Jazzrock

This morning it was about 53 degrees here in the Bay Area. I had the climate control on 75, and heat was really fast coming on. Works great. Every morning I have heat, no problem.
This afternoon, after work, it was about 62 degrees. My climate control is still set at 75 and no heat comes on. It's cold air, though not as cold
as AC. I had this issue with my MB CLA as well. In the afternoon I got no heat often times. I took it to the MB dealer and he said it was working
fine. He even charged me $195 to tell me this fine information, under warranty, saying he has to charge for the time they looked at the car.
It seems to me I'm missing something. In our 2000 Ford Taurus wagon, you turn the heat on and it puts out heat. Turn on AC, and the same.
Climate control doesn't work like this, obviously. I tried Googling this issue. Thanks!

pngo

https://www.clublexus.com/forums/is-...afternoon.html

Jazzrock

So if there it is 64 degrees outside and I set my temperature to 75, the heat will not come on because the temperature is too close for it to put any heat out?

Sasnuke

When you're judging the availability of heat in the morning and afternoon, is the vehicle at operating temperature in both instances?
And what is being used to judge outside temp.? The reading on the dash or something else.

Just trying to get an idea of the parameters you're working with to see if this is a behavior of the HVAC system, or is it an instance where a HVAC re-initialization is needed.

athanato

That's what MB does, drain your bank account.

Jazzrock

I'm using the reading on the dash, which is in the ballpark. It works great in the morning, every morning, as I said, really fast, but no real heat when things warm up some in the afternoon.
The heat comes on within a few minutes of being on the freeway in the morning, but never comes on in the afternoon.
I think I don't fully understand how the climate control functions. I turned it up to 79 in the afternoon after it was at 75 and still no heat. Isn't there a sensor in all vehicles that tells the system what the temperature inside the vehicle is? I don't know that it's not functioning properly. I'm hoping with further explanation I can understand how it works. Thanks.

JDR76

In the afternoon when it's 75 outside and you set the temp to 79, what's the temperature inside the car like? If it's 75 outside, it may be 80 inside with a little sun coming in.

You could put a small room thermometer in the car to check inside temp and compare it to what the climate control is doing. Then it's quite simple, if the climate setting is warmer than the interior temp, you should have some heat coming out. If the climate setting is cooler than the interior temp, it should be cool air coming in.

Sasnuke

The temp on the dash comes from a sensor that is mounted in the front of the vehicle...trying to reflect the ambient temp outside.
The HVAC system has it's own temp sensor inside the car, near the evaporator...basically inside the HVAC box.
So realistically the two sensors will never read the same cause in the summer sun the interior of the car can be a lot hotter than the ambient temp, and same in the winter, assuming you have the heat blasting in the winter.
Like the poster above me suggested, you really need to know what the interior temp is inside the car, so that can relate it to your temp setting.
I guess one underlying question is, when you have it set to 75 for the afternoon ride, despite not getting hot air out the vents, are you actually cold? Even though the ambient temp is 64, doesn't mean its not closer to 75 inside the car if it's been parked outside in the sun all day.
But if you are not cold, then the system providing you heat in the afternoon isn't going to help, cause you were comfortable already.

Maybe try the system on Auto mode for a few days and see how you like that.

Jazzrock

As I said, the outside temperature was 64, and I had the climate control set to 75. I will get a thermometer to see what the temperature is inside the car.

Jazzrock

I will get a thermometer to test the temperature inside the car. I was not freezing cold certainly, but a bit chilled, and wanted some heat to
warm me up. I put it on Auto for a moment and immediately got AC. It just seems if I want heat, I should be able to have it. I could park it
under a tree to trick the car into thinking it's colder outside, but then I get sap on my car. This is at the parking lot at school, where I teach.

Sasnuke

Interesting that when you put it on Auto, with the temp set to 75 it turned on the AC. Do you notice the fan speed mode at that time? Was it like max fan speed and Windshield/Foot mode.
It would have only turned on the AC if it detected the temp inside the car at above 75.

Jazzrock

I suppose I could put up my sunshade on the front windshield to bring the temperature down even further to try and get heat. I think it was on windshield/foot mode, as that is what I had it set at in the morning. I didn't set the fan speed at max. Would setting it to Auto and the AC then coming on cause the fan speed
to go to max? I turned it off immediately. Cold it was!

Sasnuke

For Auto mode, you set the temp and the system does the rest...i find when you call for heat it will usually turn the AC on and set the fan speed to max, then it slowly backs off the fan speed, and will select the mode accordingly.
I'm not sure if having it set to Windshield/foot overrides the mode as you basically have it set to Defrost.
Just a side note...when you set the mode to Windshield or Windshield/Foot, the AC is automatically turned on regardless of the temp setting...and the AC light won't be on.
My general rule of thumb is that if you don't need to Defrost anything (like the windshield) then don't use the Windshield or Windshield/Foot mode...it unnecessarily runs the AC which could rob a little power and fuel.
In the 3IS the Windshield Defrost mode is actually a separate button, like the Rear Windshield defroster.

So step one, stop using Windshield/Foot mode...I doubt it's helping your issue here. Of course, if you need to defrost the windshield, by all means use whatever defrost mode you like until the windshield is clear.

I would agree that 64 is definitely on the cold side as I usually keep my house at 72, and if it drops to 68 everyone's whining that it's too cold. Personally for me 75 is too hot, but that's me.
And then there's 75 with 0% Humidity and 75 with 80% Humidity...which are going to be feel very different. The latter is gonna make you sweat like a fat turkey the day before Thanksgiving! lol

Jazzrock

I misspoke. I am using face/foot mode. I understand how all the controls work, just not why I can't get heat at certain times. I re read the AC portion of the manual, which is no help.
I can't find anything in it explaining heat. I think I need John Cleese to do a Monty Python type explanation. I'm just sure that would clear everything up.
"There's nothing wrong with you that an expensive operation can't prolong."