MobileClimate
Member
What are the sensor readings during a thermal test in service mode ? You should see all valves working. And one more thing what’s the power train temperatures ?
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AC Compressor theory of operation?
- Thread starter geordi
- Start date
I will try to narrate the pictures but the temperature screen was while super charging. I marked the headers of two of the pictures for super charging. While driving the chiller bypass reading is the same as it was while super charging, I have not seen that change. I don’t know what that means. The coolant inlet temperatures seem to be stuck at -40, I don’t know if that’s a program glitch or if there’s something wrong with the sensors.
While driving I did notice that the compressor power would go to zero if I turned off the compressor, that makes total sense. When it came back on it was 400w/500w/600w…. Yet without any changes to the cooling system demand, it would vary between 1200w and 600 or 900 while driving.
An interesting thing that I noticed was that the refrigerant pressure did not go back up to static 100psi / 6.5 bar like I would have expected. It was slowly increasing with the compressor off but just as slowly coming back down with the compressor on. The evaporator temperature seems to be hovering in the 40s which is fine, the efficiency is there but if I increase the fan speed to four or more, the compressor starts drawing significantly more power without any obvious reason.
Adding photos while using my phone is painful. I will try but I apologize if these end up being giant I can’t seem to adjust the size.
While driving I did notice that the compressor power would go to zero if I turned off the compressor, that makes total sense. When it came back on it was 400w/500w/600w…. Yet without any changes to the cooling system demand, it would vary between 1200w and 600 or 900 while driving.
An interesting thing that I noticed was that the refrigerant pressure did not go back up to static 100psi / 6.5 bar like I would have expected. It was slowly increasing with the compressor off but just as slowly coming back down with the compressor on. The evaporator temperature seems to be hovering in the 40s which is fine, the efficiency is there but if I increase the fan speed to four or more, the compressor starts drawing significantly more power without any obvious reason.
Adding photos while using my phone is painful. I will try but I apologize if these end up being giant I can’t seem to adjust the size.
I ran another thermal test and still got a failure of a temperature sensor but it does not tell me which one which is not very helpful
During the thermal test I saw the suction temperature dropped down to 65° which is odd considering that it is 81° outside. I don’t understand, I feel like it’s acting like there’s some sort of restriction in the refrigerant system which is causing the compressor to draw too much power. I don’t want to replace the compressor because it’s incredibly expensive and the air conditioning seems to be working great but it’s just drying too much power.
Of course the service droids at Tesla will simply want to replace the entire air conditioning system because hey, it’s not their money they’re spending.
I will have to post a link to the screen recording of the thermal test.
u.pcloud.link
There is the thermal test video. If the coolant temperature sensors are what is causing the error, that’s got to be something new because I did not have a temperature sensor error before. But I don’t have anything in the service screen complaining about that.
Since leaving the supercharger after doing that thermal test, the compressor has been holding at a steady 800 W and the evaporator has been steady at 36° with 2.4 bar suction and 94 degrees suction temp.
I’m still not sure what to make of this.
During the thermal test I saw the suction temperature dropped down to 65° which is odd considering that it is 81° outside. I don’t understand, I feel like it’s acting like there’s some sort of restriction in the refrigerant system which is causing the compressor to draw too much power. I don’t want to replace the compressor because it’s incredibly expensive and the air conditioning seems to be working great but it’s just drying too much power.
Of course the service droids at Tesla will simply want to replace the entire air conditioning system because hey, it’s not their money they’re spending.
I will have to post a link to the screen recording of the thermal test.
2023-10-22 17-34-47.mp4 - Shared with pCloud
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There is the thermal test video. If the coolant temperature sensors are what is causing the error, that’s got to be something new because I did not have a temperature sensor error before. But I don’t have anything in the service screen complaining about that.
Since leaving the supercharger after doing that thermal test, the compressor has been holding at a steady 800 W and the evaporator has been steady at 36° with 2.4 bar suction and 94 degrees suction temp.
I’m still not sure what to make of this.
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After leaving another supercharger the vent temperature was extremely cold feeling and was reading 36 again but interestingly, the compressor was actually wandering between 500 W, 100 W and zero. I hate the idea that this might actually be a compressor issue… but I’m also not convinced. Is there a separate loop from the compressor to something that the battery has access to? While supercharging the compressor ramped up and the refrigerant temperatures changed, the suction pressure dropped to 30 pounds or so, while the evaporator temperature remained exactly the same. if there is some sort of diversion valve, maybe that’s related to this.
brainhouston
Active Member
Not sure how it diverts cooling but that function is for sure there.
HV battery cooling takes priority over cabin
Many ppl posted about decreased cabin cooling during SC and hot outside temps but i do believe u get a message on the screen when that happens...
HV battery cooling takes priority over cabin
Many ppl posted about decreased cabin cooling during SC and hot outside temps but i do believe u get a message on the screen when that happens...
I’ve used the parts catalog while looking at this because they have explosion images of the different systems and it does not appear obvious where diversion valves or another coil might be. But then they also don’t have the evaporator temperature sensor listed with a location either.
I am well familiar with the reduction message when supercharging. But even just a few minutes ago at night when it is in the 70s out, the car seems to have diverted the compressor such that the evaporator temperature went up into the 60s and this was after I was done charging. Something is definitely going on. The diversion may actually be within the compressor itself.
That charging was also only at 60 K, even now I am at another supercharger and charging at more than double (155k) and the air conditioner is freezing me out. I left the slow one because it was going so terribly slow and then someone plugged in next to me and it went even worse. But I feel like that was more of a problem with the location then with anything in my car. I think the problem is with the diversion system because I can see the compressor running and yet the evaporator temperature goes up and the refrigerant suction is in a range where it should be more than capable.
I hate the thought that this is looking more and more like it’s going to be the entire compressor. Of course it’s the most expensive component.
I am well familiar with the reduction message when supercharging. But even just a few minutes ago at night when it is in the 70s out, the car seems to have diverted the compressor such that the evaporator temperature went up into the 60s and this was after I was done charging. Something is definitely going on. The diversion may actually be within the compressor itself.
That charging was also only at 60 K, even now I am at another supercharger and charging at more than double (155k) and the air conditioner is freezing me out. I left the slow one because it was going so terribly slow and then someone plugged in next to me and it went even worse. But I feel like that was more of a problem with the location then with anything in my car. I think the problem is with the diversion system because I can see the compressor running and yet the evaporator temperature goes up and the refrigerant suction is in a range where it should be more than capable.
I hate the thought that this is looking more and more like it’s going to be the entire compressor. Of course it’s the most expensive component.
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Just now, when it wasn’t cooling the interior, do you see anything obvious in the temperature readings to say where the refrigerant was going or why it was drawing so much power but not cooling?
Looks like it’s probably going to end up being the compressor. I left the car alone while I was inside of a restaurant and everything should’ve been powered off… And I come back out, I have an error message to saying that the compressor is overheated and air conditioning performance and supercharging are reduced. Well I guess “off” is technically a reduction from “on” even though it had been sitting there for a half an hour and could not have still been hot. Also there were no indications of anything being any hotter than the other temperature readings that I’ve already posted. I love that it has magic sensors and magic parts that aren’t listed in the service manual or in the data stream that we can access.
I had to completely hard boot the car having a powered off for more than five minutes with the Firemans loop and the 12 V completely disconnected before the stupid thing would clear the error. And now it’s colder than I would like but at least it’s working.
I suspect the problem is entirely in the diversion valve but I don’t know if that’s even a part that exists separately from the compressor. Or it’s just a temperature sensor but of course the error messages don’t say which one of the 50 that it could be. - and I haven’t had a service message about a temperature sensor.
I had to completely hard boot the car having a powered off for more than five minutes with the Firemans loop and the 12 V completely disconnected before the stupid thing would clear the error. And now it’s colder than I would like but at least it’s working.
I suspect the problem is entirely in the diversion valve but I don’t know if that’s even a part that exists separately from the compressor. Or it’s just a temperature sensor but of course the error messages don’t say which one of the 50 that it could be. - and I haven’t had a service message about a temperature sensor.
Hi @geordi ,
I really think it would be worthwhile and a time saver to confirm that your car
compressor is plumbed properly. TSB is attached below.
I would ask your Service Center for a quote, goodwill, or warranty just to check for the condition.
They may have or you may have an endoscopic camera with a display.
This would facilitate the inspection without having to tear so much of the car apart...
Please let us know what you find.
Shawn
I really think it would be worthwhile and a time saver to confirm that your car
compressor is plumbed properly. TSB is attached below.
I would ask your Service Center for a quote, goodwill, or warranty just to check for the condition.
They may have or you may have an endoscopic camera with a display.
This would facilitate the inspection without having to tear so much of the car apart...
Please let us know what you find.
Shawn
The pipes are not incorrect, so that kinda kills that idea unfortunately.
The solenoids are probably working b/c if they are all closed when the compressor is off, then that would keep the refrigerant from flowing through the three expansion valves to reduce the pressure from the high side / increase the low side pressure. I'm surprised that it has this setup, only b/c that's an interesting way to balance the needs of cooling without causing freezing when you don't need it. Cool setup.
But even though the compressor seems to be working right now, "drawing more power" and "variable performance results" would seem to be the indications of a dying compressor.
While driving home last night with temperatures in the low 70s outside, the power usage (wh/mi) at a steady state 80mph on flat ground varied from just over 400 to 540. That's nuts. The compressor was showing anywhere from 100 or 200 watts to 1200 watts to a high of 2k - all while moving and no settings changed.
The evaporator has been holding around 45 degrees, the last time it was in the 30s was the day before yesterday. ( I drove 1500 miles in the last 2 days)
Low side pressure has been variable between a low of 30 psi and a high of 70, all while the compressor is supposed to be running. Even when it was disabled by the computer and "performance reduced" (which is NONSENSE it was off) there was still a pressure differential between high and low.
The only error in the thermal test is "temperature sensors" but it doesn't tell me WHICH ONE. Both refrigerant sensors have been replaced, all others appear to be functioning. The compressor is the only common denominator, and the variable performance / high power use I'm feeling is the only issue - but not enough apparently to cause an error code. I do NOT want to wait until it fails completely and throws metal through the system. That's not a choice.
Replacing the compressor is $400 I'd rather not spend right now on a guess, but it's the only guess I have.
The solenoids are probably working b/c if they are all closed when the compressor is off, then that would keep the refrigerant from flowing through the three expansion valves to reduce the pressure from the high side / increase the low side pressure. I'm surprised that it has this setup, only b/c that's an interesting way to balance the needs of cooling without causing freezing when you don't need it. Cool setup.
But even though the compressor seems to be working right now, "drawing more power" and "variable performance results" would seem to be the indications of a dying compressor.
While driving home last night with temperatures in the low 70s outside, the power usage (wh/mi) at a steady state 80mph on flat ground varied from just over 400 to 540. That's nuts. The compressor was showing anywhere from 100 or 200 watts to 1200 watts to a high of 2k - all while moving and no settings changed.
The evaporator has been holding around 45 degrees, the last time it was in the 30s was the day before yesterday. ( I drove 1500 miles in the last 2 days)
Low side pressure has been variable between a low of 30 psi and a high of 70, all while the compressor is supposed to be running. Even when it was disabled by the computer and "performance reduced" (which is NONSENSE it was off) there was still a pressure differential between high and low.
The only error in the thermal test is "temperature sensors" but it doesn't tell me WHICH ONE. Both refrigerant sensors have been replaced, all others appear to be functioning. The compressor is the only common denominator, and the variable performance / high power use I'm feeling is the only issue - but not enough apparently to cause an error code. I do NOT want to wait until it fails completely and throws metal through the system. That's not a choice.
Replacing the compressor is $400 I'd rather not spend right now on a guess, but it's the only guess I have.
brainhouston
Active Member
i haven't studied the system extensively but i think diversion is done either by cabin expansion valve or chiller or both
Some pics from ebay, both have electronic exv:
Have u tried watching battery temp? if it sends more cooling to HV maybe u'll see it drop in temp when AC usage is high...
@brainhouston - At one of my multitude of charging stops yesterday (towing range with this power drain issue sucks butt).... I took the time to dig around the EPC parts graphics with my ipad and also on Ebay. That is where I discovered that the system actually is a loop of high pressure tubing with three different electronic expansion valves and solenoids.
I was thinking it was an actual diversion valve in the plumbing b/c that is how the hybrid Ford Escape was set up, with a "party line" liquid system that would SHUT OFF the cabin just before the orifice tube when it wanted more for the battery. Part of the reason for this stupidity was that the battery system was an air-cooled system (rather than a liquid heat exchanger) and it was permanently pulling from outside air. In the 90 degrees of Florida, this was a VERY dumb design indeed. It should have been a liquid system OR air system but only exchanging temperature with the interior, since the batteries like to be at the same temps as the people.
But that's not the Tesla system. So the theory of operation for the Tesla system seems to be that the high pressure loop comes out of the compressor and through the radiator / fan / condenser to be reduced in temperature... Then proceed in a loop to the expansion valves of the chiller (battery), front, or rear cabin systems. Any or all of these can be open as demanded by the computer, and the high pressure stands by otherwise.
In any other AC system (expansion valve or orifice tube are equivalent here) - the pressure will fairly rapidly equalize between high and low when the compressor is off. In THIS system, it would seem that the default position is solenoids-closed and the high pressure is maintained until called for by the computer opening one or more of the expansion valves.
So with that in mind.... I don't know if the expansion valves are proportional, OR if the "chiller bypass 127%" is meaningful in any way... but it would seem that the only reason for the compressor to be running is that one or more of the solenoids is open by computer command. Running harder / doing more WOULD require more compressor work, and the compressor seems unable to keep up with the demand of 100 degree hot summer days while supercharging (two definite if not all three) solenoid requests of refrigerant.
A $400 gamble on a compressor is less than Tesla would charge me (anywhere from $1600 to $6500!) so while it hurts, it doesn't hurt that much as I already have all the other tools needed to try this. If I have to then replace solenoids.... I'll be annoyed but again still cheaper than asking the Service Center to just throw parts at it with my money!
I was thinking it was an actual diversion valve in the plumbing b/c that is how the hybrid Ford Escape was set up, with a "party line" liquid system that would SHUT OFF the cabin just before the orifice tube when it wanted more for the battery. Part of the reason for this stupidity was that the battery system was an air-cooled system (rather than a liquid heat exchanger) and it was permanently pulling from outside air. In the 90 degrees of Florida, this was a VERY dumb design indeed. It should have been a liquid system OR air system but only exchanging temperature with the interior, since the batteries like to be at the same temps as the people.
But that's not the Tesla system. So the theory of operation for the Tesla system seems to be that the high pressure loop comes out of the compressor and through the radiator / fan / condenser to be reduced in temperature... Then proceed in a loop to the expansion valves of the chiller (battery), front, or rear cabin systems. Any or all of these can be open as demanded by the computer, and the high pressure stands by otherwise.
In any other AC system (expansion valve or orifice tube are equivalent here) - the pressure will fairly rapidly equalize between high and low when the compressor is off. In THIS system, it would seem that the default position is solenoids-closed and the high pressure is maintained until called for by the computer opening one or more of the expansion valves.
So with that in mind.... I don't know if the expansion valves are proportional, OR if the "chiller bypass 127%" is meaningful in any way... but it would seem that the only reason for the compressor to be running is that one or more of the solenoids is open by computer command. Running harder / doing more WOULD require more compressor work, and the compressor seems unable to keep up with the demand of 100 degree hot summer days while supercharging (two definite if not all three) solenoid requests of refrigerant.
A $400 gamble on a compressor is less than Tesla would charge me (anywhere from $1600 to $6500!) so while it hurts, it doesn't hurt that much as I already have all the other tools needed to try this. If I have to then replace solenoids.... I'll be annoyed but again still cheaper than asking the Service Center to just throw parts at it with my money!
brainhouston
Active Member
Nice explanation n it makes sense.
I did notice on my car that High side always higher than Low on any day so it lines up with what u said.
I did also heard in youtube video about scroll compressors that they wear out n have trouble creating pressure...
That could be the issue but also doesn't make sense why its intermittent...
I agree with u, swap with used compressor n figure this out, much cheaper than tesla service
Good luck.
I did notice on my car that High side always higher than Low on any day so it lines up with what u said.
I did also heard in youtube video about scroll compressors that they wear out n have trouble creating pressure...
That could be the issue but also doesn't make sense why its intermittent...
I agree with u, swap with used compressor n figure this out, much cheaper than tesla service
Good luck.
The one I have coming is a reman by R&Y, so not technically "used" but way cheaper than Tesla and less questions than Ebay.
It will be here tomorrow - I'm hoping that the result is a cold AC system with power in the sub-1kw power range.
It will be here tomorrow - I'm hoping that the result is a cold AC system with power in the sub-1kw power range.
MobileClimate
Member
That compressor is going to keep going intill it hits 35f at the evap than it cycles off .. why are you not at 34-35f. At the evap sensor ? Confirm actual temp of evap ..40 is not cold enough
Ok, even when there isn't much cooling being called for? There are times when the vent temperature is frigid, but also plenty of times when the evap temperature is registering into the 60s and it is obvious that there's no cooling happening. So is the problem the sensor (I don't think so?) or the compressor or the EXV for the cabin?
On the thermal test, the only failure has been "temperature sensors" but it doesn't say which one and there's no errors logged.
MobileClimate
Member
That compressor discharge temp is too high ..which means you have the wrong refrigerant /air in then refrigerant / or something blocking the condenser..too much refrigerant will use more power usage because the condenser fan will run more..260F is way too high that would be normal for 120F day
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No chance of air in the system, I have a proper vacuum pump and pulled it to 30 inches after 30 minutes the last time I charged it. Proper POE oil. The only extra was 1/2 ounce of dye JUST in case there was a leak - which I do not believe it has.
I'm surprised that you say the discharge temp is too high - it has to be higher than ambient or there won't be much temperature exchange with the air to offer much cooling performance. It's more about the pressures, but this program doesn't read the pressure. My service gauges on the other hand DO. High side pressure at 85/90 degrees ambient was showing 200 psi. Low was right on 30 psi. This was with the front and rear AC both on full blast. Refrigerant is clean 134a, no additives.
I'm surprised that you say the discharge temp is too high - it has to be higher than ambient or there won't be much temperature exchange with the air to offer much cooling performance. It's more about the pressures, but this program doesn't read the pressure. My service gauges on the other hand DO. High side pressure at 85/90 degrees ambient was showing 200 psi. Low was right on 30 psi. This was with the front and rear AC both on full blast. Refrigerant is clean 134a, no additives.
