Hey guys, I'm Troy.
I just bought a 2010 MKS Ecoboost a couple weeks ago with 27k miles and I've been trying to get it into tip-top shape. Unfortunately, it's already had a few problems I've had to address (first, clogged sunroof drains resulting in flooding and subsequent sunroof motor failure, rear window regulator failure, and then the apparently notorious blend door actuators [recirc and driver blend]) .
Now that those are all taken care of, the heat is setting in and I'm realizing the A/C compressor is not staying on. Sometimes it works more or less okay, and when the compressor is on, the air is nice and cold, but other times the compressor comes on for about 1 second, and then stays off for 9 seconds, and repeats. Obviously this is basically worthless for cooling the car, so I'm trying to figure out what the deal is. The system has a good charge and runs around 45 psi at 80 degrees ambient on the low side when the compressor is engaged, so I think I'm looking at a bad sensor.
After digging around, I found some threads on a Flex forum about bad evaporator temp sensors and a TSB applying to 2009 MKS', but not 2010. I'm inclined to think this temp sensor or one of the pressure sensors is bad.
What sensors does this car have that control when the compressor is engaged? High, low, and evap temp? Are there any common issues I should be looking for? Are there any diagnostic HVAC modes I can access or test procedures available? Like I said, if I could get the compressor to stay on, it would cool the car just fine, but as it is, the <10% duty cycle is pretty worthless.
Could definitely be the AC pressure transducer/switch. You verified pressure with pro gauges? What did the high side pressure look like?
Codes can be retrieved with a code reader, or an OBD II adapter & Torque Pro software.
I ran forscan and monitored as many A/C related PIDs as I could find, and it seems to me that the data confirms the compressor clutch is working when requested. The temperature was only around 65 today, but the compressor was again only staying on for very short bursts as shown. I still need to get a hold of some pro gauges and compare their readings to what the data is showing, but I otherwise have no idea what I'm looking at pressure wise. Can anyone comment on what this is showing? I'm assuming this is high side pressure, and assuming that it's cutting off the way it should when it exceeds a certain pressure and I should therefore be looking at a possible faulty pressure sensor?
Also, the temperature I was monitoring was "Ambient Air Temperature." Is that the Evaporator temperature sensor or is that the interior temp sensor?
Ambient air temperature is from the sensor behind the grille/bumper cover.
Either a bad sensor as you suggested or the system is overcharged. You could try purging a bit of refrigerant to see if the issue goes away.
Quote from: SHOdded on June 07, 2019, 01:09:23 AM
Ambient air temperature is from the sensor behind the grille/bumper cover.
I considered that too, the only thing is that the my Sync screen was reading 65 degrees at the time, while the AAT in forscan comes out to 57 degrees.
Thanks for the help guys...The system just turned out to be overcharged after hooking up some proper gauges.