So just as the weather is finally getting warmer, I went out yesterday on a short (1-1.5 hour away) road trip. It wasn't super hot (about 24C/75F), but I thought using the A/C with windows shut would be better for range and no A/C with the drag of open windows.
The air blowing was just not cooler, which took a bit to be sure as blowing air feels cooler and the temperature was not super hot, but more noticeable was that the guess-o-meter did not change. Given that the system may have decided that with the outside temperature, the cabin setting may not have been an additional load on top of what it was doing for the battery and motor already. Having gone through the replacement of one of the two coolant diverter valves about six months ago, I thought that the other may be having an issue, though no wrench light came on. Not having A/C was not a problem this day, until I got to my destination and had to charge.
I planned on bringing up the SOC to about 50% on a DCFC and moving to a level 2 charger for the duration of my stay (about 2-3 hours) to fully charge for the return trip. The DCFC, rated at up to 50 kW, started off delivering 35 kw, which is not unusual for the network it is part of in my experience. But then about 10 minutes in, it started to drop an it got to 16 kW before I stopped and moved to the L2 spot. The SOC started at 26% and got to 41% before I stopped. The L2 was delivering 5.7 kw, which didn't surprise me with this same network which is what they typically deliver on an "up to 7.5 kW" unit. However, I noticed a couple of hours later it had dropped to about 4.5 kW.
When I returned and started to leave, I got a warning with the "turtle" light in the dash (first time I've seen that) indicating that performance may be limited due to a hot battery. What I was suspecting was pretty much confirmed: the compressor was not coming on. The only cooling available was the coolant circulating pump and the radiator fan.
It was getting cooler when I left and the airflow from being back on the highway must have done a half-decent job of cooling things since the guess-o-meter had my surplus to get home gradually raise from about 40 km when I started the drive to about 85 km about a half hour before getting home. It would be nice if there was a way to see battery/motor temperature on the dash - my wife's Lightning has a battery and motor temperature indications at the top of the dash display (bar style, not actual numbers).
Once home, I connected the laptop and fired up Forscan, but there were no DTCs whatsoever. I noticed it showed that the AC_PRESS_HI and AC_PRESS_LOW sensors were reporting pretty close to the same values - about 153-156 kPa for the high one, and 157-158 for the low one. I hadn't looked at these when things were working, but I suspect that the high pressure sensor should be noticeably higher than the low one.
About the only thing I have the ability to check was the functionality of the high voltage fuse for the compressor that is located with the TCM - no problems there. So, I'm guessing that either the coolant leaked out and it won't start because of that, which would not just involve getting it topped up but also finding the leak, or that the compressor itself is shot and needs replacing.
This will be going in to have it looked at, but I'm curious if anyone has any other suggestions.