I did some limited experimenting with the a/c the other day, and on my 2001 TTRQ, which does not have the "JB Roadster Open-Roof Fan Switch Mod"(tm), it seems that if I start the car on a hot day with roof down and a/c on, the fan starts at max speed and then reduces down to roughly half speed (and probably doesn't go above that afterwards, just as you were describing).

But... if I use the manual overrides to set the fan speed higher, it does speed up. Or, if I turn the temperature down some distance (say from 70F down to 65F or so), then fan automatically speeds up as the system tries to achieve this considerably lower temperature. After turning the temp down, I pressed the Auto button, in case being in automatic mode has anything to do with it, but the fan speed stayed up high. I didn't try the experiments over an extended period of time to see if the system did anything different after running for a while.

So, although I didn't do exhaustive tests, it seems that your switch override trick may not be necessary after all? I don't know if all TTRs behave the same way or not... but if I can manually set high fan speed, no need for calling "Triangle Man" to the rescue, I guess...

BTW, after some thought, it makes some sense to me that the default automatic mode should apply some limits to the heater or a/c when the roof is down. If you think about it, the odds are pretty good that the car won't usually be able to achieve the desired temperature setting if it's hot or cold out and the roof is down, without really trying hard (e.g., running fan at max speed all the time). It all depends on the outside temp, the location of the interior temp. sensor, driving speed, windows up/down, etc., but if it's 90F outside, I doubt the car can ever get the cockpit down to 70F with the roof off. So my guess is the fan speed is limited in Auto mode as a way of applying some sort of sanity to what is a somewhat hopeless situation (i.e., the car probably can't ever achieve what the temperature setting is asking it to do). After all, you probably don't want to be running max fan speed all the time - maybe just for a little bit, until you warm up/cool down...

So, if you do want max fan speed with roof down, just bump it up manually.

Comments?

 

I'll try this, but I still think there is a diff.

 

I want to try some more experiments too... will report...