We are towing a
[email protected] 320. After about an hour of towing, especially uphill, our indicator goes from blue to red. Sometimes it goes back to blue when braking or stopping. We have only had one significant tow, we are now on our return trip home, and it is doing it again. Also, we have to manually put the car in tow mode, as it does not automatically do so when connected to the hitch. Anyone experience this?:
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However, still need to manually turn tow mode on from console. It does not automatically when connected to hitch.
As for my new Model Y (2021) it does turn on automatically when the 7 pin is connected, but it's also connected to a travel trailer that comes standard with a 7 pin.
As for what Trailer Mode does... among other things, it supplies power to the 7pin. Your running/brake lights on the trailer won't work without it. Also autopilot/auto-steer is disabled. Traffic aware cruise control will still work. I imagine it also ignores data from the rear facing cameras, since the trailer would likely confuse it. This is why some autopilot features are disabled too. Also, I think the vehicle optimizes power, traction control and other driving dynamics to compensate for the trailer.
As for the Red icon problem, I noticed that on my Model Y it switches from Blue to Red randomly. Now the manual explains that the Model Y senses a faulty electrical connection and that some or all of the lights may not be working on the trailer. But both my Model Y and travel trailer are brand spanking new so I don't think it's a faulty connection. HOWEVER, I remember reading somewhere (or someone told me) that the icon might also turn Red if the trailer is drawing too much power from the car. This actually makes sense in my case. If I'm parked and the Model Y lights are off, then I always see a blue icon, but when I turn on the parking lights (or headlights) which supplies power to the trailer making it's lights come on too, I sometimes get a Red icon. However if I'm plugged into shore power, the light will stay blue. I'm assuming cause the systems are pulling power from AC and not the trailer connector. Sure, the running lights are likely still powered from the 7 pin, but your trailer can also use power from the 7 pin to charge its battery or run other stuff. It's easy to imagine this could draw too much power. And it explains why it goes on and off, as the battery goes between charge and float, or as other things in the trailer turn on and off, like fridge, fans, etc.
I also noticed that the icon typically isn't Red during the day (even though shore power to the trailer is unplugged) and I think that's because my solar is charging the trailer battery instead of relying on the 7 pin to do it.
Anyway, do some tests around that theory and see what you get.