the charge too, like if the source tank was partially empty or somebody was in a hurry and pulled the machine off too soon

 

I'm thinking the truck needs to go back on the machine regardless. I'm dropping it off Sunday evening. Always fun.

I hate tasking shops with finding intermittent problems.

 

I had a Ranger a few years ago. The A/C would only blow cold when the engine was revving and/or moving forward at a reasonable speed. Like you, I noticed the fan clutch was louder at initial startup, but quieted down. Read that the viscous fluid can "wear" or seep over time so tried a new clutch (did not replace the fan blade). Worked great. Note that in my case, it also seemed that the ENGINE cooling system seemed a little high in city traffic as well (though not overheating), which is why I decided to go the fan clutch route.

Here's an explanation of why/how:

https://youtu.be/vFePKBuE024?si=or0EeDpl_W293yJQ

 

Interesting, thanks.

I might have them replace the fan clutch. It shouldn't be doing what it's doing.

I've been keeping an eye on the coolant temperature gauge lately. It seems maybe ever so slightly higher than normal, but nothing alarming.

 

Auto AC systems will ALWAYS weep a little around the compressor seal. It does this by design to keep that seal moist. I get my AC evacuated and refilled about every 5 years. It’s 16 years old and will still freeze you out even if over 100 outside. Now when idling for a long time, it’s not as cold since the AC pressure isn’t up and not as much air is flowing over the heat exchanger. That’s normal.

 

Spray the condenser with a garden hose while the truck is idling in the driveway, that helps with the heat transfer through the fins and can help identify a bad condenser

The reason a lot of trucks blow colder while moving down the road is not just because of the extra air flow across the condenser, but because the engine is spinning faster, so the compressor is spinning faster and moving more refrigerant through the system.

Heat transfer at the condenser is critical because if the system can't give up heat to the atmosphere it can't generate cold air inside the cabin. That's how AC systems work. It absorbs heat from the cabin moves it to the front of the vehicle and gives it up to the air flowing over the front of the car.

 

That was in fact what I was alluding to, fan clutches do wear over time and it's amazing the difference it makes when you replace them at high mileage.

However the proper charge is paramount.

In the absence of being able to verify either by weighing it or at the least throwing on a set of gauges, the last check I can think of from outside the system is to see if your clutch coil is weak/ clutch air gap too big. The safe way to check that is to backprobe a test lamp of some sort( a plate bulb, headlight bulb, or any other incandescent test light will work) into the clutch connector and go for a spin. When the A/c cuts out, pop the hood and see if the light is lit but clutch not engaged and spinning.... the dangerous way is to go for the same spin and pop the hood when the a/c cuts out and look for the hub to be spinning, if it's not then tap on an edge with a screwdriver or something while everything is turned on still and see if it pulls in and starts working again.... if you try the dangerous way then tap a side where if the clutch were to engage and grab the screwdriver it wouldn't send it somewhere bad.

 

If that were the case the a/c light would be flashing

There's a lock sensor on the compressor that watches the rpm of the compressor shaft. If the ac button is commanded "on" and it doesnt see a rpm signal it will make the light flash

Long story short, if he's not seeing a flashing light then the compressor is running when it's supposed to

 

Interesting and thank you. I'd heard about that on the 3rd gens but didn't know the 2nd gens were like that too

 

most of my experience is with 2nd gen and those are mounted on the outside of the compressor case. I believe 3rd gen is mounted inside? But the idea is the same. A feedback signal to tell the controller the compressor is actually spinning

If the system is happy enough to engage the mag clutch relay in the fuse box (a/c button on, pressure switches ok, etc).. it expects the compressor to be spinning. So everything "downstream" of the relay is monitored by that lock sensor

 

My A/C machine is a tank of R134a sitting on a bathroom scale.