Is there coolant in the system?
Have you done any other troubleshooting?

 

Coolant is full. Any other suggestions for what might be going on?

 

I've never heard of supplementary electric heat. What's your reference to this?

 

My mistake. I misinterpreted some posts on here when trying to figure out if anyone else had similar issues.

 

I took the system off auto and pushed the temperature dial all the way to the right did I get anything

How much did you get? Hot? Warm? Not cold?

which I assume is the supplementary electric heat

The Forester does not have electric heat

What was the outside temperature when you were using the automatic heat?

 

The auto setting relies on a temperature sensor to function. If you can get heat in normal doses using manual control, my hunch would be a problem at the sensor. But it sounds as if you're having problems even manually controlling the heat. Are both sides of the car equally cold or warm at the vents?

 

Outside temperature when the issue occurred was in the low 60's. The problem started about an hour into a three-hour drive, when I noticed that cool air was coming through the vents no matter how high I turned the heat.

Today, on a much shorter drive of about 30 minutes, it blew a little heat for a time and then stopped blowing completely. Outside air temp was in the low 60's. Both the fan and the vent settings were on auto. I took them off auto and cranked the heat dial way up. It did release some heat, but very weakly. Every time I went back to auto the fans shut back off.

 

I would contact the shop that replaced your TCV.

 

I took it to the dealer last night. After not hearing back from them till late afternoon I finally called. "Oh, it's fine. Heat works." I kept explaining to them that it takes a little time for the heat to stop working and to leave it on auto. They tried it again and called to tell me it's fine.

So I have a car without heat that has 42k miles on it, heading into winter, and a dealer that gave me the equivalent of an emoji shrug.

 

Your next move is to call SOA and escalate.

 

Have the dealer show you that the heat is working after 20 minutes or show them. Why are they claiming heat if there is none? Or go to another dealership? SOA usually defers to the dealership diag so I would go elsewhere.

 

Maybe a stupid answer but. I though system worked based upon inside temperature. So if it is cold outside but the heat/air has brought the inside temp to where it is set it would turn off the system.
Just a thought

 

Ever get this figured out? I'm possibly still buying a 2019 without working heat. I'm leaning towards an interior temp sensor, as even on a fairly warm day, the air coming from the vents was a little on the cool side. We're heading into winter. If I get this thing, I need the heater working.

 

@RedGeminiPA you might send the member a PM - Private message. The member is setup to receive an e-mail notification.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

Hi all,

Just joined and found this thread as I'm experiencing the exact same thing on a 2019 Forester Limited. Curious if it was ever figured out as well - the intermittent heat seems to have no rhyme or reason to it. Will report back if I find anything out from local shops in the meantime.

 

My dealer said they couldn't replicate it and so it has gone unfixed. The solution I have been using is to turn off Auto on the blower settings. That seems to get the heat going again.

 

Are you interested in doing some troubleshooting?

1) If you have the color display over your radio, what is the coolant temperature and oil temperature display reading? Do these values sink when the HVAC Auto setting suddenly fails? I'm trying to establish if this is a TCV issue or an HVAC issue.

2) Does the loss of heat happen on all outlets: Floor / Vents / Defrost? Or just some modes.

3) The amount of heat you get is a two-part equation. The temperature of water that reaches the heater core, and the positions of the AirMix damper that blends cold outside air with air that's routed to the heatercore at the bottom of the HVAC box.

If the problem is that the AC Amplifier is directing too much cold outside air into the mix, try switching to RECIRCULATE and see if that changes the temperature.

To see if the TCV is messing with hot water flow only to the heater core (and working fine for engine temperature regulation and thus NO DTC codes!), try removing or reaching around the panel near the gas pedal to get your hands on the metal tubes leading into the heater core and feel for a change in water temperature.

 

Thanks very much - I’ll try these this weekend and report back. We’re at -20 with the windchill so no better time

 

Just to be sure.... I find engine oil temperature (which is an actual digital readout) can vary a bit with driving, but my coolant gauge which is a relative indicator doesn't change all that much. An OBD readout will give you a more accurate picture of coolant temp.

If you are seeing the dash coolant temp indicator move significantly, then the TVC doesn't seem all that stable. The purpose of this complex unit over a simple thermostat is it's superior coolant thermal management.

EDIT: Just to be clear. Coolant temp can vary. The TVC is suppose to sense thermal load in the heads and block and adjust accordingly. It's job is to manage thermal load of the combustion process, by adjusting coolant flow. But it should be smooth and make sense depending on engine load. Again, OBD monitoring of manifold vacuum, throttle position, calculated load, air temp, etc., would give you an idea of how much coolant should vary.

But if it's swinging wildly, then cabin heat can certainly be impacted.

 

I found the two OBD temperature readouts confusing. One readout corresponds to the bottom of the radiator, the other was somewhere near the TCV if I recall. As the TCV did its thing, the readouts would swing significantly. It’s been awhile. I’ll see if I can dig up one of the graphs I plotted.

 

This attachment is from this morning after a few minutes of driving. I’m guessing the water temp is analogous to the coolant temp in this case? Either way, the far left gauge is what fluctuates. Note I didn’t get up to ~90 for oil temp as I wasn’t in the car long enough. I attach this image only to show the gauges that I’m referring to.

the heat in the cabin can vary while on the highway and cools when at slower speeds or stopped otherwise.

I’ll try to get those readouts today.

 

Translating from metric to jolly old english....

You were a bit colder this morning that my area of NY. It was around 10' F compared to your 2' F when I went out for Sunday morning Bagels. The 5 mile run from my rural home into the village was done mostly at 45-50 mph at around 2200+ RPM (rather than 1200-1300 typical) in my drivetrain's attempt to warm itself up. That sunk my avg MPG!

IIRC, my water temp (technically coolant - an antifreeze/water mix - otherwise you'd have cracked your block last night) reached about the same spot (normal running temp) about mid run, but my oil didn't make it past 140' F (you were around 158' F) when I got to the bakery.

I had some heat by 2 miles, great heat with the fan near high speed on AUTO @ 69' F another mile or so later.

 

Very similar climates! I’m likely a couple hours north of you.

I still can’t make heads or tails of the cause other than reading another thread on air bubbles in coolant. It’s like the system is in Auto (it’s not) and starts to cool the cabin seemingly randomly.

Hope the bagels were good!

 

edited for typos.

Below are a couple plots I created back in 2020 when I was trying to understand the thermal performance of the cooling system. I also looked at torque converter lockup in a different set of plots. I don't think this in any way contributes to solving the OP's problem, but it gives a picture of what's going on "behind the scene".

The first plot is of a 45 minute summer drive with mixed residential and highway. You can see the two coolant temperatures oscillate as the TCV controls.

The second plot is of a wintertime drive at a steady 40 mph on a 20F winter day. The variable here is me turning the cabin heat on and off. The coolant and oil temperature , drops significantly when the heater is turned on.

 

MY 2019 just started having heat issues as well in the last month and half. Zero heat comes out, I can hear gurgling inside the car and the only way to get the heat to work is to shut the car off and restart it, then it works but sometimes changing modes will then start pumping out cold air.

 

@QMaze Sounds like you have the dreaded TCV issue.

Also please update your forum profile with details of your vehicle:https://www.subaruforester.org/thre...org/threads/your-forum-public-profile-how-to-fill-this-out.824165/#post-7699120

 

Thank you, I'll give my dealer a call and see if they have issued any recall since this appears to be a big issue with quite a few owners.

 

Quick update from my situation. Turns out I had low coolant (though no leak) and, once addressed, the heat began working as expected. I’m set to have the TCV warranty work done as well.

 

I'll check my coolant level as well too be sure, thanks.

 

Has anyone tried having the heater core flushed? That's where we're leaning for mine. Under the hood, the line on the driver's side was warm, but the one on the passenger's side stayed cool. My OBD scan is showing the heater core temp as very low, but all other temps seem to be within normal range.

 

@RedGeminiPA How well maintained is the vehicle? Did you you have regular coolant changes through out the life of the vehicle. It is extremely rare to have/need a heater core flushed. If it is plugged then so is your radiator. I've never had the heater core flushed on my 2001 with 242,000 miles.