And what do you mean by the cruise control telling me when I can or can't use it that makes no sense at all if you can't use cruise control in wet roads or rain what good is it
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I know it has autobrake because I tested it I went into town with cruise control on set at seven car lengths and it kept me seven cars away right till it stopped
My understanding from other threads is that if the weather isn't great TACC shuts off and regular (basic) cruise control isn't usable either.
Lots of stuff here that's not quite right.
First of all, according to the release notes, the TACC cruise control is not supposed to be used in heavy rain or snow. Please see the release notes for the exact language. I'm sure the rationale is that the TACC relies on radar to see the other cars around your car, and in poor visibility conditions it can't see well, so TACC is not safe.
Now that we have TACC, we no longer have the option of "regular" cruise control without it. A lot has been written here about it, and many of us would like it. The theory is that Tesla believes we would be confused, and might expect the car to keep us from hitting other cars when it no longer has control of that functionality. So better to disable all cruise control functions rather than take that chance. (I'm not saying I agree with that. I'm just stating what others have suggested is probably Tesla's rationale for disabling "regular" cruise control when TACC is disabled.)
As for TACC shutting off when the "weather isn't great", that's not what's going on. TACC shuts down when the sensors can't see what's going on. A lot of the recent issue have involved the radar unit being blocked with snow and ice. (Please see the first post in this thread.) If the radar unit can't "see" the TACC can't function, and will shut itself down. It's as simple as that.
As for the braking you (richardfallows) experienced when your TACC shut down, I don't recall exactly what happened when mine shut down, but it's possible that the car just essentially took its foot off the go pedal, resulting in sudden full regenerative braking. Again, not saying that this is good, or the proper thing for the car to do in that situation, if that is what happened. Just that that could be what happened. In which case the car was not applying the friction brakes, but rather it just stopped trying to go, so to speak.