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Roadster HVAC Overheating Problems

Anyone ideas on that topic:

When switching on the air condition in my Roadster (1.5 but at least some parts if not all of the HVAC are 2.0/2.5 series parts) the two front fans won't start to turn.
Another Roadster I could examine was running the front condenser fans immediatley after switching on AC.
During inspection this summer (I bought the car this year) the mechanic said they wouldn't have to start immediatley (but I thing he wasn't right about that...)

I cant really say if the AC compressor is running (how loud is it, is it noticeable when front fans are off / on ?) :confused:
This could lead me to a more specific failure like whole set is not getting a start signal or current to run or theres only a problem to the fans or their relays...

If battery gets to warm normally the AC of the HVAC is used for cooling down and the front fans should run, too
this never happened to me eventhough in debug screen HVAC a 100% cooling was requested by the system.

I checked the HVAC solenoid valves (for evaporator and chiller) in debug mode and both are clicking, also being able switching on / off cooling pump of the battery.
Fuses are all good... F... I really was looking just having to replace a blown fuse... :cursing:

Heater System and cabin blower are ok, too

Fans and power connectors of the two fans in front seem to be ok, too.

So... what can I check else?
I might want to change the HVAC Fan Control Module (anyone done that before? is it a standard module or a Tesla part?)
Technical manual says it is located RH inner wing under the hood. Where's that really?

OK... if you have any hints or suggestions... would be awesome!


VIN EU ... 000112
Upvote 0
You need to specify what temp your ESS was. If you don't cross the cooling threshold where its cool enough, only the HVAC will kick on and the fan's won't and this is perfectly normal. If your ESS is 30C+, say 35F, your fans should absolutely kick on as long as you're charging from a 240V source and 12Amps+.

When the condenser kicks on, its has a distinctive low audible hum. If the VDS indicated that 100% HVAC cooling was requested and was indicated to be on, then I'm certain it was running.

Again, I'd get the ESS temps at 30+F then place the Roadster on a 240v / 16amp + charge. Within 5 mins the fans should be running. If not, then start debugging from the fan harness connector back to ensure you're getting the proper voltage to the fans.
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It could be the A/C system is just low on refrigerant, as the system shuts off when it is low. You can read the pressure from the HVAC screen.

Right, and the HVAC system is trying to ramp up the cooling but it never succeeds from the diags hvac status output. Also the fan's won't kick on if the hvac request wasn't successful.

"HVAC said 100% requested but 0% received"

I'd suspect that the VDS screen would be alerting the user about low charge pressure. Mine does if temps drop, so whenever the hvac pressure drops below a given threshold I get an alert. I do run in debug all the time, not sure if that's a debug only message.

Curious if the ESS drops by any degree, most likely nothing really gets cooled at all.
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ML Auto

Mar 8, 2014
SW Florida
HVAC coolant pressure is ok (31.8 Bar)

You definitely have a pressure problem or a disconnected/bad pressure switch. My track car has no A/C and reads the same 31.8 Bar, which is about 467 PSI-way to high. I would check the refrigerant with an A/C gauge to see what the actual pressure is. I believe the reading defaults to 31.8 when the system is empty.
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so today I removed the covers under the front hood to get direct access to the pressure transducer (still showing the 31.8 atm, sometimes for a short moment going to 0.0 atm shortly after having the car parked). When I unplug the sensor I get a warning over VDS; so connection seems to be ok. From a fellow Roadster driver I got the data that normal pressure is about 8-9 atm (this is normal for AC systems, counterchecked with a mechanic - he didnt want to take a look on the Roadster cause of the 400V... hahaha... I'm way beyond that pal.... :D )
So: anyone ever changed the pressure transducer by himself? anyone being able to provide a part number for it?
As I can see from papers there is a isolation ring beneath the transducer itself so it could be exchangeable withouth causing a leckage....

PS: more and more I get to know this car and it's great - I don't regret a single second of 8 hours cleaning rear fans, PEM and motor fins.... :D


May 13, 2014
My A/C stopped working last summer because the compressor was empty. After Tesla had filled it up it was ok again. Next week is my last service under warranty, but it is too cold in Norway at the moment to check if the A/C is working. How can I check if the compressor pressure is ok before the warranty runs out?


Sep 17, 2013
Exchanged the HVAC Pressure Conducter, still get the VDS 31.2 Bar... :/
Exchanged the 400 DC/DC control unit with a spare unit... still no change in values or working HVAC system...

anyone of you guys got another idea what I could check or replace?

When I was playing around with the ESS Sheets temp sensors during a really hot summer, if I kept one sheet temp sensors colder than the rest say at 55F, even if the 10 other battery sheets were hot like >105F the HVAC would never kick on to cool the ESS. Then when I dialed the tempature pot back up to match the rest of the pack then the HVAC would kick in.

If I was you I would ask a service center tech to look at your ESS sheet battery temperatures. Might have one sheet that is stuck which would be odd.. as I think they would just fail either open or short. Also I'm guessing they could do a simple test where they could force the car to turn on the ESS cooling to test it out, this would cover the scenarios if you have any mechanical issues.

Here are some hints and clues concerning the HVAC system of the Roadster and the given values in service menu:

after a long journey and a SC which wanted to sell me a DC/DC System for 800 Euro (even a bit more) to deal with my concerns I found out the following:

if the HVAC system contains no or in my case only a left over of 50g of liquid coolant the service menu will show a value of 31.8 Bar (which is ridiculous high) - I exchanged the measurement sensor and still given the same value (only connected a replacement sensor, not connected to the high pressure pipe)

I exchanged the DC/DC converter in the front (responsible for the HVAC and heating system of the cabin, HVAC is also used over a heat exchanger for cooling down the coolant of the battery) - thats why the front fans and HVAC compressor sometimes kick in while charging or giving the battery a hard time burning some rubber ;)

I went to a garage which allowed me to use their equipment for HVAC maintenance. Most garages make a denial when you mention the 400 Volt :D :D ;)

While sucking the 50g leftover coolant out of the pipes the measurement of the HVAC went from the default value 31.8 Bar to 0.
Ater a 20 minute vacuum of the HVAC (leckage check) and no air coming into it I was able to refill the system with 750g of refigerant coolant.
Value went from 0 to 3.0 Bar.
Immediately after the filling was done and the HVAC was started the compressor would start to run and pressure would go up to 19.8 Bar.
Since then (a few days now) HVAC is working fine and when cooling of battery fluid is requested the HVAC woould start to run,

Conclusion and remarks:

My SC wasnt able to determine that there was almost no coolant refigerant fluid in my HVAC system anymore (guys that's a no go and I will have a talk about that in the SC in the next weeks for sure!) THIS IS PART of the maintenance plan!!!

They wanted to exchange the DC/DC converter in the front (which is often a cause for problems due to moisture problems - I have to admit) for quite a few bugs (btw. I counterchecked with a used one... :p and got the same values and behaviour of the car)

nowhere is mentioned that the pressure sensor of the HVAC will show value 31.8 Bar when theres (almost) nothing in the HVAC anymore.
SC didn't know that front fans have to kick in after starting HVAC for cabin in a few second (also when cooling is requested by the system for the battery)

Raodster is holding pressure at about 4.8 Bar since I filled it up... and the best: filling up cost me 80 bugs and a few bugs for the mechanic who helped me...

BTW: you might check the website of Eberspächer in Germany and be astonished how many standard parts of them are used in the Roadster ;)
what is the right level of bar for the Prefigerant ?
When filling up with 750g (Roadster 2.0 / 2.5) level went up to 3.0 3.2 atm (it depends also on outside temperature!)
during driving (no HVAC operation) its between 3.2 up to 4.8 (depending on outside temp)
during operation it will go up to 18 / 19 atm depending on rpm of compressor.
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early member
Dec 13, 2014
When filling up with 750g (Roadster 2.0 / 2.5) level went up to 3.0 3.2 atm (it depends also on outside temperature!)
during driving (no HVAC operation) its between 3.2 up to 4.8 (depending on outside temp)
during operation it will go up to 18 / 19 atm depending on rpm of compressor.

Thanks Daniel !

Had my yearly service done two weeks ago, but they overfilled my HVAC - again - resulting in continious " HVAC compressor over Temp messages"
Went back yesterday to get this fixed -the sc technician made a testride an said that motor and temperature were fine - so I had to explain him that the hvac had nothing to do with pem and motor temps- but with battery cooling.
After removing some hvac liquid the car was charging fine in SC.
But when i charged again at home later , again "HVAC compressor overtemp" error.
So I let out some more freon our of the hvac using via the valves. ( after seeing a youtube video on how to do this )
Et voila - issue solved.
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  • Informative
Reactions: Rolf68


Active Member
Jun 7, 2011
I just started getting the "HVAC compressor over-temp" message. Also an over-pressure message. It only happens when charging, not when running the AC for the cabin. It must be a different reason than being over-filled. I haven't touched the system in over a year and neither has Tesla. These are debug messages and the car continues to charge. Any idea what might be causing this? A crimped tube?


Active Member
Jun 7, 2011
It sounds like the condenser might be dirty. You can backflush it thru the cooling fans. All the crap that goes thru the front grill ends up stuck in there. The Compressor runs at full speed when charging (6000 RPM) and only about half that when on high A/C, so the temps and pressure are higher when charging.
MLAUTO I hereby nominate you as the MVP of the Roadster forum. Thanks for this idea which will enable me to stop scratching my head for a few days (or longer) while I check this out. I wonder what's the best way to backflush the condenser - water or air or shop vac through the grill. Or all three.
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