Low Temp T-Stat = Colder Heaters in Winter?

Hey guys, Now that it’s cold out and dipping to freezing, the heater is basically cranked all the time. My 911 has a low-temp thermostat from the PO, and I also have a same-year 986 Boxster. The Boxster’s heat is noticeably warmer. I can’t help but blame the t-stat, because the 911 visibly runs cooler on the gauge. On a cold day, if the 911 gets stuck in traffic, the temp will creep up to just right of center (about 1 o’clock / “normal”). When it does that, the heater suddenly blows much hotter. But when I’m cruising, it likes to sit just left of center (around 11 o’clock), and the heat drops off. The 986, on the other hand, sits at 1 o’clock year-round, summer and winter, and the heater is consistently hotter. So I’m really leaning toward the thermostat being the difference. I’ve talked about this before and some people said colder engines are always better for longevity, and that the stock, hotter t-stat is more about emissions, keeping temps up around 100–110�C so it burns cleaner or whatever. All I know is: In summer, when I tested it, the 911’s heater was like a campfire. In winter, it feels more like an old house with weak radiators. If I’m in stop-and-go traffic for 30+ minutes, it eventually gets toasty, but once I’m back on the highway, kiss the real heat goodbye. Heat level is directly linked to coolant temp (no duh but yes) At this point I’m seriously thinking about swapping back to a stock thermostat, and also adding heated seats. A set of heated sport backs would be amazing, but I’d even be happy with a really well-made heated seat cover. Curious what you guys think... anyone run into the same thing with low-temp t-stats and weak heat?

I�ve run a low temp thermostat for over 10 years with zero heat issues. My bet would be that the foam covering your HVAC blend door is gone.

If it's a 161 degree thermostat, for example, the water temp is going to be at least 161 degrees once the engine warms up and the thermostat is opened. Prior to that the temp will be climbing from starting temp to 161 degrees. That should be plenty warm. I agree the blender door is probably deteriorated and so too much cold outside air is being brought into the car through the heater ducts.

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On a hyway trip where you seem to have this problem, could always cut a piece of cardboard to fit in front of 1 of the radiators, or half of it..? Adjust the size of the block off to suit the weather/driving conditions... jmho

I havent had any problems with heat using the LTT here in Chicago. My bet is its your blend doors. Unfortunately, its a project we will all have to do one of these days.