Hi,

I am continuing on a problem I am having with my car that in combination with the rear defroster not working is really a problem in the winter.

Some time in the summer my blower fan for the AC started working intermittently, generally when the car heats up and I shut it off and turn on again the fan stops working and it was a hell summer with no AC. It would eventually kick on and work until the next shutdown. So I learned not to turn off the car for short breaks if I can leave it running. I consulted with a used parts seller and he said it is probably the resistor\control unit that is mounted to the fan so I got that and the fan just in case.
Then fall and winter came and I noticed I am not getting any hot air in the cabin, it is like AC is running, totally cold. If I set the fan to low speed I could feel some hot air, usually only on passenger side and a bit of googling lead me to the valve unit next to the blower fan that is splitting the coolant to the 2 zones. I got that also used and went on an adventure of replacing the parts with a mechanic buddy in his shop.

I replaced the resistor for the new one and swapped the valve. No luck Since some coolant was lost and refiled we thought it had some trapped air in the system. After a lot of time idling, revving and driving there was no evidence of any air in the system.
The fan was working good but after a day it went back to not working when hot. So I got nothing

I cranked the seat heating to max and got used that it's cold in the car while in every drive I tried to play with the climate control to find some trick to get the heat.

What was funny is that if I would floor the car for 10s I would instantly get heat for a short time And in a long drive it would get heat(after an hour or two) eventually. I was going for a vacation on NY and took the car for 500km drive through the mountains. It heated up the cabin half way through and car had no issues overheating or anything, with some hard driving in the revs on the uphill's.
2 days ago I left the coolant tank cap off for the night, but the next morning I was in a rush and forgot to put it back, so I made 20km throught the city with no cap on the coolant tank and lucky me no overheating or coolant spills.

I am thinking I have some clog maybe in the heater core or it's loop. But until I get full heat it still comes from one side mainly. Also, maybe a new valve unit would fix it, maybe the used one was faulty. But I don't want to spend all the money for one to find out it was no issue. So a cleanup of the one on the car might do it.

As for the fan I think I would change it for the used one I got and see how it goes.



Now....a different view on the problem. My starter got really slow on crank up to the point I was afraid if it wouldn't start in temperature is below zero. I got it rebuilt and now it cranks like crazy. But this pointed out a problem I had even before the rebuild but thought it is a starter issue. When I hit the key it would like hit a wall and stop cranking and then continue. Like it pulls too much power and confuses everything and then realizes it has enough power and cranks. Now that it is rebuilt it seems that this problem is even worse. The car would get all crazy, throw errors and once got to limp mode even after a start like that. This happens on half of the starts I would say. My suspect is the battery control module in the trunk on the ground cable and it is faulty and not sending correct current. It has quiescent current stages DTCs which I didn't find much about anywhere.

So I am thinking that maybe my fan not working is caused by this mess of starting procedure. I will get a different battery control module and see.



Sorry for the long post and thanks to anyone willing to read, please suggest if you have any ideas. I have read the forum up and down and did not find one with same factors as mine.

 

Low heat can also come from a thermostat that is stuck open.

 

It could also be the stuck solenoids in the heater valve (P/N 4F1-959-617-B) in the plenum.

 

Thermostat was replaced last year, the car heats up quickly as it did after it was changed. Thanks for the tip
Yeah, I replaced it for a used unit but it did not help, thought of cleaning it before spending money on a different used one or a new one. Just confused me how full throttle pulls push the heat through. I realize that the water pump is flowing a lot more and if it forces the some valve open how it doesn't stay open

 

Perhaps one of the many air-control doors is misbehaving and dumping your heat elsewhere?

 

I did a test with the VCDS, they all seem to work. No DTCs and I could hear every motor moving

 

Either the used valve assembly had same issue as original (if this is the issue) or the heater core is getting plugged up. Have you tried pressure flushing the heater core?

 

Do you know a good guide on how to do that? I never did it

 

I use a couple long hose extensions off the heater core, fill with hot water and hit it with compressed air, repeatedly and in both directions until crud stops coming out.