RPM Jump with heat on

[Dyna]

Hello,

I tried to search for the problem I'm having with my 2014 Legacy but can't seem to find anything on it.
Since it started getting cold and the need for the heat to be on, I've noticed that when I turn the heat on, my RPM will at times sit around 2-2.2k RPM even though I'm just cruising at 40 or 45mph. I mean same happens regardless of the speed as it goes over 35mph. 
No codes are given, car doesn't feel funny, except for this. If I'm driving and I turn the heat off, the RPM will drop down to about 1.4-1.6k. If I turn the heat back on while driving, the RPM will not increase. It only happens if the heat is on and I'm taking off from a stand still. Then after a bit, RPM will drop on its own regardless of heat being on or off. 

Any help on this would be appreciated.

[GeneralDisorder]

It's because you are in defrost mode and it's running the AC compressor. The ECU decides how much RPM the compressor needs depending on temp and pressure sensors in the system. You have a CVT transmission and a DBW throttle control. If this was not as intended it would throw codes. 

GD

[Dyna]

1 hour ago, GeneralDisorder said:

It's because you are in defrost mode and it's running the AC compressor. The ECU decides how much RPM the compressor needs depending on temp and pressure sensors in the system. You have a CVT transmission and a DBW throttle control. If this was not as intended it would throw codes. 

GD

I don't think I'm in the defrost mode. I don't turn on the defrost option for the rear window and mirrors or the front windshield. AC is definitely not on. It' just "normal" heat with the temp knob set to hot and it's blowing hot air out towards passengers and feet. Unless I'm not not understanding and there is another 'defrost mode'. 

Thanks for your reply though.

[GeneralDisorder]

Have you looked to see if the AC compressor is running when this occurs? The system may not require the defrost to be selected. AC helps to dry the air making the heat more efficient. For all I know that new of a model may have humidity sensors that will elect to run it in other modes.

In any case there is NO adjustment for RPM under any condition. The system is 100% electronic. The ECU and TCU work in tandem to decide what engine RPM is applicable. If there are no warning lights or other indications of a concern from the computers on board you will just have to assume it's normal programming. And if there is a problem, no one here can help and there's nothing you can do yourself either. It would have to go to the dealership and be diagnosed with a Subaru Select Monitor (SSM). 

GD

[Dyna]

3 hours ago, GeneralDisorder said:

Have you looked to see if the AC compressor is running when this occurs? The system may not require the defrost to be selected. AC helps to dry the air making the heat more efficient. For all I know that new of a model may have humidity sensors that will elect to run it in other modes.

In any case there is NO adjustment for RPM under any condition. The system is 100% electronic. The ECU and TCU work in tandem to decide what engine RPM is applicable. If there are no warning lights or other indications of a concern from the computers on board you will just have to assume it's normal programming. And if there is a problem, no one here can help and there's nothing you can do yourself either. It would have to go to the dealership and be diagnosed with a Subaru Select Monitor (SSM). 

GD

I appreciate your responses. 

I went for a drive, picking up kids and what not, and paid extra attention to what's happening. It usually happens when I'm getting in the car for the first time in the day or if the car's been sitting for some time (temp of oils, engine, etc. has gone down). As I've stated it only happens when I turn the heat on and I couldn't really tell if the AC compressor is running when it happens. If I turn the heat off while it's happening the RPMs go down. If I turn it back on, the RPMs go back up. 
While this is happening, I moved over into manual mode and I was in 5th "gear". Shifted up into 6th, and RPMs went down to normal. So it's only happening in Auto mode. I do a lot of short distance driving, so I decided to drive a bit extra and after about 6-7 miles, while this was happening in Auto mode, the RPMs went down and after moving over into Manual mode, it was in 6th gear. 

I spent a couple of hours trying to look into this and found that many are experiencing this and it's not an issue, I suppose. They're saying that with the CVTs, in sub-optimal temps, the ECU controls the RPMs and delays shifting into the higher "gears" in order to get the RPMs up and heat up the oils and other components faster to get them into optimal operating conditions. Well, I'm not extremely versed in these things, but at least your responses and the research I've done have put my mind at ease a bit. 

Thanks again.

Edited November 29, 2018 by Dyna

[GeneralDisorder]

Yes - it would be fairly common engineering practice to increase RPM to warm engine oil and coolant. It provides cabin heat sooner which helps with faster defrost, etc. Also the oil thins out and this provides economy benefits. 

GD

[Mike104]

The more I hear about the new vehicles, I am enjoying my 03 Forester with 5MT and 99 OBW with 4EAT

[GeneralDisorder]

49 minutes ago, Mike104 said:

The more I hear about the new vehicles, I am enjoying my 03 Forester with 5MT and 99 OBW with 4EAT

You ain't kidding brother. I work on this junk every day and it makes me appreciate real non-disposable machines. All this stuff made in the last 10 years or so is COMPLETELY disposable. Subaru is already setting a trend of throwing away parts after about 10-15 years. Third generation Legacy parts are already being discarded. One of my former tech's works at the dealer parts department and he priced out an FA engine rebuild after a piston skirt failure and was over $9k in just parts. How long before that's WAY more than the value of the car? And when the electrical systems go haywire and you can't get any replacement parts or repairs..... the 4th gen Legacy HVAC panels for example. Anything that has CANBUS errors - it's basically a lost cause because no one will spend the diagnostic money to fix them and they can't pass inspections with a CEL. 

I had to let go of virtually all my old Subaru's as they aren't viable daily drivers anymore. Can't get any parts for them. I decided to go back to the Chevy Small Block because they have a WEALTH of available parts and Subaru has abandoned their early philosophy of simple and reliable and over-built to last. At least the SBC, designed in the 50's, was built to last and be repaired. And now my old Chevy's are well supported in the reproduction market - I can literally rebuild them out of a catalog. Not only can I get every part - I can get it in steel, stainless steel, or billet aluminium, and 15 different colors. The arduous search for non-existent parts is tiresome and I have a real life to live that doesn't involve that nonsense. And to top it off - my cars are appreciating in value while I drive them! Try that with a Subaru!

GD