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No heat, but only while driving

cb1111

Newbie
Location
Virginia, USA
Did you figure it out?
I doubt that the poster will answer

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VW'15GTI

New member
Location
Canada
Car(s)
VW GTI '15
I guess I'll need to find out the answer somewhere else by myself. Was hoping maybe he'd get a notification so he would come back to answer...
 

Corprin

Autocross Champion
Location
Magrathea
Car(s)
A car
Some guys do that?

yep. I’ve been known to go scorched earth on forums.
I guess I'll need to find out the answer somewhere else by myself. Was hoping maybe he'd get a notification so he would come back to answer...

don’t want to be a dick, but if you are having similar issues… why not try the ideas presented in this thread, rather than shopping for the answer?

It’s likely a failed thermostat.
 

VW'15GTI

New member
Location
Canada
Car(s)
VW GTI '15
Because the solutions range from getting a new Heater Matrice/Exchange, changing the thermostat, blend door and heater control valve. Just wanted to make sure I apply the good fix. Especially after this comment :
I'm guessing the thermostat is stuck partially open. When idling, there is no cold air blowing over the radiator cooling the coolant down to low temps, but when you drive and the thermostat is stuck open, the air is cooling everything down enough to make the heater air cold. Also the engine coolant temp displayed on the cluster gauge is more of an estimate.
There's definitely no drop in temperature while driving at high speeds at -20C in regards to the coolant temperature.
 

Corprin

Autocross Champion
Location
Magrathea
Car(s)
A car
Because the solutions range from getting a new Heater Matrice/Exchange, changing the thermostat, blend door and heater control valve. Just wanted to make sure I apply the good fix. Especially after this comment :

There's definitely no drop in temperature while driving at high speeds at -20C in regards to the coolant temperature.
what is coolant temperature at idle, are you having the same warm at stand still cold at speed situation? How long does it take to get your coolant to said temp from cold start?
 

nunex

Passed Driver's Ed
Location
Portugal
VW 15GTI,

I got a similar problem that kept me busy for quite some time until I found the culprit.
The problem was that it took really a lot of time to start having warm/hot ir on the vents on cold nights (below 10ºC). Sometimes it took almost 12 minutes for air warm up. Despite, real time monitoring of coolant temperature shown it was reaching nominal values pretty fast. If temperatures were milder (12ºC or above) I was getting hot air the cabin pretty fast. I also no problem if there was some residual heat on the engine compartment (like the car sitting for 2 or 3 hours)
After lots of troubleshooting with the dealer (they just could not figure it out), I found it myself: N82 valve, that controls the flow of hot water from the engine to the heather core got somehow stuck when temps were lower, so it was not opening!
After replacement , I got warm air in 2 min, no matter the outside temperature.

I hope it helps!
N.
 

VW'15GTI

New member
Location
Canada
Car(s)
VW GTI '15
what is coolant temperature at idle, are you having the same warm at stand still cold at speed situation? How long does it take to get your coolant to said temp from cold start?
Idle it drops to around 87-90C. Speed is around 90-100 depending on how hard I press it. I don't know how long it takes. I'd say it's pretty fast (under 5 min). Will check next time. But even with coolan at 90C, I've had driver temps of 22C while passenger was 9C (obd11 live data). Here's a quick video of a 15 min drive.

VW 15GTI,

I got a similar problem that kept me busy for quite some time until I found the culprit.
The problem was that it took really a lot of time to start having warm/hot ir on the vents on cold nights (below 10ºC). Sometimes it took almost 12 minutes for air warm up. Despite, real time monitoring of coolant temperature shown it was reaching nominal values pretty fast. If temperatures were milder (12ºC or above) I was getting hot air the cabin pretty fast. I also no problem if there was some residual heat on the engine compartment (like the car sitting for 2 or 3 hours)
After lots of troubleshooting with the dealer (they just could not figure it out), I found it myself: N82 valve, that controls the flow of hot water from the engine to the heather core got somehow stuck when temps were lower, so it was not opening!
After replacement , I got warm air in 2 min, no matter the outside temperature.

I hope it helps!
N.
I've seen that this solved this particular issue (warm engine, no heat) for most of the people. While I do seem to have the same issue, I'd say there's also the fact that driver (left side) is hotter then passenger by like 20C. So it might be something else (low coolant, clogged heater, thermometer). I'm trying to find what exactly is the issue before spending money. Btw, how much cost the N82 valve?
 

rye0pa

Go Kart Newbie
Location
NJ
I have had this happen on a few cars over the years. I would be it is a bad thermostat. 95% sure
 

VW'15GTI

New member
Location
Canada
Car(s)
VW GTI '15
I have had this happen on a few cars over the years. I would be it is a bad thermostat. 95% sure
Anything in particular I could do to diagnose it? From my understanding, while driving, the coolant temperature should go down if the thermostat would be broken?
 

kevinkar

Go Kart Champion
Location
United States
I've never replaced a thermostat on a Golf so don't know what the idiosyncrasies are but on every other car I've had it's a $10 item, a couple screws and 10 minutes. If the car still has issues, at least you'd have a new thermostat and a spare in case that one goes out. Seems like a quick check to me.
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
I've never replaced a thermostat on a Golf so don't know what the idiosyncrasies are but on every other car I've had it's a $10 item, a couple screws and 10 minutes. If the car still has issues, at least you'd have a new thermostat and a spare in case that one goes out. Seems like a quick check to me.
I can't cite the procedure but from what I've read it's very time consuming.
 

VW'15GTI

New member
Location
Canada
Car(s)
VW GTI '15
It is time consuming and costs +/- 500$. Don't want to be spending money on something that's probably not broken. Plus, with all the issues revolving around the water pump / thermostat I'm gonna abide by the proverb don't try and fix what's not broken. Coolant temps, as seen in the video hover from +/- 85 to 105. I'm not sure it should variate that much but since I never logged it, I don't know.
 
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