Automatic Climate Control problems

Those are some pretty odd symptoms... I would guess that, when going up hill, less energy was available for running the heater, and the opposite was true going down hill.

For the internal temperature change... was the A/C button lit? if the A/C isn't on, i believe the car can't cool the air at all, which may be needed. Also, what time were you having this problem? In my recent road trip (minnesota to ohio and back), we noticed that the car felt a lot colder in the evening than it did during the day. The main reason for this was that we had the sun shining down on us during the day, which makes the cabin feel a lot hotter than it really is, and with it gone at night we had to turn up the heat.

For the non-repeatable events with the defroster... Very odd, and i've got no advice save this: if it's non-repeatable, it's probably not much to worry about :lol:

 

<div class='quotetop'>QUOTE(Jim Biggs @ Dec 4 2006, 08:52 AM) [snapback]357409[/snapback]</div>

Next time try AC/Auto.
As TonyPSchaefer says,"Just like the variable transmission, you can think of the A/C as a variable system. Basically, if allowed to do it's thing without human interference, it will work extremely efficiently."

 

I had a similar problem with an older Mercedes Benz. It was caused by leaks in the vacuum system that operated the opening and closing of the climate control system's duct doors. I do not know how those are operated on the Prius, though.

 

the system uses servo motors to open and close ducts.

that is unusual. were you using the steering wheel control for the defrost? or the MFD? were you using the auto a/c?

 

<div class='quotetop'>QUOTE(Jim Biggs @ Dec 4 2006, 06:10 PM) [snapback]357727[/snapback]</div>

A/C on or off is not AUTO A/C. Let the car do the work. If allowed to do it's thing without human interference, it will work extremely efficiently."

 

it's 12v- HV only runs the electric motors and the a/c compressor. if there was a power fluctuation issue you'd see all sorts of crazy stuff going on.

 

The A/C heating system will work at maintaing your set temperature ONLY if you have the A/C Auto button selected. This is the best position to maintain th etemperature the best.

 

Edit: oh

Wth​

, I didn't see that this was an old thread until after I posted.


I think the system takes into consideration:
Outdoor air temp, interior temp, engine coolant temp, target temp

I think (may not be accurate - just a guess) the logic is something like this:

If target temp is lower then outdoor air temp, then turn on air conditioning compressor (strength of air conditioning is based on the difference between target temp and interior temp).
If target temp is lower then interior air temp and higher then outdoor temp, then a/c remains off.

If target temp is greater then outdoor temp and its lower then engine coolant temp, then the engine coolant is used to warm the interior.

If target temp is greater then outdoor temp and higher then engine coolant temp then engine stays on and both electricity and coolant is fed into the cabin to make heat.

Fan speed is based on difference between interior temp and target temp.
If target temp is 2 degrees above or below the indoor temp, fan speed is increased for every 2 degrees it is above or below.

 

Not on my 2005. Maintaining temp works fine with it off, ASSUMING outside air temp is opposite what you want inside. (cooler outside than desired inside, or hotter outside than in. If you need cooling beyond the outside temp, you WILL need the AC.

 

I did notice this was a thread just over 10 yo.

I'd like to point out that while what you say is true, it does not invalidate the points Bob64 said, as this hypothesis has been establish as the way it works.

That being said, why bother with the hassle of deciding whether to have the A/C on or off. Just set the thing to AUTO and set the desired temp and let the system work it out? You will find that adjustments are required to the temp (as a persons perception to hot/cold is subjective taking into consideration the outside weather and the clothes you're wearing) and this is easily accomplished by a quick adjustment of the steering wheel buttons – 0.5 deg up or down. KISS.