Radiator fans don't run

[Electro-Artist]

The fans that pull air through the air-conditioning condenser no longer run on my 2011 Roadster. The compressor runs and the condenser coils get hot but the fans never come on. Does anyone have any suggestions to troubleshoot this. The fuse is okay and the fan blades are free to turn.

 

[X.l.r.8]

They are 12v so I would hook them up to an external 12v to make sure the motors are working.

 

[ML Auto]

Check the high pressure reading from the HVAC in the diagnostic screen. The fans come on around 15 BAR. If the pressure goes past 17 BAR you probably have a bad high voltage controller. The fuse on the fan circuit is on the power lead going to the controller, so any high current or short has to go through the high voltage controller. That is assuming the fans work and the wiring is good.

 

[Electro-Artist]

Thanks for the suggestions. I will follow those leads today.

 

[Electro-Artist]

I took a look at the HVAC diagnostic screen. See attached pics. The top one is while running, the bottom one was prior to starting the compressor. After running for a few minutes it slowly rose to 8.6 bar. This would seem to be the reason the fans don't run if 15 bar is required. I thought it very curious that the indicated current was 2 amps before running the compressor and still 2 amps when the compressor was running.

The compressor does seem to be working to a degree since the condenser does get warm and if one waits long enough the air from the vents is slightly cool. It would seem that a refrigerant recharge might be the answer. Can most A/C service shops deal with the roadster or does it require a specialist?

 

[X.l.r.8]

My fans ran even with low/no refrigerant. But it does look less than optimal, hopefully a top up will have to running again.
nothing special about roadster AC, R134a
In my notes I have 175 psi high, 30 psi low, so 12 bar and 2 bar. ?
Did you check the fans actually work?

 

[gregd]

My fans ran even with low/no refrigerant. But it does look less than optimal, hopefully a top up will have to running again.
nothing special about roadster AC, R134a
In my notes I have 175 psi high, 30 psi low, so 12 bar and 2 bar. ?
Did you check the fans actually work?

I thought there was a special lubricant or something, due to the electric compressor. It would be awesome to go somewhere other than Tesla for the A/C maintenance. It's about the only part of the yearly maintenance that had me stopped from doing the whole thing myself.

 

[ML Auto]

You are low on refrigerant. Any shop can handle the A/C recharge, you only have to make sure they use the correct oil if they do any repairs. You probably have a leak.

 

[Electro-Artist]

I have checked the fans and they do run when powered directly with 12 VDC.

At this point I am ready to proceed with the refrigerant re-charge. The local shop will include dye so that leak checking can be done afterwards. As I understand it the oil does not leak out with the 134a refrigerant so it is not necessary to add the special oil if nothing is disassembled. Not sure if this is correct so comments are welcome. At this point the only thing that I seem to be missing is what the correct low side and high side pressures are. I have spent some time with the Tesla manual but no success there yet. The shop says 150 psi to 250 psi on the high side and 30 - 35 psi on the low side would be typical. gregd's numbers 175 / 30 psi fit into this range but 175 (12 bar) would be too low to turn on the fans if they come on at 15 bar. Since 15 bar is about 218 psi it would seem the high side number is above this.

Any information regarding a part number for the correct oil would be appreciated in case it is needed. Thanks to all.

 

[ML Auto]

Your pressure readings show that your system is almost empty, so you probably have a large leak. A partial charge and a leak sniffer should be used. Dyes are for small seeping leaks. Any dye would have to be compatible with the electric compressor, since they are usually mixed with oil. Adding dye usually adds more oil than is needed and reduces efficiency, so try to avoid it. Your system uses POE (polyolester) oil which is also used by most hybrids with an electric compressor. Other oils can break down the insulation on the motor windings and short them out. So make sure the shop has experience with hybrids.

The pressure readings you quote are operating pressures, which very greatly with outside temp. You should always have around 6 bar residual pressure with the system off. 15 bar refrigerant pressure equates to around 140 'F so the fans aren't needed much below that. The fans come on first at a low speed (at a lower pressure), but go on high around 15 bar give or take. While driving they are usually off completely.

 

[Electro-Artist]

Thanks for the information it is greatly appreciated. I will let you know how the A/C service works out.

 

[Electro-Artist]

As promised, this is what was found. The system was charged with refrigerant and checked for leaks. A slight leak was found at the service connection. The tech used a tool to loosen and re-tighten the internals of the valve and the leak stopped. This looked like the common Schrader Valve used in tires. Not sure if it is the same but it is the same basic design.

I have been monitoring the static system pressure for over two months now. The pressure goes up and down with temperature but the reading at 25C remains constant at about 5.3 bar. There is no leak now.

No idea why the service valve would start leaking without being disturbed during the life of the car but it seems this was the issue. All has been working fine since the re-charge so I will call this a closed issue. Thanks again for the diagnostic help.