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Possible frozen AC evaporator

superdry

Member
Aug 19, 2020
21
12
Texas
I had a recent experience in my 2020 Model X (Raven) that I wanted to share. I was driving an extended period on a hot day (100+ degrees), and over the course of a couple of hours, the A/C gradually got less and less effective. I could hear the compressor screaming (as it tends to do normally under hot conditions), and the air was coming out of the vents cold. The problem was the volume of air was slowly diminishing, to the point where it couldn't keep the cabin cool. I had the temperature setting set to LOW. I tried Auto fan speed vs 11, and various output vent settings, but to no avail. I could hear that the blower was running at full speed - it was just that the airflow out the vents was diminished, as if there was blockage somewhere. Tesla customer service's only suggestion was a reboot, and if that didn't fix it, bring it into the service center. A reboot didn't fix it. But, just letting it sit overnight returned it to normal operation. Thinking back on it, I'm guessing that the problem might have been a frozen up evaporator. In addition to being very hot, humidity was higher than normal due to recent rains. I'm guessing that the combination of humidity, Low temp setting, and extended driving resulted in the evaporator icing over, and that letting the car sit for a few hours caused the problem to just melt away - literally.

I tried searching, but couldn't find much mention of this as a common problem. Also, if it were at all common, I would have thought that Tesla phone support would know about it and suggest letting the car sit for awhile rather than recommend bringing it into the service center. Anyone else have a similar issue?
 

mjptech

Being cyberbullied by TMC users PhilDavid + DCEV
Mar 30, 2019
527
243
Ventura
The vehicle prioritizes battery cooling rather than passenger cooling. A number of us have experienced it (in one of the subforums, there's more posts about this). I had this happen when my wife was pregnant a couple of years ago - hot day out and the AC went out... Went over to a nearby service center, and was told to just let it sit for a few hours...

After those few hours, everything was back to normal.
 
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mxnym

Active Member
Mar 9, 2018
1,080
443
Bloomington, IN
The vehicle prioritizes battery cooling rather than passenger cooling. A number of us have experienced it (in one of the subforums, there's more posts about this). I had this happen when my wife was pregnant a couple of years ago - hot day out and the AC went out... Went over to a nearby service center, and was told to just let it sit for a few hours...

After those few hours, everything was back to normal.
Yes, several people have experienced battery cooling taking over, and I believe they complain that the air is blowing hot because all of the cooling capacity is being directed at the battery. That is not what OP asked about. OP is experiencing a lack of air flow. AFAIK, the blowers in the cabin have nothing to do with the battery cooling and OP issue is a different one. Frozen evaporator sounds feasible to me, but I'm no expert.
 

mxnym

Active Member
Mar 9, 2018
1,080
443
Bloomington, IN
Do you have a 5 seater?
I got a 7 seater for the sole purpose of the larger compressor.
I've heard the incorrect "second compressor" comment many times. I haven't heard the "larger compressor" suggestion before. Do you know if there are actually two different compressor part numbers? Otherwise, it is possible that the "larger compressor" is just something an OA pulled out of you-know-where... In either case, compressor size wouldn't have any bearing on airflow through the front vents.
 

scottf200

Active Member
Feb 3, 2013
4,216
4,049
Chicagoland ModelX S603
The single HVAC system (5 seat X) has one compressor, two evaporators (one for battery cooling and one in the dash) and one PTC heating element (6 kW in the dash).

The dual HVAC system (6 and 7 seat X) has one compressor, three evaporators (one for battery cooling, one in the dash plus a smaller one in the rear) and two PTC heating elements (6 kW in the dash and 2.5 kW in the rear).

The extra refrigerant required for the dual unit is due to the extra evaporator and the refrigeration lines that run from the front of the vehicle to the rear of the vehicle. The system does not have two compressors.

Do you have a 5 seater?
I got a 7 seater for the sole purpose of the larger compressor.
It appears to be an extra evaporator coil is to cool the refrigerant so that it can absorb the heat but I've never seen anything (or two part numbers in the catalog mentioned) about a larger compressor.

A related thread that points to other threads here: Reat seats AC - Model X
 
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mswlogo

Well-Known Member
Aug 27, 2018
6,160
5,318
MA, NH
It appears to be an extra evaporator coil is to cool the refrigerant so that it can absorb the heat but I've never seen anything (or two part numbers in the catalog mentioned) about a larger compressor.

A related thread that points to other threads here: Reat seats AC - Model X

There are two separate part numbers for the compressor. One "normal" and one "NO RHVAC" (no rear HVAC).

1MX, COMPRESSOR, A/C ELECTRIC1042442-00-MOver-the-Counter(No VIN)11
1A/C COMPRESSOR, ELECTRIC, NO RHVAC1063369-00-JOver-the-Counter(No VIN)11
 
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mxnym

Active Member
Mar 9, 2018
1,080
443
Bloomington, IN
There are two separate part numbers for the compressor. One "normal" and one "NO RHVAC" (no rear HVAC).

1MX, COMPRESSOR, A/C ELECTRIC1042442-00-MOver-the-Counter(No VIN)11
1A/C COMPRESSOR, ELECTRIC, NO RHVAC1063369-00-JOver-the-Counter(No VIN)11
If "(not) NO RHVAC" means "bigger," as opposed to "extra coolant line connections," then I'd hate to see how pathetic cooling must be in a 5-seater.
 

mswlogo

Well-Known Member
Aug 27, 2018
6,160
5,318
MA, NH
If "(not) NO RHVAC" means "bigger," as opposed to "extra coolant line connections," then I'd hate to see how pathetic cooling must be in a 5-seater.

I'm not sure what your saying. But "NO RHVAC" would likely be a smaller unit and have less connections.
Yes, it's possible it's a variation of the same compressor with more outlets for the 6/7 seater.

There have been numerous reports that the 5 seater cooling system is endemic, it's the only reason I opted for 7 seater.
In 2 years years no one has ever sat in the rear seats and they are always folded down.

I'll bet the OP has a 5 seater.

I've had zero issues with mine and never heard the compressor screaming.

You stated there was not two part numbers but there is.

The system will prioritize cooling battery over cabin. Which also explains the OP behavior.

One way to check evaporator frozen would be to run OBDII setup.
 

mxnym

Active Member
Mar 9, 2018
1,080
443
Bloomington, IN
I'm not sure what your saying. But "NO RHVAC" would likely be a smaller unit and have less connections.
Yes, it's possible it's a variation of the same compressor with more outlets for the 6/7 seater.
Yeah, I couldn't come up with a better way to word it, but we're saying the same thing, we don't know for sure that the one that supports the extra condenser is "bigger" (presumably meaning higher BTU).
There have been numerous reports that the 5 seater cooling system is endemic, it's the only reason I opted for 7 seater.
In 2 years years no one has ever sat in the rear seats and they are always folded down.
I have a 7 seater, the A/C is practically worthless if it's over 90 degrees Fahrenheit and sunny outside. This is when only I am in the vehicle. I also have issues with the rear A/C specifically that lead to my kids baking in mild weather and the service center cannot reproduce it.
I'll bet the OP has a 5 seater.
OP may have the 5 seater, but air-flow through the front vents has nothing to do with the compressor, and that was OP's complaint, lack of air flow.
You stated there was not two part numbers but there is.
No, I didn't:
Do you know if there are actually two different compressor part numbers?
I've had zero issues with mine and never heard the compressor screaming.
What is your weather like? Mine sounds like a jet when preconditioning all summer long. I guess something also may have changed for the Ravens, mine is a 2017.
The system will prioritize cooling battery over cabin. Which also explains the OP behavior.
You may be correct, as I may be reading too much into this:
The problem was the volume of air was slowly diminishing
One way to check evaporator frozen would be to run OBDII setup.
Great advice, but OP would have to experience the issue again and have access to such a setup. Further, I've read that the OBDII port doesn't provide all information required by the standard and was only included due to regulatory requirements. I don't know how true that is.
 

mswlogo

Well-Known Member
Aug 27, 2018
6,160
5,318
MA, NH
Yeah, I couldn't come up with a better way to word it, but we're saying the same thing, we don't know for sure that the one that supports the extra condenser is "bigger" (presumably meaning higher BTU).

I have a 7 seater, the A/C is practically worthless if it's over 90 degrees Fahrenheit and sunny outside. This is when only I am in the vehicle. I also have issues with the rear A/C specifically that lead to my kids baking in mild weather and the service center cannot reproduce it.

OP may have the 5 seater, but air-flow through the front vents has nothing to do with the compressor, and that was OP's complaint, lack of air flow.

No, I didn't:


What is your weather like? Mine sounds like a jet when preconditioning all summer long. I guess something also may have changed for the Ravens, mine is a 2017.

You may be correct, as I may be reading too much into this:


Great advice, but OP would have to experience the issue again and have access to such a setup. Further, I've read that the OBDII port doesn't provide all information required by the standard and was only included due to regulatory requirements. I don't know how true that is.
It will approach near 100F (occasionally over) a few times a summer and very humid.
I use Dog mode all the time and watch it VERY closely. I physically go and check it and set a timer to check App every 5 minutes.
I usually won't leave it in direct sun though if the dogs are in it. Even though it would run fine, I wouldn't trust it.

Mine is a Raven 7 seater. I have heard of problems with obstructed ductwork from improper assembly.

I never precondition Winter or Summer.
 
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superdry

Member
Aug 19, 2020
21
12
Texas
OP here. I indeed have a 5-seater, and until reading the responses in this thread, had no idea there were HVAC system differences based on seat configuration. That's good information to have, but I don't think that's been an issue for me in general. I've driven it all summer in very hot weather (like 120F) and in general not had cooling problems that I wouldn't expect in any car being operated in those conditions. I have 30,000 miles on the car, and maybe 10 of those miles had more than 2 people in the cabin. Also, having lived with the 5-seat configuration, if I had it to do over, I don't think I'd get a 7-seater: although the extra HVAC capacity sounds alluring, I think I value the extra cargo space more.

Also, I am aware of the "battery pack cooling takes precedence over cabin cooling" situation, and have experienced that before on an occasion or two. As others have already pointed out, the symptoms of that are different than what I'm reporting here: that situation results in normal airflow but not cold air blowing, whereas what I'm talking about in this thread is cold air blowing but not very fast, despite the blower motor sounding like it's on 11.

At this point, I'm somewhat convinced that a freeze-up of the evaporator coil was my problem. I'm surprised more people haven't had this happen, but I may have just had a rare set of circumstances that day. I'm also surprised that Tesla telephone support didn't seem to know anything about it. Their solution was a) try a reboot, and b) bring it in if that doesn't fix it. If this were at all common, I would expect them to suggest letting it sit for a few hours and see if it goes away, as I think they'd want to discourage people bringing cars in when not necessary. Maybe implicit in the situation is that I'd have the good sense to not do so if the problem only happened once and went away on its own, which is exactly what happened.

Thanks all for your input.
 
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mongo

Well-Known Member
May 3, 2017
13,448
41,942
Michigan
At this point, I'm somewhat convinced that a freeze-up of the evaporator coil was my problem. I'm surprised more people haven't had this happen, but I may have just had a rare set of circumstances that day. I'm also surprised that Tesla telephone support didn't seem to know anything about it. Their solution was a) try a reboot, and b) bring it in if that doesn't fix it. If this were at all common, I would expect them to suggest letting it sit for a few hours and see if it goes away, as I think they'd want to discourage people bringing cars in when not necessary. Maybe implicit in the situation is that I'd have the good sense to not do so if the problem only happened once and went away on its own, which is exactly what happened.
If your AC system has a low charge (but above the point where the pressure switches disable it), the evaporator can freeze up. Could also be a failed expansion or control valve.
 
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mongo

Well-Known Member
May 3, 2017
13,448
41,942
Michigan
If your AC system has a low charge (but above the point where the pressure switches disable it), the evaporator can freeze up. Could also be a failed expansion or control valve.
Might also be the evaporator temp sensor, if it has one. I think the expansion valve is electronic.
 

verygreen

Curious member
Jan 16, 2017
2,945
11,514
TN
bad temp sensor is a common problem that results in activating evaporator freeze protection. It's widely documented too. There's no user visible messages when it happens (unlike when battery cooling becomes a priority) and you only know because airflow is nonexistent. but you turn a/c off for 5 minutes and suddenly it's all back.

Servicecenters are very familiar with this problem so you can talk to them and they know the drill about hte sensors going bad.
 

dudeabides

Member
Aug 27, 2020
28
115
Traverse City
I’ve been having the same issue with a 2020 MX LR+. It’s really just an issue drives over 15-20 minutes The a/c will work fine for about 15 minutes and then, gradually, I’ll notice it’s not keeping up. The cabin starts to warm, and eventually almost no air flow is coming out of the vents, even at max fan speed. My workaround, on long drives, has been to switch the a/c off when this happens, and leave the fan speed on high. Within 2 or 3 minutes the airflow is back to normal, and I can switch the a/c back on and then the cycle repeats. That seems consistent with a freezing evaporator coil.

I’ve been to the service center multiple times. First they diagnosed it with low coolant. So, they refilled the coolant and added dye to help find the leak. Short after that the problem returned. I took it back in and they couldn't find a leak, but then tell me that’s it is overfilled with coolant. So, they corrected that, but the problem remains. I have an appointment to bring it in again. Very frustrating. I will mention the possibility of a bad temp sensor, or failed expansion or control valve.
 
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mongo

Well-Known Member
May 3, 2017
13,448
41,942
Michigan
I’ve been having the same issue with a 2020 MX LR+. It’s really just an issue drives over 15-20 minutes The a/c will work fine for about 15 minutes and then, gradually, I’ll notice it’s not keeping up. The cabin starts to warm, and eventually almost no air flow is coming out of the vents, even at max fan speed. My workaround, on long drives, has been to switch the a/c off when this happens, and leave the fan speed on high. Within 2 or 3 minutes the airflow is back to normal, and I can switch the a/c back on and then the cycle repeats. That seems consistent with a freezing evaporator coil.

I’ve been to the service center multiple times. First they diagnosed it with low coolant. So, they refilled the coolant and added dye to help find the leak. Short after that the problem returned. I took it back in and they couldn't find a leak, but then tell me that’s it is overfilled with coolant. So, they corrected that, but the problem remains. I have an appointment to bring it in again. Very frustrating. I will mention the possibility of a bad temp sensor, or failed expansion or control valve.
By coolant, did you mean refrigerant?
If (over)filling didn't help, then thermal expansion valve or temp sensor seem like the issue.
Some of @verygreen's other posts on the subject:
There seems to be a somewhat widespread issue with bad evaporator temperature sensors in X cars of recent vintage (according to SC technician I spoke with). I just had mine replaced.

The telltale (if you don't have developer mode access) is even if you increase airflow to 11, there's barely any. The car thinks the evaporator froze and enables evaporator freeze protection (Without telling you!)

The workaround I heard about is to basically turn off A/C but leave ventilation on full blast for some time.

This is a known problem on those cars caused by a faulty evaporator temp sensor getting stuck at some wrong temperature causing freeze protection to kick in. Of course Tesla decided that this vital bit of information "A/C operation degraded because evaporator is frozen" is not worthy to show not just to owners but also to service techs. There's a bulletin and all service centers know how to fix it though so schedule the service now.

There's a workaorund where you turn off a/c and keep just the fan or turn on heat for 5 minutes or so and the condition clears temporarily.
 

mswlogo

Well-Known Member
Aug 27, 2018
6,160
5,318
MA, NH
OP here. I indeed have a 5-seater, and until reading the responses in this thread, had no idea there were HVAC system differences based on seat configuration. That's good information to have, but I don't think that's been an issue for me in general. I've driven it all summer in very hot weather (like 120F) and in general not had cooling problems that I wouldn't expect in any car being operated in those conditions. I have 30,000 miles on the car, and maybe 10 of those miles had more than 2 people in the cabin. Also, having lived with the 5-seat configuration, if I had it to do over, I don't think I'd get a 7-seater: although the extra HVAC capacity sounds alluring, I think I value the extra cargo space more.

Also, I am aware of the "battery pack cooling takes precedence over cabin cooling" situation, and have experienced that before on an occasion or two. As others have already pointed out, the symptoms of that are different than what I'm reporting here: that situation results in normal airflow but not cold air blowing, whereas what I'm talking about in this thread is cold air blowing but not very fast, despite the blower motor sounding like it's on 11.

At this point, I'm somewhat convinced that a freeze-up of the evaporator coil was my problem. I'm surprised more people haven't had this happen, but I may have just had a rare set of circumstances that day. I'm also surprised that Tesla telephone support didn't seem to know anything about it. Their solution was a) try a reboot, and b) bring it in if that doesn't fix it. If this were at all common, I would expect them to suggest letting it sit for a few hours and see if it goes away, as I think they'd want to discourage people bringing cars in when not necessary. Maybe implicit in the situation is that I'd have the good sense to not do so if the problem only happened once and went away on its own, which is exactly what happened.

Thanks all for your input.
Now that you put it that way you might be right about the freeze up.

7 seat has the same “cargo area” as the 5 seat. Everything folds flat. You just don’t get a second storage bin (under the floor) in the 7 seat. I don’t even fill the one storage bin I have. And nothing in the frunk. So another storage bin under the floor and not the easiest to get to, is fairly useless. So no regrets getting the 7 seater.

Also I have dogs that I keep in the back and having cooling back there, direct, is nice. You can also set that temp independently.
 

scottf200

Active Member
Feb 3, 2013
4,216
4,049
Chicagoland ModelX S603
It is interesting that the diagnostics screen on my 6 seater X show 2 HVACs (Aux HVAC being the 2nd) but only 1 'Refrigernet Loop' section.
Diagnostic screen = 2021.24.4 - dynotest -- mentioned in various threads. ie. Model Y 82kW Battery Pack

LeWcy93.jpg
 
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