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Ford Ranger
Year: 2018
Engine: P5AT
Model: PX/PXII
AC is cold at idle & a short while when driven 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.
AC charge is good, 55psi (low side), 300psi (high side) - believe me 300psi for the PX model Ford Rangers is standard.
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 pressure then drops back close to 300psi, the compressor turns back on & the whole cycle repeats itself (engine rpm > 1000).
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.
I don't think that the evaporator is freezing up. I had a look at the evaporator temp sensor reading on the scan data and it is not dropping low enough to cause freezing. The TX valve is also not freezing up.
Cabin air filter is also not an issue as the air flow through the vents is very strong.
I also know it's not a low charge issue because the gauge readings are on point when AC is operating okay (low side 55psi, high side 300psi).
As previously mentioned, the high pressure builds up over time as the engine is revved. It gets too high which then causes the compressor to cut out. It looks like a restriction to me.
300psi on the high side is way too much.
needs to be closer to 200-250 psi when hot..
You either have a restriction or it's been over charged, this would be why the high/low switch is kicking in.
Yes I agree, there is a restriction, but where? Based on the plumbing I think it's the TX valve.
Overcharge? No, I disagree, the AC hasn't been refilled at any time according to the owner of the car. Still pretty low mileage too - 50,000km.
I've had a lot of Ford Rangers come through & 300psi on the high side for an good operating AC is standard. I've also stuck the gauges on a brand new Ranger & this too was the case. Also I live in a tropical climate where room temp. gets as high as 32C OR 89F
How long does it take to equalize ? If it takes a while then tx valve would be my assumption as well. Put a temp gun on both sides when it's running see if low side of tx valve gets warmer and compare it to high side if they get close to one another then tx valve it is.
This may help you, it's extracted from the service manual.
There is also a TSB for the clutch fan, maybe a good idea to check that it's working correctly.
Last edit: 1 year 7 months ago by Rallymechanic. Reason: attachments not displaying correctly.
Just for the sake of discussion:
There is a TSB for the fan clutch but from my experience, when it comes to AC, faulty cooling fans usually make themselves known when the engine is idling.
Because air flow is reduced when the car is at a stand still, the AC tends to go warm during this time. Once the car gets moving the air flow is sufficient enough to cool the condenser & the AC goes cold again.
The Ford Ranger I had a look at went warm after 10-15 minutes of driving. At idle the AC is cold but when revved >1500rpm & held there for a few minutes the AC goes warm.
How long does it take to equalize ? If it takes a while then tx valve would be my assumption as well. Put a temp gun on both sides when it's running see if low side of tx valve gets warmer and compare it to high side if they get close to one another then tx valve it is.
By equalize do mean: for the high side to drop back to 300psi where the compressor then kicks in again? This takes a few minutes after the engine is allowed to idle again & is gradual.
I can't really remember what the pressure reading on the low side does during this time.
I really can't remember the static pressures but I think they weren't equal.
When driving the owner said that the AC has to be turned off for a few minutes when driving, how much is a few? I'm not too sure.
That being said, when I turned the AC off after revving the engine (and compressor cutting out) it took about 4-5 minutes for the pressure to drop back to 300 psi where the AC compressor then came back on
TX valve & condenser dryer filter were replaced. System was vacuumed & refilled with the correct amount of r134a.
The high side pressure sat way lower than the initially observed 300psi - 210 to 220 psi to be exact. Low side at 45 to 50 psi.
Had someone rev & hold the engine > 1500 rpm & the high side only went as far as 250 psi. During the initial inspection the high side pressure started at 300 psi & increased to 400 psi, when revved & held > 1500 rpm, which then caused the compressor to cut out.
Because the high side slowly climbed to 250 psi I'm thinking I should've also replaced the condenser. That being said I did a general 'feel' test the first time & the outlet was cooler than the inlet. Whether I might also have a blockage in one of the tubes? I don't know, I didn't have an infrared thermometer to go across the condenser tubes.
Took the car for a 20-30 minute test drive, up hill, to keep the engine at it's warmest & rpm high. The AC stayed cold throughout the test drive. Thermometer vent readings dropped as low 1 degrees C - mind you it was a cool overcast day today (ambient temp ~ 29 degrees, ~ 25 degrees C at the higher end of the hill)
Anyways I got a hold of the old TX valve & held a heat gun to the sensing side. When heated, the valve did not move. Just wondering if this is a valid bench test for a TX valve?
sounds like you have it fixed, good job.
Does look like it was a failing TX valve or receiver dryer restriction.
I also posted this topic on another forum & they are saying that I just had an overcharged system.
Thing is that I know the car owner well & he doesn't really take his car anywhere else. When he turned up I assumed he hadn't refilled the system at all - he has no hose to connect to the r134a cans. I just assumed it was untouched...
That being said you were correct, 300 psi is way too high. I've had 2-3 Ford Rangers come in (one after a compressor replacement, vacuum & refill) and they all had high side pressures of 300 psi. Safe to say they had an underlying issue OR were just overfilled.
Another thing to add is that the new TX valve was a different design compared to the old one. Is this possibly a redesign/recall? The part is genuine Ford & based off the VIN. Refer attachment..
