Ambient temperature is not everything, but the fact that you running your miner in a 12 degree Celsius and a chip on that miner gets to 86 Celsius it only means that you have poor cooling , it's either the miner's fan run on very low rpm , or you are just not getting rid of the hot air fast enough.
For starters, set the fans at high rpm , 90% is good if noise is not an issue, also please tell us more about the cooling , where does the hot air that get's blown out the miner goes to? how clean is the miner's heatsinks ? if your garage is full of dust and the miner manages to take all that inside but never exhaust it, then even running the miner in 0 ambient can't make it run cool enough.
Good point. I bought the unit used, and I should probably give it a thorough cleaning just in case. I have an exhaust shroud on the back to a 6" duct, which vents directly outside. I could adjust its location to make the duct run shorter with less bends.