Automotive Air Conditioning Information Forum

It means airflow over the condenser is compromised. Water conducts heat waaay better than air, which is the reason for the test.
Check your electric fans if any. I have replaced weak ones before. Check your fan clutch. They typically 'wear out' in 3-4 years. The car engine itself will not necessarily overheat, in fact, seldom does, but the airflow over the condenser can easily be compromised.

Is there one electric fan or two? Are they 2-stage fans?
Perhaps one is not working. Perhaps they are not kicking into high speed.
When I rig up a custom system, if the comp is on, then the condenser fan is on at all times, period

DBBAir wrote: ↑Tue May 17, 2022 1:22 pm Air temp: 79 Humidity <20%
at idle: 36 on low side, 225 on high side, temps about 40 and greater
at 1800RPM: 30 on low side, 220 on high side, temp about 38 and greater
Misting at 1800 RPM: 30 on low side, 160 on high side, temps 38 and greater

220 psi, not sure why an issue is being raised about high pressure.

The pressures at idle don't tell us much. But at 1,800 RPM, the LP at 30 PSI is just right and the HP at 220 PSI isn't high, although at 79 degrees ambient, it could be a bit lower--around 180 to 190 PSI. The misting test tells us that the condenser is working but that airflow could be a little better across it.

Check the condenser core for any dirt or debris build-up that might be partially blocking airflow. If it just looks dirty overall with obvious crud between the fins, a careful spraying with a heavy-duty detergent and rinsing with a gentle stream of water could be beneficial, especially if it's the original condenser in which grime has had a chance to build up over the years. Go at it gently because you don't want to deform the fragile metal fins, which water from a garden-hose nozzle or a stiff bristle brush can do. Likewise, don't use a pressure washer.

Also check the fan, either viscous drive or electric, and ensure it's running at a good clip with the engine at 1,800 RPM and warmed up.

Other than cleaning the condenser, and based on the newer set of pressures you posted, it now sounds like the refrigerant amount is within specs. So I would leave the refrigeration part of it alone, as Tim mentioned.

At 80 degrees ambient. You're hardly in an optimal temp range to perform diagnostics. Posted readings are not far off. Again, I would do nothing until it is warmer out. But that's just me.

tbirdtbird wrote: ↑Tue May 17, 2022 2:01 pm Check your fan clutch. They typically 'wear out' in 3-4 years.

I have a continuously variable fan clutch. Do they wear out in 3-4 years or just electric fans?

JohnHere wrote: ↑Tue May 17, 2022 2:39 pm If it just looks dirty overall with obvious crud between the fins, a careful spraying with a heavy-duty detergent and rinsing with a gentle stream of water could be beneficial, especially if it's the original condenser in which grime has had a chance to build up over the years

Will do

Also check the fan, either viscous drive or electric, and ensure it's running at a good clip with the engine at 1,800 RPM and warmed up.

It is viscous drive and seems to be working at 1800RPM. There is a tech bulletin that indicates the fan gets pretty noisy when 2nd stage kicks in. Mine certainly is like that - it roars.

Tim wrote: ↑Tue May 17, 2022 2:06 pm
220 psi, not sure why an issue is being raised about high pressure.

That's my question!

Thanks

You originally posted that your high side was 250. And that the cooling had changed from what you were used to. That info is what we responded to.
Also, JohnHere asked what the ambient was when you first got the hi side of 250, but an answer was not forthcoming.

tbirdtbird wrote: ↑Tue May 17, 2022 5:59 pm JohnHere asked what the ambient was when you first got the hi side of 250

Yeah "the temperatures were about 78-80 with less than 20% humidity."

So, I sprayed heavy duty degreaser on the parts that I could see from the front and rinsed it off. After I believe it had ample time to dry out, the readings were:

Low 28
High 175
Active clutching on and off
Temp inside 38
Ambient temp 80, <20% humidity

Can't say that it looked like I clean much out, but it looks like that could have done it. My mind is clear and I can go on the trip without worrying about that issue - at least until the next issue arises!

Thank you all so much for the help and your time. I really appreciate it.

Doug

DBBAir wrote: ↑Tue May 17, 2022 6:41 pm

tbirdtbird wrote: ↑Tue May 17, 2022 5:59 pm JohnHere asked what the ambient was when you first got the hi side of 250

Yeah "the temperatures were about 78-80 with less than 20% humidity."

So, I sprayed heavy duty degreaser on the parts that I could see from the front and rinsed it off. After I believe it had ample time to dry out, the readings were:

Low 28
High 175
Active clutching on and off
Temp inside 38
Ambient temp 80, <20% humidity

I would definitively say your readings are much improved.
Remember, the first word in Air Conditioning is AIR.
The condenser must have lots of air across it, that is what keeps the high side down to something reasonable, and the more reasonable, the better the cooling, as you have demonstrated.
Good luck with the truck, happy to help out.

I'm in Arizona, and I've had to replace fan clutches on quite a few of my vehicles.