AC blows warm when idle on really hot days. What should I be looking at?

[Reacher19]

Hi Ranger family,
I have a 2019 ranger XLT.
I'm in construction and my truck is on most of the days here in Florida. I'll get out of my truck and leave it running for a while while I'm checking on a house. Recently, on really hot days I'm noticing when I return to the truck the air is blowing warm. When I start driving the truck it gets cold again. What could be causing this? I'd like to try to fix this but I'm not sure where to begin to look.
Side note: My truck did have the issue where the wiring harness on the fan clutch got chewed up. My fan clutch was stuck on and I had replaced it before I realized this issue. Some of the wires were frayed. I splice them back together and my fan clutch ran as normal. Recently, my fan clutch was stuck on again and I squeezed the wiring harness and it went back to normal. But the AC issue continues to happen. I'm not even sure if this is even related but wanted to mention it anyway.
Has anybody ever experienced this with their ranger? And how did you fix it?
Thanks in advance.

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[RangerBill]

If your engine cooling fan is not working properly, it would affect your AC performance, especially at idle, where the only air moving through the condenser is by the engine fan. What do you mean by " My fan clutch was stuck on"?

 

[Reacher19]

It was on all the time. Truck sounded like a garage truck 100% of the time. I figured it was just a burnt fan clutch joy had it replaced and then discovered the wiring harness was chewed up and the wires in it were afraid. When I replaced the wires it seemed to run normal. But now with this AC issue I'm not sure what to do.

 

[RangerBill]

It was on all the time. Truck sounded like a garage truck 100% of the time. I figured it was just a burnt fan clutch joy had it replaced and then discovered the wiring harness was chewed up and the wires in it were afraid. When I replaced the wires it seemed to run normal. But now with this AC issue I'm not sure what to do.

I would repair the wiring to the fan clutch. The fan will turn faster with the AC on and the truck idling. Your issue is likely the intermittent wiring causing your fan to turn too slowly. The fan should always be turning, but the speed is controlled by the PCM computer.

 

[RangerBill]

The reason your AC gets colder when driving is because the truck's movement is pushing air through the AC condenser and the fan doesn't need to turn as fast.

 

[Jason B]

That and the compressor also runs faster.
IMO, too much fan is better than too little fan, even with the 'garbage truck sound'.

 

[Reacher19]

Does anyone know which wire in the harness on the fan clutch harness has to do do with the AC?
I'm going to open it up but I'd like to know what I'm looking for

 

[RangerBill]

Does anyone know which wire in the harness on the fan clutch harness has to do do with the AC?
I'm going to open it up but I'd like to know what I'm looking for

The fan clutch doesn't have a direct connection to the AC. The PCM (powertrain control module) controls the fan speed, which is variable, based on various parameters. Engine coolant temperature, vehicle speed, AC use, etc. There won't be a specific wire in the fan clutch wiring harness for this purpose. The fact that you move the harness and the speed of the fan changes, indicates a bad connection that needs to be repaired.

 

[airline tech]

Repair the bad connection FIRST and then if the AC Issues still remain the following will be the next steps.

For Ref:

Pin 1 = 12 Volt Power

Pin 2 = PWM - Pulse Width Modulated, Control of the Fan Clutch - The control side is factoring in Engine Temp, AC Running, Engine RPM Data and Fan Speed, to control the viscous fluid movement in and out of the reservoir - To Control Fan Speed
With using the 5-Volt Ref as feedback

Part of the VREF circuit:
Pin 3 = VREF Input from Crank (5-Volt Reference)
Pin 4 = VREF Signal Return to Camshaft,
Its monitoring Engine RPM data
Pin 5 = Actual Fan Speed (FSS-Fan Speed Sense) as picked up by the Hall Effect Sensor
This is the Nubs on the backside of the fan clutch (rotating) the module (sensor) reads this as fan speed - and provides feedback to the PCM, while comparing Crank & Cam RPM data it knows the difference in speeds.

Pin 3 - PCM ---Crank----Fan - VREF (5-Volts) Input
Pin 4 - Fan ---Cam -----PCM -VREF (Signal Return)
Pin 5 - (= the speed signal of all) Rotational Speed - To the PCM

There is not a specific wire for (Is AC Compressor - On) for the Fan Clutch
It is a PCM controlled function.

Once wiring bad connection (splice) is repaired and the AC issue remains then these are the next steps.
But I would scan for codes and clear them (if any are present) afterwards.

At Idle if freon level is low, there is not enough freon in the system to provide cooling when the compressor is spinning at a low rotational speed and quite possibly disengaging the clutch.
When you drive come above idle the Freon can move faster thus provide cooling and if the clutch is actually disengaging - it will now engage. (AC Pressure) is increased

So, you can possibly test - when you are at idle and you press the AC Button, are you hearing the AC Compressor Clutch - Click (Engage)
If NO
Try it again by raising the RPM's

Same goes for the clogged condenser - at idle you are relying on the fan to pull air through the condenser if clogged with debris this can cause AC Performance issues, but you would most likely see an elevated engine temp as well.
When you drive, you have forced air flowing across the condenser and this will overcome a clogged condenser (debits).

I am thinking Low Freon level is the cause.
and this will affect the actual temperature output while driving

 

[Reacher19]

Thanks for that detailed answer. It's very much appreciated. I will start with checking the wires in the harness for a bad connection. Hopefully that's all it is. Otherwise, I'll go through the steps you described.
Thanks again ?

 

[Cabose-1]

Be sure the radiator, condensor, cooling thing for the turbo are all free of dirt and debris. Dust can collect on the cooling fins causing it to not cool properly, or air to pass freely through them.
Having the samebissue here in south texas. But its hot during the day and slow moving traffic. Once i drive a bit with air moving through the front it cools off again.

 

[Jason B]

People have also reported some debris between the AC condenser and radiator, so check that too.

 

[dstig1]

+1 fix wiring for real FIRST and blow out the condenser from behind, carefully so as to not bend over fins. With a truck that is a few years old, AC used heavily and in dusty environments, it could be dirty and reduced efficiency.

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