Need A/C and cooling fan logics

[NahumCC]

Hello,

I’ve got a 2014 Explorer Limited and I’m looking to get more information about the logics that control engaging/disengaging the A/C compressor and the radiator cooling fans. The other day over a 12 hour drive I noticed the A/C wasn’t cold.

I just got my OBD LINK the other day and confirmed with FORScan Lite I had lost my A/C charge. This morning I had attempted to charge it up with UV dye to find where the system was leaking from and noticed the compressor wouldn’t come on to support pulling in a decent charge (low side A/C pressure readings maxed out at 31 psi).

With this information, and my experience and knowledge of A/C and radiator fan logics from maintaining my 2 Saabs (I know they won’t be the same values or specific logics but expect them to be fairly similar enough to help figure it out what to look for), I activated the PIDS in the HVAC and PCM modules to identify if anything jumped out besides the low R134A pressure, checked for any DTC’s that were pending or wouldn’t set a CEL, and ran the HVAC/PCM self tests.

There were no DTC’s, the self tests passed, and the only PID that stood out was the PCM PID for Air Conditioning Compressor Command State which stayed in Off no mater what. All the other condition states were in the “on” or “no fault” states. See the below screen captures from my tests after driving back home. There was about a 4 psi drop on the low side pressure circuit over 4 hours that occurred from when I charged up the A/C to taking these screen shots.

Please ignore the engine cooling temp deviations. They all tracked within 1 degree of each other. The difference in the below screenshots occurred over the time of taking the screen shots and editing them. Temps were never more than a degree apart. Both cooling fans came on at 212F on the low fan speed setting and LFC state was showing on when running.

I don’t have a IDS/FDRS license so I can’t get the workshop technical data that has the answers I’m looking for. Appreciate any help on what to look at for T/S and testing to get the compressor clutch engaged.

The compressor is only about 2 years old and was replaced at the local Ford dealership. Once I’ve got whatever issue is preventing the compressor from working and fix the source of the leak I have everything on hand to draw a deep vacuum and meter in the correct mass of R134a into the A/C circuit.

Thanks in advance for any and all help.

 

[ProjectSHO89]

Have you connected an actual manifold gauge to see if the ACP PID correlates? If so, what do they read and at what ambient temperature? If the ACP sensor output is too low, clutch operation is inhibited. It won't be enabled until the pressure is high enough. See below.

This morning I had attempted to charge it up with UV dye to find where the system was leaking from and noticed the compressor wouldn’t come on to support pulling in a decent charge (low side A/C pressure readings maxed out at 31 psi)

Under what specific conditions were those? With a refrigerant can or tank connected and the valves all open, you should read the pressure from the external source. If you warm the refrigerant container up to around 100-120F (hot water works), you'll get plenty of pressure.

 

[NahumCC]

@ProjectSHO89 thanks for jumping in. Ambient temp in the morning when I added was ~48 degrees. I added from an older R134A refill can that I had on hand knowing it was gonna leak down. It had an external digital gauge but unfortunately the battery was dead for it and I didn’t have a spare CR size battery.

I do recognize a minimum low side pressure is a logic setting common across all manufacturers for an A/C compressor to be engaged by the PCM if the demand signal from the ACC is present. Do you know what that is for the 5th gen Explorer? My old can may not have had enough charge to meet that value once it equalized with the low side of the system. This was why I am asking for all the logic criteria Ford uses and the values of those set points.

My Elitech EMG-40V showed up last night but the R134A adapters won’t get here until later today. Murphy played a cruel trick with the R1234YF adapter set arriving first. I’ll post up a snap shot from the manifold display and from the FORScan PID display for comparison as well as the local temp at the time I grab those measurements to confirm the ACP sensor is accurate.

Ultimately I’m not concerned with temp at the time of recharge once I’ve fixed the leak as I’ll be filling to the specified R134A mass of 1.162 kg from the radiator support A/C sticker with a smart scale and metering solenoid that closes off once the set value has been metered by the solenoid and matches with the scales reduction of mass from the R134A tank.

 

[NahumCC]

Well now that Amazon got me my R134A adapter set….looks like I also have an A/C Pressure transducer needing replaced. As soon as I hooked up initially Elitech showed zero while FORScan had 17psi. Bumped it with the near end of the Freon van and Elitech came up confirming it. Now I just gotta finish finding the leak.

FORScan

Elitech Digital manifold

 

[NahumCC]

So I ran a quick test today to verify the old sensor is suspect after picking up a new sensor. Ignore the AC_Clutch on. That’s from the HVAC PID status of the HVAC request.

Old sensor before being unplugged.

Unplugged it went to zero as it should showing I don’t have a PCM issue.

Plugged in replacement exposed to atmosphere.

So I learned, even though it’s not explained in the details of either of the 2 PID PCM.ACP_PRESS options one is scaled to read atmospheric with no adjustment and the other has a PCM adjustment reducing it by .5 BAR.

Certainly a little confusing to not have that explained at all in FORScan lite. Gonna swap out and get the vacuum drawn and recharge and hopefully find the leak quickly.

 

[NahumCC]

Swap done for the pressure sensor and nothing in the lines. Got the high and low side max vacuum values that I could pull before the vacuum pumps leak logics kicked in and stopped the draw. Knew it wouldn’t get to where I wanted. Was curious how far down I could get it.

Best the high could get down to was 640 microns.

Best low side achieved was 460 microns.

Here is the manifold reading at hook up after removing the vacuum pump.

Interestingly FORScan lite doesn’t show negative values for the PID PCM.ACP_PRESS either.

Started to charge it up from fresh cans with the goal of getting the compressor to be commanded on and to see the clutch engage. It’s 49F here and I stopped after one can because I was concerned that I still wasn’t seeing or hearing the compressor engage and the pressure on the high side coming up like this and holding wasn’t making any sense to me from the basis of PV=nRT.

This is what FORScan lite was showing.

So while letting my mind chew on what wasn’t making any sense at all I moved on to checking with the refrigerant sniffer and UV light.

Looks like I may have been leaking from the rear evaporator connection.

Where is the second expansion valve for the rear evaporator core at? Was thinking about this since there has got to be another one being so far away from the main cabin.

Anyways, so I decide to call it quits for the night and as I was cleaning up I must have hit the graph button on my manifold….not sure why I couldn’t mirror this same graph from my phones connection but oh well.

However that sudden drop from when I was going around with the sniffer should have been pretty obvious. It nagged me enough that I went back out with a better flashlight to take a look at the compressor again.

So my quick frame of reference before starting the car.

And to my surprise I got to watch it kick on (the riveted points that were my reference point are spinning)!

So the next thing I went to look at in FORScan Lite was what PID values were misleading me the whole time to the compressor not engaging.

Turns out the PID AC_CLUTCH is misleading. It always said on when it’s off and off when it was running.

You want to see ACC_CMD as on and AC_REQ as yes. If those are in those condition the A/C compressor clutch should be engaged and running.

So now I’ve got 10.8 ounces in there with leak dye, a brand new pressure sensor which was needed since the other one was off at atmosphere readings anyway, and just need to deal with the rear evaporator O-rings at the junction.

 

[NahumCC]

Charged up to 41oz. Good values at max a/c for front and rear zones. You can see the change once auto is selected and the AC is cut out for heat and then everything making its way to equilibrium with the car off.

 

[peterk9]

Looks like I may have been leaking from the rear evaporator connection.

View attachment 462939
View attachment 462940View attachment 462941

This area has been a common site for an A/C leak.

A/C Rear Line Leak

Just heard back from my stealership that both hoses that link back to the rear evaporator on my 2011 Limited Explorer (with about 75000km) have cracks in them that let all the coolant gas out. What gives??? It seems that they have rusted out near the evaporator. OK, granted I live in Canada...

www.explorerforum.com

Peter

 

[NahumCC]

But back to the original question of this thread. Does anyone have the logics. This was what I was hoping to find here.

And something like this for radiator fans logics based on A/C pressure if Ford does that.