HVAC Cooling Performance Degraded

[cfcubed]

2018 LR M3 w/only 21k miles -
While I don’t notice the behavior Sziehr described, I do have the problem others did: when car is warm/hot, climate set to AUTO, the car now takes forever to bring down temp to setpoint. The symptom is the fan speed doesn’t raise above 3 when first getting in. It used to (correctly) blast the fan/AC to quickly bring down cabin temp.

We’ve resorted to knocking down the temp to 65 for first 10 mins or so then going back to setpoint (eg 73)….. Or boosting fan speed manually.

IMO this is a newish software/firmware issue because:
- we’re low miles, we’ve lived in NH for > 2 yrs and AC gets less use
- others are seeing this
- it reads like what we see often from Tesla updates: while trying to fix one thing (complains of fan blasting faces during cooldown) they created another ( AUTO fan not fast enough for cooldown).

We’ve done a few “report problems” from the car so techs have data. Also when we pick Climate problem from Service app it will not allow @ home service…. And nearest is > 2 hrs away. And for some reason the Tesla app isn’t letting me Confirm appt. So whole situation kinda sucks as it appears to be firmware issue but service wants to throw parts at the problem & only @ service centers.

 

[tone228]

Knock on wood but the problem seems to have went away. I waited till the last minute and canceled my service appointment. I wonder if Tesla released a patch since I put in a service request, not sure if that’s even possible since I’ve never connected to wifi.

 

[Ken43]

Unfortunately, after 4 tries at the service center (JUN-JUL 2022) , my A/C problem (intermittent reduced cool air flow) still not fixed.

Visit 1: Replaced LH and RH Bleed actuator, RH Vent Actuator, RH body control module, Low Voltage controller right, Air vent assembly passenger
Visit 2: Replaced HVAC Sensor (1462944-00-A), Chiller and EVX Assembly
Visit 3: Updated Firmware (and I suspect some other tries, not listed in customer copy invoice)
Visit 4: Replaced the Relative Humidity and Temperature Sensor (1462944-00-A) again (based on a fault thrown)

Still having the same intermittent problem . Really don't know what to do at this point. Although the service advisor and myself have been very polite to each other and the service advisor seems to genuinely want to solve the issue, I don't think the local tech knows how. The tech seems to over rely on the diagnostic software to tell him how to fix the vehicle.

I'm contemplating taking the car to a large regional service center in hopes there might be a senior tech able to fix difficult problems.

 

[Big Earl]

I think the issue here is Tesla changing some of the system parameters that result in reduced performance when cabin temp is close to outside air temp. I've also noticed that if it's in the low 70 outside, I have to set the automatic temperature lower in order to be comfortable.

Otherwise, the system performs perfectly. If you're trying to diagnose this by changing parts, you're chasing your tail.

My best guess (having an HVAC background) is this is an attempt to make non-heat pump systems more efficient on mild days. Normally you'd have to run quite a bit of cooling to dehumidify, then reheat the air with PTC heat so the cabin doesn't get too cold. This obviously uses a lot of energy. I think they're trying to reduce that energy consumption by changing parameters, but the end result is unsatisfactory, requiring the user to lower the temperature in order to be comfortable.

 

[ElectricNerd]

I'm curious if our '21 M3SR+ is affected. We've noticed the AC doesn't seem as cool as it was before the latest software update (2022.16.x) and even before that my wife would constantly fiddle with the vent direction controls because as she put it she could not get the air to blow straight at her. It's either at her knees or at her head no matter what she tries.

 

[Big Earl]

I'm curious if our '21 M3SR+ is affected. We've noticed the AC doesn't seem as cool as it was before the latest software update (2022.16.x) and even before that my wife would constantly fiddle with the vent direction controls because as she put it she could not get the air to blow straight at her. It's either at her knees or at her head no matter what she tries.

Have her pinch the airflow together (how you'd pinch-to-zoom-in on a phone or tablet). This will combine the airflow into one single stream, which she can more easily direct at her face. To restore it to two streams, pinch-out.

 

[Ken43]

Everyone's AC problem is a little different. I'm glad to hear the variations as it may give someone a clue to get theirs fixed. I want to stress though that my situation , the climate control is not just a little uncomfortable. If left alone the cabin temp will climb into the upper 90s with a setpoint of 68 degrees with outside temperature in the upper 90s. My wife and I took our vehicle to the service center in this condition, both of of dripping in sweat , just so Tesla Service team would experience the 98 degree humid cabin and believe us and not blame it on midlife hormones, etc Tesla Service believed us.

I can do a voodoo dance, switch to manual mode, turn off A/C for 30 seconds and then air speed from the vents will recover (without changing the fan speed on the screen), then turn the a/c button back on again and the cooling and cool cabin resumes in a few minutes. This has to be done about every 15 minutes else the 98 degree sweatbox condition returns.

 

[jkeyser14]

My A/C is finally working properly after my 4th trip back to the service center over the past 4 months. The issue was remotely diagnosed correctly before my first visit, but Tesla was disorganized, screwed up on getting parts, and did sloppy work that left me without a car for a week and then had to be taken back to have the work redone.

 

[Ken43]

OK, I have a successful repair to report after visit 5 . The problem was the Sensor - Temperature - Evaporator (remove and replace).

Here is the narrative from Tesla:
" Inspected refrigerant pressures while operating A/C at 66 degrees with automatic climate enabled. After 20 minutes, suction pressure would reach 10psi and suction line would begin to freeze. Recovered refrigerant to check charge level. Recovered 630g of refrigerant. Low charge is not an issue. Before recharging vehicle, inspected TXV, EXV, and desiccant. All in good condition and no blockages were present. Inspected evaporator refrigerant lines for any blockages. None present and internal evaporated had no restrictions. Ran vehicle again under the same conditions. Suction side still drops to 10-15psi, suction line freezes, and compressor is inhibited to do low suction pressure. Observed evaporator temperature data. Evaporator temperature sensor reported 22-25C. Inaccurate reading as a temperature probe was inserted into the cabin vent duct on the driver's side and temperature was 14.4C. Replaced evaporator thermistor. Performed test drive under customer narrative conditions to verify repair. Automatic climate control is operating as designed.

Correction: Sensor - Temperature - Evaporator (Remove & Replace)"

 

[BigNick]

OK, I have a successful repair to report after visit 5 . The problem was the Sensor - Temperature - Evaporator (remove and replace).

Here is the narrative from Tesla:
" Inspected refrigerant pressures while operating A/C at 66 degrees with automatic climate enabled. After 20 minutes, suction pressure would reach 10psi and suction line would begin to freeze. Recovered refrigerant to check charge level. Recovered 630g of refrigerant. Low charge is not an issue. Before recharging vehicle, inspected TXV, EXV, and desiccant. All in good condition and no blockages were present. Inspected evaporator refrigerant lines for any blockages. None present and internal evaporated had no restrictions. Ran vehicle again under the same conditions. Suction side still drops to 10-15psi, suction line freezes, and compressor is inhibited to do low suction pressure. Observed evaporator temperature data. Evaporator temperature sensor reported 22-25C. Inaccurate reading as a temperature probe was inserted into the cabin vent duct on the driver's side and temperature was 14.4C. Replaced evaporator thermistor. Performed test drive under customer narrative conditions to verify repair. Automatic climate control is operating as designed.

Correction: Sensor - Temperature - Evaporator (Remove & Replace)"

This sounds like it would have required a highly experienced HVAC tech to diagnose and repair, not a tech that just replaces parts because the computer threw a code for a defective component.

 

[Sophea Sok]

OK, I have a successful repair to report after visit 5 . The problem was the Sensor - Temperature - Evaporator (remove and replace).

Here is the narrative from Tesla:
" Inspected refrigerant pressures while operating A/C at 66 degrees with automatic climate enabled. After 20 minutes, suction pressure would reach 10psi and suction line would begin to freeze. Recovered refrigerant to check charge level. Recovered 630g of refrigerant. Low charge is not an issue. Before recharging vehicle, inspected TXV, EXV, and desiccant. All in good condition and no blockages were present. Inspected evaporator refrigerant lines for any blockages. None present and internal evaporated had no restrictions. Ran vehicle again under the same conditions. Suction side still drops to 10-15psi, suction line freezes, and compressor is inhibited to do low suction pressure. Observed evaporator temperature data. Evaporator temperature sensor reported 22-25C. Inaccurate reading as a temperature probe was inserted into the cabin vent duct on the driver's side and temperature was 14.4C. Replaced evaporator thermistor. Performed test drive under customer narrative conditions to verify repair. Automatic climate control is operating as designed.

Correction: Sensor - Temperature - Evaporator (Remove & Replace)"

Thank you for this. I had the same problem as soon as i saw your post, I changed the sensor n everything is back to normal.

 

[Leafable]

OK, I have a successful repair to report after visit 5 . The problem was the Sensor - Temperature - Evaporator (remove and replace).

Here is the narrative from Tesla:
" Inspected refrigerant pressures while operating A/C at 66 degrees with automatic climate enabled. After 20 minutes, suction pressure would reach 10psi and suction line would begin to freeze. Recovered refrigerant to check charge level. Recovered 630g of refrigerant. Low charge is not an issue. Before recharging vehicle, inspected TXV, EXV, and desiccant. All in good condition and no blockages were present. Inspected evaporator refrigerant lines for any blockages. None present and internal evaporated had no restrictions. Ran vehicle again under the same conditions. Suction side still drops to 10-15psi, suction line freezes, and compressor is inhibited to do low suction pressure. Observed evaporator temperature data. Evaporator temperature sensor reported 22-25C. Inaccurate reading as a temperature probe was inserted into the cabin vent duct on the driver's side and temperature was 14.4C. Replaced evaporator thermistor. Performed test drive under customer narrative conditions to verify repair. Automatic climate control is operating as designed.

Correction: Sensor - Temperature - Evaporator (Remove & Replace)"

Wow I have exactly the same issue as yours. They change the compressor low and high pressure sensors and recharge the gas still cant solve the issue. Now you lead us to the actual tiny cheap temperature sensor. Thank you!