So guys, just an update, I'm frustrated...replaced heater core, have a ac ignitor code-NO other codes??? Flap door opens with hvac control unit, but door stops at around 71 degrees-no blockage, flap motor working fine, cold/hot flap working fine and all vaccum doors working fine??? Recirc button works ,but now, snowflake for AC does not stay on either....it did that before I disassembled it?? AC ignitor code was there also before hand....so now, I have NO AC and NO heat???

Could it be the coolant temp sensor even though I'm NOT getting a code??

OR any other ideas???????

Thanks....

marky

 

Just a quick update and another question....I have heat, but ONLY at around 4000 rpm, blows for awhile and then just quits and goes cold..then comes back when it wants and goes away.....when car is ideling, there is no flow from the heater core hoses...remember, new heater core, flushed system over 10 times, 'burped' it, car does NOT overheat, still no heat....no codes etc... so, when it does blow, temp is at 140 degrees...

My question is, does anyone have a diagram of where the heater core hoses come from? where they attach to?

Thanks.

 

I feel your pain, brother. Mine works better than yours, but I'm still blowing cold air at idle during the winter. Once I get her up to about 2000 rpms the heat is good.

At least we've survived another winter and have all summer to figure it out!

 

Jdahlen24,

I'm gonna figure this out and let you know. Looking at some schematics I found on google, it seems like the return return hose goes back into a cooling hose, but the 'IN' heater core hose, it comes out of something....that's why I'd like a labeled schematic/diagram of the engine/cooling system, so I can get a better idea.....

 

How about a .... it's getting cold again and my heat doesn't work bump

 

I finally gave up and took mine to my Audi mechanic, and he got the heater core flushed properly by using SNO-BOL toilet bowl cleaner and lots of compressed air. Back to lovely Audi heat again.

I never did get it right. I tried the CLR treatment last year, and the SNO-BOL treatment this year, but apparently the secret to success on my car was the use of a lot of compressed air.

 

Finally got around to doing on my 175k 2000 A4.

I went to HD and got 5 feet of 3/4" ID vinyl hose, a drill pump, CLR, and some barbed fittings.

I hooked up the hoses to the inlet and outlet of the heater core and used the garden hose to back flush and flush the heater core. I did this until the water came out clear in both directions. A lot of rusty scale like material came out and took about five flushes.

I then poured in most of a CLR bottle and hooked up the drill pump. It was really messy so I had put down a plastic sheet to protect the metal and plastic engine bits from the CLR. The vinyl hose didn't make the best seal so it would leak a bit.

I ran the drill pump for about 10 minutes alternating direction often and then let the CLR sit in the core for an hour.

After that I flushed the CLR out of the core, filled it up with coolant and hooked up the heater hoses.

I took it for a drive and I now have full heat

We will see how long it lasts.

 

What does it take to replace the core? Is it dash out?

 

I have taken the heater core box out without removing the whole dash in my A4 B5, i'm doing the same job in another one at the moment..
i use a length of hot element wire from a hairdrier & a car battery to cut thru the vent tube that runs from the box front up to the dash side vents, the vents got to be silicon glued back together afterwards.
But, inside the heater core theres a wavy bit of 0last8c that seperates the incomming hot from the outgoing cold, making it flow down thru one side of the heater core & back up thru the other side & out thru the outlet pipe.
If that plastics broken up it can cause the core not to work.
Realistically if somebody was paying me to do this job, i would fit a brand new core.
Im actually doing this work so i can replace the ruined foam on the flaps because the original stuff breaks down & lets the air go thru the holes in the flaps, so that could be the cause of the heater not working correctly.
On my B6 the flap blend motors not working correctly & i think thats because of bad potentialmeters resistors.

I checked that core by filling it up & putting some inkject dye in one hose & letting it sit for a while & see how much of it has 'bled' across into the other hose.
So put s9me 8n the 8nlet pipe, leave it for a while & pour out via the outlet pipe & if theres slight colour & then clear & then dark colour, i guess its OK.
If its darkish, then clear, then darkish again, i i would double check it.

Open thermostat will do the same, but you notice it on the dashboard. One B5 of mine is like that & i 5h8nk somebodys mixed coolants because theres 'snot' in the coolant.
Gotta replace the thermostat housing for the Aluminium one anyway. Its the V6 APT engine.