Ford Ranger Compressor Cutting Out

[Autosaver]

Ford Ranger
Year: 2018
Engine: P5AT
Model: PX/PXII

AC is cold when engine is idling & for a short while when driving but when car is driven for 10-15 minutes the AC goes warm. The AC has to be turned off for a bit & then it's cold again but then the issue repeats itself when driven again for another few minutes.

Connected gauges & AC charge is good, 55psi (low side), 300psi (high side) - believe me 300psi for the PX model Ford Rangers is standard (plus I'm in a tropical climate).
Scanned vehicle for error codes - none found
Checked radiator fan & viscous coupling - okay
Checked condenser for debris - okay

What happened next was I monitored the gauges while someone sat in the car and held the engine at 1500-2000 rpm. What happens is that the with the engine revved, the high side pressure climbs to over 400psi & then the compressor cuts out. The car is then allowed to idle and the pressure then drops back close to 300psi, the compressor turns back on & the whole cycle repeats itself (engine rpm > 1000).

I had a look and the high pressure gauge port is between the condenser exit & the TX valve. Based on this I'm thinking that the TX valve is not opening fast enough so then there is a pressure build up behind it which is then causing the compressor to cut out.

I'm looking at changing the TX valve & also the condenser dryer filter (precaution).

Just looking for a second opinion before I go ahead & spend the money on the parts.

Thanks in advance.

[tbirdtbird]

Your HPCO is cutting off your comp. Over 400 psi hi side as you stated is too high. Condenser not doing its job. See below
May also be overcharged since your 55 and 300 are too high regardless of your climate.
Has anyone worked on the system lately? What was done. Obviously the car was not always like this.
"Checked radiator fan & viscous coupling - okay"
How do you really know this? The fluid coupling tends to deteriorate with time and does not allow enough air thru condenser. Need massive air flow especially in your climate. We advise changing fan clutches every 3 yrs

[JohnHere]

I agree with the previous comments. The extreme pressures you're seeing point to an overcharge primarily. Secondarily, a lack of airflow across the condenser and/or air and moisture in the system could also contribute to the sky-high pressure readings.

Remember that pressures don't tell you how much refrigerant is in the system. Begin by recovering the existing refrigerant, re-charging to specifications by weight, and then performance-test the system.

[Autosaver]

Well I haven't had too many Ford Ranger through the shop but all of the ones I've placed gauges on, even those with a good operating AC, have had a high side pressure 290-300 psi.

To my knowledge, no one has worked on the AC prior to me checking it. The issue happened a few weeks ago & the owner turned up to the shop with some r134a cans asking me to refill it. I checked & then advised him that there was enough refrigerant in the system.

Viscous coupling - I left the car to cool & then forcefully rotated the fan. No more than 1 rotation when cold then pretty much stiff when rotated when engine was warmed up. Car has only 50,000km (31,000 miles) so it's still fairly new. I don't know if this is the best way to test a viscous coupling fan so if you can advise on a better way, I'm all ears.

My only means of testing the condenser was a touch test. During normal AC operation I placed my hand on the inlet pipe & fins (left hand side) & then compared the temperature to the outlet pipe & fins (right hand side). The outlet side was much cooler than the inlet so I just concluded that the condenser & fan were doing their job well enough.

Does it make sense to anyone here that a slow opening/responding TX valve would create a temporary restriction, causing pressure to build up & the compressor to cut out via high pressure switch? With pressure readings the build up is always before the restriction & for this Ranger the high side gauge port is between the condenser outlet & TX valve.

I've taken into account the previous comments & will relieve some of the pressure in the system.

[tbirdtbird]

Re-read what JohnHere and I just wrote.
The problem is not the TXV.
I am gonna guess that someone added more 134 to make up for the deficiency of the condenser not getting enough airflow. Just replace the fan clutch already. This comes up all the time. Why else would the owner show up with more cans of 134??! Chuckle.
As to your other experience with Rangers, we cannot address that without details, only this one car. But be assured that 55 lo and 300 high are NOT normal readings. With those pressures you are gonna blow a hose and someone will be blinded by the nearly explosive flash of the refrigerant when that happens.

Use your infrared temp gun to shoot the temps of the pipe into and out of the condenser and report back, along with your state, and the ambient.
Testing s/b done at 1500-1800 RPM, doors open, max fan, max cool.
Once you have gotten the temps from above, use a garden hose and wet down the condenser and repeat your readings and pressures and report back. The pressures will drop like a rock, proving inadequate condenser function.

The only way to properly and accurately charge a 134 system today is by doing what JohnHere asked of you....recover, and weigh in correct amount. Any other way is just a guess.
The days of doing it your way went out the window with the termination of R12

[JohnHere]

Both the high-side and low-side pressures are too high as previously mentioned. With a low side of ~55 PSI, you are looking at an evaporator temperature of around 60°F, far too warm to provide any measurable cooling. A high side of ~300 PSI, even at 100°F, suggests a condensing issue. You've checked into that, though, and found no problems with airflow. That leaves an overcharge, which would be my best guess, or air and moisture in the system.

"Adjusting" the refrigerant amount downward still doesn't tell us how much is actually in the system. The only way to know that for sure is to recover, evacuate, and re-charge to specifications, which should appear on an under-hood decal.

[tbirdtbird]

I take issue with his determination of condenser fan function, but getting the proper charge in there with a fresh evacuation (could be air and moisture contamination also as you mentioned) is the correct starting point for further eval.

[JohnHere]

I take issue with his determination of condenser fan function

Right...it would also be helpful to get actual condenser inlet and outlet pipe temperatures instead of just going by feel to determine how the condenser is performing.

[Autosaver]

So if I used an infrared thermometer I'd be looking for the temperature difference between the condenser inlet & outlet?

What's an acceptable value? Does this value vary depending on the vehicle?

Thanks

[Autosaver]

QUOTE

"wet down the condenser and repeat your readings and pressures and report back. The pressures will drop like a rock, proving inadequate condenser function"

I actually thought to do this on the day but regrettably skipped it...

Based on your statement, 'theoretically' if I did run water over the condenser & the pressure didn't drop like a rock & stayed relatively close to the original then would you say that the condenser was doing working well enough?

Thanks