2015 Passat - poor heat

ilyago

Veteran Member
Joined
Mar 14, 1999
Location
Chatham, NJ, USA
TDI
2015 Jetta S DSG
I am starting a new thread since my problem seems different from the heater core issues.

2015 Passat SE Manual 57K miles

History:

Jan 2016 (11K miles) - I complained to the dealer that my heat is not working as well as it should. Dealer wrote it off that "diesels take longer to warm up". Instead of bringing up the obvious faults in that argument, I decided to get the issue documented and wait until the problem got worse. This was my first winter with this car, so I had no prior experience with its heater.

Nov 2017 (57K miles) - no heat at all. Dealer diagnoses a clogged heater core. Replaces heater core, changes coolant. No TSB or extended warranty for 2015 models. VW corporate refuses to give any assistance. Dealer service manager negotiates with VW, my bill comes to $255 plus tax.

I pick up the car to discover that I am back to low heat, similar to 2016 levels.

Since now the heat issue is in the spotlight, I pursued the matter further. Take the car back next day. Service advisor says that the temperature measured at the vent is "within acceptable" range. I disagree, come back the next day to measure.

I drive the Passat about 15 miles on the highway, water temp gauge is pointing straight up (190?) and oil temp is above 200.

Compared to my 2015 Jetta TDI. I get 160 F with the Jetta, 100 F with the Passat. Service manager gets it to go a little higher by gently revving the engine and observes it changing between 100 - 120 (?) F "due to thermostat opening and closing".

According to the SM, there's no written spec as to what the vent temperature should be - I disagree, I am sure VW has a spec. He tries to explain that the diesel engine computer/thermostat will favor keeping the engine cooler over providing better heat for the passengers, so I am to expect lower heat in a TDI. I question why my Jetta's heat is 60 degrees warmer. He agrees to have a factory rep look at the car next week.

Questions for the forum:

- has anyone else experienced this issue? were you able to resolve the problem?

- if you have a 2015 Passat and you are happy with your heat, please let me know as well

- does anyone know if there's a heating spec for the 2015 Passat TDI SE (manual controls) and what is the temperature range for the spec?

- any ideas on what could be causing this?
 

roni024

Veteran Member
Joined
Mar 31, 2007
Location
Syracuse, NY
TDI
2015 Passat TDI SEL DSG
It sounds like it could be the blend door is not properly moving. There are searchable threads here that can explain it for you.
 

Jedadiah

Veteran Member
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Sep 17, 2010
Location
Central Kentucky
TDI
Former: '15 Passat TDI SE 6M, '15 Golf S 6M and '10 JSW
Both of our 2015s heat up substantially quicker than the 2010 I had. The EA288 was designed to heat more quickly than the earlier models, so I’m sure you have an issue. Isn’t nice when the dealer just brushes your issue off as a diesel thing?
 

ilyago

Veteran Member
Joined
Mar 14, 1999
Location
Chatham, NJ, USA
TDI
2015 Jetta S DSG
It sounds like it could be the blend door is not properly moving. There are searchable threads here that can explain it for you.
I found many threads on the blend door, but none are for an NMS TDI...

Would the issue/solution be similar to the older cars?
 

ilyago

Veteran Member
Joined
Mar 14, 1999
Location
Chatham, NJ, USA
TDI
2015 Jetta S DSG
Played with the controls as I was driving. There was another related issue that I complained about in 2016 - the blower was barely blowing, even when set on 6. Looks like if I leave the blower on 6 - when I turn the temperature to cold, the blower speed picks up significantly; when I turn it back to hot, it slows down.
I usually keep the blower at 3 or less, so I never noticed it before.
This also is affecting my defrost function. Turning on A/C or RECIRC function does not affect the blower speed.
It seems like something is blocking the air flow when the temp is set on hot.
 

Funguy

Veteran Member
Joined
Jan 18, 2005
Location
Front Range of Colorado
TDI
2015 Golf Sportwagen dsg and 2015 Passat 6 M/T
Hope I am not being obvious but when you turn to cold the A/C automatically switches to recirculate which always sounds louder. Could that be why the fan sounds more powerful in cold than hot?
EDIT: I see you have already played with the recirculate function sorry.
 

ilyago

Veteran Member
Joined
Mar 14, 1999
Location
Chatham, NJ, USA
TDI
2015 Jetta S DSG
Its not just the sounds, I actually can feel the air blowing hard when the temp is on cold, while it is barely blowing when I move the temp to hot.
 

Tom in PT

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Joined
Jun 7, 2017
Location
Twilight Zone, WA State
TDI
2005 Passat sedan - SOLD; 2013 Passat DSG; both purchased new
This may not completely solve your issues, but check to see that the door to the cabin filter housing above the passenger footwell is closed. Otherwise cold air will pour into the cabin as you drive down the road.
 

JKC_NC

Veteran Member
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Location
Raleigh
TDI
'15 Passat TDI DSG | '15 Passat TDI SE Manual (sold 7/2018) | '10 Jetta Wagon TDI manual (sold 4/2015)
This may not completely solve your issues, but check to see that the door to the cabin filter housing above the passenger footwell is closed. Otherwise cold air will pour into the cabin as you drive down the road.
Mine started smelling dank. When I went to change the cabin filter, about a cup of leaf debris fell out. I could imagine the cabin filter being full and blocking flow. Worth checking.
 

ilyago

Veteran Member
Joined
Mar 14, 1999
Location
Chatham, NJ, USA
TDI
2015 Jetta S DSG
I change the cabin filter every spring, right after the pollen season around June. It never has too much stuff, but I buy a filter kit from idparts which includes the cabin filter, so I change it every year. I would imagine if the filter was clogged, both hot and cold blow rate would be affected the same way.
 

740GLE

Top Post Dawg
Joined
Aug 19, 2009
Location
NH
TDI
2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
It may not be the filter is clogged but the filter access pannel may not be fully seater when you changed it out last time
 

ilyago

Veteran Member
Joined
Mar 14, 1999
Location
Chatham, NJ, USA
TDI
2015 Jetta S DSG
Update:

The factory rep visited the dealer and advised to perform multiple coolant flushes. After several flushes, the new heater core got clogged. They ordered and installed a new core and flushed some more.

So after several days, the heat is now working, they claimed getting readings of 160-180 degrees at the vents. And the blower is blowing better as well, so I suspect the flap is temperature sensitive - does anyone know?

No charge for all the remainder of the work. Just the initial $ 255 + tx "customer participation" for the initial heater core replacement.

I still haven't heard of anyone else having the same issue with a 2015 Passat.
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
It's disappointing to hear that the 2015s are afflicted with the same heater core and coolant problems as the 2012-2014s. I'm glad VW got your heat working again, but I suspect you haven't seen the last of this problem. :(
 

740GLE

Top Post Dawg
Joined
Aug 19, 2009
Location
NH
TDI
2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
Use and abuse of the coolant and its breaking down.

I fear this will be faced in the EA888 Gen3 1.8 TSI, coolant loops through the head is great for getting up to temp quick but I fear it can't dissipate the heat once up to NOT.
 

BarryMunson

Well-known member
Joined
Aug 13, 2004
Location
Cleveland Ohio, U.S. of A.
TDI
2014 Passat tdi SEL
I am experiencing the same thing with my 2014 TDI. I did about six vacuum extractions of coolant (some were just water). I changed the heater core and filled the system again. The core I took out is not blocked in my opinion because I can blow air through it. PLenty of water came out of the old core when I took it out.
When I run the engine up to temperature the core inlet and outlet are not getting hot and there is no cabin heat.

I was wondering if the flow is blocked at the EGR.

Or could I not have coolant in my new core yet.
 

740GLE

Top Post Dawg
Joined
Aug 19, 2009
Location
NH
TDI
2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
I am experiencing the same thing with my 2014 TDI. I did about six vacuum extractions of coolant (some were just water). I changed the heater core and filled the system again. The core I took out is not blocked in my opinion because I can blow air through it. PLenty of water came out of the old core when I took it out.
When I run the engine up to temperature the core inlet and outlet are not getting hot and there is no cabin heat.

I was wondering if the flow is blocked at the EGR.

Or could I not have coolant in my new core yet.

For you're knowledge, when the heater core clogs, it clogs the fins first and shuts them down but will never fully clog blocking flow as the coolant loop still needs to flow.

Basically as the core clogs, it creates it's own bypass with the only side affect being lack of cabin heat.

One of the easiest ways to check if its clogged before you remove it, get car up to NOT driving for 10-20 minutes. place fans on 1 heat at max, take a non contact thermal gun and measure in in and out of the core plumbing, if they are the same there is no delta of heat being extracted from the core to the cabin. If there is a slight delta then its slightly clogged.

I'm not sure what a clean perfect core will have for a delta, but I'd guess 190f in at least 160 out shouldn't be that out of this world.
 

BarryMunson

Well-known member
Joined
Aug 13, 2004
Location
Cleveland Ohio, U.S. of A.
TDI
2014 Passat tdi SEL
THANKS 740GL,

Since I have already replaced the heater core, these are test results of my new core after about 6 engine coolant flushes using the vacuum method. The new core was put in place after these 6 flushes.

I followed your fixed setting parameters on the controls of:

1. Max T
2. fan speed 1
3. I also added one more parameter of Vent position only (no foot well heat) as this screwed the readings).

As for the non-contact thermal gun, I placed black tiger tape targets on inlet and outlet for pointing thermal gun on the core's inlet and outlet aluminum tubes because all cheap non-contact thermal guns measure "emissivity" which leads to errors in readings when pointed at shiny surfaces of differing reflectiveness.

Test results:

Preface:
I started readings based on engine temperature gauge readings. I know that the electric heater turns off very close to the 190 F engine temperature (based on hearing the relay turn the grid off) so I took reading just before the heater grid turned off and after it turned off.

At 185F
1. Left vent was 150F
2. core inlet: 155F
3. core outlet: 85F

At 190F (about 1 minute after the electric grid heat turned off)
1. left vent was 126F
2. core inlet: 167F
3. core outlet: 100F

It is 20F out today and I plan of reporting heating comfort results after a test drive with controls set as above.

Back from test drive:

1. Outside temperature rose to 27F for the test drive. I ran for 15 minutes at 60 to 65 mph and the cabin left vent rose up to 165F.
2. after returning in to the garage, the core readings were:
inlet: 193F
outlet: 133F


Conclusions:

If you change a heater core, it needs to be baby burped after changing the engine coolant by running at higher rpms or at road speeds in order to clear the air out of it. I know it did not happen when I ran at idle in my garage because I could not get good differential core inlet/outlet delta T readings.
 
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740GLE

Top Post Dawg
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NH
TDI
2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
So looking for a delta of around 50F or so on a new core. I'd be curious to know how that tracks after 20-40K or so, that delta is going to drop.

Also the only really way to know coolant temp is use a scanner.

The needle will show dead nuts 190 for anything between ~160F and 230F. I think you've verified that as you measured 167F even though the car was showing 190.
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
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Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
The delta may actually increase as the core clogs because the core has more time to extract heat from the limited water flowing through it (reduced flow exposes that water to the heat exchanger for a longer period of time, resulting in more heat extraction from the fluid). This seems counter-intuitive on the surface, but that's how hydronic heating systems work. Too much flow results in a low delta T, too little flow results in a high delta T.

There are, of course, variations on that depending on the condition of the system. An externally clogged heat exchanger (impacted with dirt) can result in a low delta T across the water inlet/outlet.

So I guess the take-away is that this is not a one-size-fits-all situation and the condition of the entire system's condition must be taken into consideration when troubleshooting.

Now - if the system is self-bypassing as it clogs, the delta T will drop as the core's internal passages become restricted. I haven't held one of these heater cores in a couple of years, so I can't confirm that they are self-bypassing. I am pretty sure that they are not, but I could certainly be wrong.
 
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BarryMunson

Well-known member
Joined
Aug 13, 2004
Location
Cleveland Ohio, U.S. of A.
TDI
2014 Passat tdi SEL
So looking for a delta of around 50F or so on a new core. I'd be curious to know how that tracks after 20-40K or so, that delta is going to drop.

Also the only really way to know coolant temp is use a scanner.

The needle will show dead nuts 190 for anything between ~160F and 230F. I think you've verified that as you measured 167F even though the car was showing 190.
I forgot that my Actron scanner can monitor the engine data and could have used that had I known of the wide range of temperatures that produce a 190 F reading on the gauge.

I now have all of the panels in place so I cannot read the true engine temperature after 20-40K miles of road time.

My data was, however for the 190 F readings, taken after I heard the relay drop out the heater grid and also heard the engine RPM adjust.
Maybe that is a positive indication that the engine was up to 190F?

As a side note, I remember that when I did the engine coolant evacuations that a dark colored small .5 to 1 mm sized grain was pulled out during the first 4 evacuations into the vacuum's housing. Later I took the old core and poured tap water into the inlet and outlet. Each time that I filled it, I turned the inlet and out upside down and brown semi-transparent thin flakes about 3 mm poured out into the stoppered sink basin. NO granular particles came out of the core.
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
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Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
The dash gauge will display 190°F (or 200°F in a Touareg) anytime the actual coolant temperature is between 166°F and 225°F. This has been VW's standard gauge buffer for the better part of two decades (since the introduction of the Mk4 in 1999, possibly even earlier).

The command to run the PTC cabin heater (1,000 watts) is calculated based on engine temperature and HVAC heating demand. If the driver demands less heat, it will shut off the PTC heater sooner. If the driver demands more heat, it will run the PTC heater longer and at higher coolant temperatures. There is no consistent cut in/out point for the PTC heater that you can use as a reference point.
 

740GLE

Top Post Dawg
Joined
Aug 19, 2009
Location
NH
TDI
2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
The delta may actually increase as the core clogs because the core has more time to extract heat from the limited water flowing through it (reduced flow exposes that water to the heat exchanger for a longer period of time, resulting in more heat extraction from the fluid). This seems counter-intuitive on the surface, but that's how hydronic heating systems work. Too much flow results in a low delta T, too little flow results in a high delta T.

There are, of course, variations on that depending on the condition of the system. An externally clogged heat exchanger (impacted with dirt) can result in a low delta T across the water inlet/outlet.

So I guess the take-away is that this is not a one-size-fits-all situation and the condition of the entire system's condition must be taken into consideration when troubleshooting.

Now - if the system is self-bypassing as it clogs, the delta T will drop as the core's internal passages become restricted. I haven't held one of these heater cores in a couple of years, so I can't confirm that they are self-bypassing. I am pretty sure that they are not, but I could certainly be wrong.

Agreed with your theory with hydronics heating and a series blockage in base board radiators, and flow is reduced to a trickle.

Except the if you look at the heater core, its U shaped in nature with cross connects (parallel) in both legs of the U. as those cross connects clogs, the flow just bypasses them up until no flow is through the any of the cross connects. If it was series, as the unit clogs you are now hindering flow of the entire coolant loop and increases chances of over heating.

It kinda makes sense they designed a fail safe into the core. Would you rather have poor heat or over heating and possible head gasket failure for an issue with a heater core.
 

compu_85

Gadget Guy
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Sep 29, 2003
Location
La Conner, WA
TDI
... None :S
Well, remember some people's cars throw codes for the EGR Cooler efficiency... the EGR cooler is directly upstream of the heater core. When the core plugged, flow was restricted on the EGR cooler.

-J
 

740GLE

Top Post Dawg
Joined
Aug 19, 2009
Location
NH
TDI
2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
Right and what was the temps of the inlet and outlet of the core? surely there isn't a delta of a new core. I'd wager the delta would be minimal and it's now at the point of restricting flow.
 

dustinp

Member
Joined
Sep 9, 2012
Location
Mora, MN
TDI
previously 05.5 Jetta TDI 5sp manual, 2015 Passat SE TDI 6sp manual
I recently experienced the "no heat, only cold air from the vents" phenomena, so based on other posts decided to replace the heater core. After replacing it, I found I had heat, but when we had some unseasonably warm weather a few days later I turned on the AC and could not get any cold, and only full on heat! I removed the under dash panel, and ventilation distribution tube to see if I had reinstalled something wrong after replacing the core, but found nothing amiss. What I did find was that with the ignition and fan on, when I tapped on the blend door motor with the handle of my screwdriver, the blend door arm moved, and the vents were now blowing cold air. When I turned the temperature control knob back and forth from hot to cold, the arm sometimes moved and sometimes didn't unless I tapped the motor housing again. I ordered a new blend door actuator motor, and replaced the fickle one, and everything seems to be working fine now....but it makes me wonder if the blend door actuator wasn't the maybe only problem from the beginning, and a heater core maybe wasn't needed. Neither job is fun, but only doing one would certainly be preferable to doing both.

So if you are experiencing a situation where the air temp doesn't seem to react to changes you make in the temperature control knob, where you only seem to have cold, or hot, or somewhere in between, but no corresponding changes with the knob, you can check to see if the arm that goes from the blend door actuator motor to the blend door flap is moving or not. You can do this without removing any panels, by looking through the opening below the steering column, and up and in toward the center behind the radio. You'll see the white arm, and if you turn the temperature control knob with the ignition on, and the fan blowing you should see the arm going forward and back as you turn the temp adjustment from hot to cold.

Here is a pic of that actuator arm when looking through that area below the steering column. You can see it in the center of the pic.
https://forums.tdiclub.com/index.php?media/passat-blend-door-actuator-arm-jpg.150669/
 
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