2019 Fiesta SE No A/C

[Vegas]

I have a 2019 Fiesta SE and the AC is not getting cold I'm pretty familiar with late 90s and early 2000s AC systems however this one is a little different. When I turn the AC on the AC light comes on but the compressor does not engage I bypassed the AC clutch relay and the clutch engages. Looking for the low side pressure switch I cannot find it anywhere between the compressor and the firewall? Anyone have any idea where the low side switch is? The gauge reads 40 PSI on the low side so that would indicate enough pressure for the low side switch to remain closed but I cannot find the switch. Ac compressor fuse is good as well as climate control fuse behind the glove box. The high side switch is on the side of the condenser and it is a three wire switch. Anyone have any troubleshooting ideas? It's a 2019 and has less than 10,000 miles on it.

 

[Handy Andy]

The pressure transducer is a SINGLE sensor - with three terminals - one for too low, one for too high - with 3rd as the constant power to it - so it's dynamic and located near the lowest portion of the system where the oil and fluid portions of the Freon are at rest.

Since it's pressure - the balance of it, the sensors are equal in response.

When too low, or too high in pressure, it upsets the balance one output rises - the other falls.

The PCM uses this information so the system can perform in a wider variety of environments without "Freezing" or boiling the system like earlier days that use just a set level and there you go, if it ices up - thaw it out, if it doesn't produce enough bring it in and we'll fix it - by evacuation and recharge

The Sensor is located at the Radiator - Lower Right side - in the condensers "dryer" section - on the bottom.

Find the long tube next to the condenser and follow it down to the bottom of it - the tube that comes off it to the compressor, that has the sensor.

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One of the many failures I've seen, is when they "add more refrigerants" and expect it to work, it is only a quick fix but short term only with long term expensive results.

Amongst the fails are

Synthetic mixing with conventional oil base - too much oil in the system - too much FREON in the oil foaming and unable to be pressurized correctly to even cool the system (too much freon) can damage the nozzle used to make the low-side cool.

With these changes - it's not as simple as it once was.

 

[Vegas]

Ok great Thanks Andy im going to check it out today.

 

[Vegas]

Update. So with the single high/low pressure switch a typical 35-40 psi is not enough to trigger the compressor to engage the clutch. The car was in a mild environment and the ac had only been used 1 time in 5 years 10'000 miles so likely drying out the shrader valves allowing it to slowly leak out over the years. It seem to do well under a vacuum so recharged and threw in some dye to trace any leaks and now it blows ice cold even in 107 degree heat today.

 

[Handy Andy]

Nice work!