2011 Justa, Manual. ~107k.
I usually don't use the heat that blows towards the cabin. Only usually use defrost and/or floor heat .My commute doesn't usually have very many places where I idle, so I have no idea how long this has been happening.
I happened to take it out to grab some food which I never so, but while I was sitting waiting doe the food in the drive thru, I turned the heat towards the cabin and it was cold. As I pulled off, it immediately got quite hot as expected. Stopped again and within 10 seconds it was back to cool again.

One other thing I noticed is that when I slow down, push in clutch, idle, etc. the RPMs, of course, drop but there is also a very noticable drop in air speed of the heat. I do notice this also happens in the summer with the AC and is most noticable when on full power. I know it's a little normal in manuals for this to happen so didn't think too much of it.

Also, I had seen a couple of CELs related to the thermostat stuck open; however, after a few drives, the light goes off. I actually have the OEM thermostat replacement, but it's been really cold and rainy on all the weekends and I don't have a garage so haven't changed it yet. I figured worst case if it is stuck open that it just wouldn't best up as fast, though I will say that actually doesn't seem to be an issue when driving. I also have the OEM antifreeze to flush it all out when I change the thermostat because at some point it was changed and has the green stuff in it.

No other issues/symptoms to speak of and it runs great otherwise. Any ideas?

 

For the cold-hot issue, could be low on coolant, partially plugged heater core, or maybe water pump vanes are corroded.

If the thermostat was bad, like stuck open or even missing, you may never get hot water to the heater

Slowed fan speed could be an alternator on it's way out

I use the green coolant in all my cars, including both Mini's

Bryan

 

You'll need a scanner or a scan gauge to determine what your coolant temperature is. You can pick up a Foxwell NT510 or 520 for a good price by contacting Elly@foxwelltech.com. Tell her that you connected with me on the MINI Forum, and you'll get a very good price!

Normal coolant temperature is 221 deg F.

If the blend air door or the blend air door servo motor has issues, this could cause the problem you are experiencing. Also, the temperature control on the instrument panel could be the problem, Again, the Foxwell scanner can pull up the percentage of travel of the blend air door servo motor. At full cold you should see 8% on the scanner; at full hot, you should see 100% on the scanner.

As far as fan speed, if you see a drop in fan speed when you go to idle, I would check to see what your charging system is doing. My car charges at 14 volts when I'm at idle, and that goes up or down slightly depending on the state of charge of the battery.

 

I looked again and it is actually the blue stuff. Not sure why i thought I had seen green previously. I have some of the proper blue stuff. I checked the level and it was below the MIN line, but not really by much. I filled all the way up to max and drove in this AM and it seems to have resolved the problem. Strange such a small amount would cause such a drastic difference, but it seems to have. Now crossing fingers as I check next week that it hasn't dropped, indicating some other issues. I don't see any leaks that are obvious, so I suppose it is possible it is head gasket, but oil looks clean, so not sure. Maybe there was air last time someone change the fluid (it was pre-owned when I purchased it) and it worked itself out but took a long time. Who knows. Hopefully just a fluke.

I already have a scanner, but thanks for the offer. It was below freezing this morning and all my speed is highway 60 mph+. I watched the coolant temp and it seemed to be operating properly. Wasn't exactly 221, but was close enough at 213ish. As I mentioned above the coolant additional seemed to have corrected my problem.

As far as the blower slowing down being caused by the alternator - I know this can be a cause; however, I would also expect to see the effects of a problem like this in the lights (headlights, interior lights, etc.) and that dimming does not exist. So not sure what else it could be. I will still do some testing with a meter when it warms up a bit outside, or rather, when I can get home before it's dark! Thanks for the response!