I've been trying to diagnose the reason why I get no or very little heat in my B5 at idle when the engine is at operating temp, but when increasing the revs the heat is fine.

My thermostat seems to be working, because the needle in the guage goes up to the middle point and stays there as it should as the engine warms up to operating temp. I reverse-flushed my heater core and burped my cooling system this fall. Btw, the heater core was replaced three years ago and "should" be fine.

So last night, I started Brunnhilde up in prep to heading off to the gym for my usual workout. She was running for only about 30 seconds and I was outside standing by the front of the car talking to my wife. Then I noticed that the cooling fan started up. So I grabbed a flashlight and confirmed that it was running.

Now, granted, we are in the middle of a heat wave, and it was about 35 degrees F last night while this happened. But the engine was cold and had only been running for about 30 secs. I checked the temp guage and she was still way over to the left, which is correct. Brunnhilde's engine normally takes a good 5 minutes of driving before it gets up to operating temp.

Upon consultation with the Bentley guide, I read that the fan is supposed to start when the coolant is at 92 C for stage I(fan speed I presume) and 99 C for stage 2.

Could this be the root cause of my heating issue? Perhaps the fan is coming on way too early, or maybe it's going into stage 2 before 99 C?

Does this point to the coolant fan temp sensor as the culprit?

I was going to check the temp of the coolant, but offhand I don't remember the secret handshake with the stereo that will display this. Could someone please refresh my memory on how to check that?

As always, many thanks for any assistance you guys can give.

 

If you are talking about the clutch fan, it might be locked and spinning all of the time.

 

is your coolant topped off?

 

You can check your coolant temp,using a vag-com cable,then starting the vag-com software,go to measuring blocks and choose the correct module for the coolant temp,i did it before i saw real time the temp of the coolant and other goodies.

 

I'm not familiar with the term "clutch fan", the Bentley guide calls it the coolant fan. Anyway, it's the fan that's inside the cover, not the fan that's connected to the serpentine belt. This is the left side fan of the two in front as you're looking at it from the front looking toward the bulkhead.

What's the test to check whether it's locked, and how does one unlock it if it is locked?

Thanks for helping me, I really appreciate it.

 

Yes it is. Are you inferring that there's some kind of sensor in the overfill tank that triggers the fan to turn on if the coolant is low?

 

Aw yes, I do not have VAG-COM yet. It's on my list of things to purchase soon. I almost ordered the whole HEX-USB+CAN package yesterday, but then my wife's Hyundai decided it needed a new exhaust pipe yesterday, so there went those funds.

Btw, the reason I'm going to go with the HEX-USB+CAN is so when I finally do put Brunnhilde out to pasture, I can use that setup with my new B7 or B8 in a year or so.

 

I see now..i assumed everyone had a vag-com on here,was the very first thing i purchased after joing AF,too many people are advising you to buy one so they can better help you.

They are dirt cheap on ebay for like anywhere from $9.00 to $15.00 from china,from $15.00 to 50.00 in the USA

 

That fan is only the cars last ditch cooling effort.
That fan is used by tour HVAC system. Set your temp to lo, and the fan will come on

The no heat is an air bubble in your heater core. If you would search, you would literally see about 210 useful threads, as well as how to fix it, because time and time again, people ask this.

 

I think I made it clear in my original post that I have already flushed the heater core and burped the cooling system. And since I noticed the fan coming on right away, I thought I'd ask about it since I didn't know if that was normal or not.

Sorry that my post annoyed you, but I did search and I use the search function all the time here.