Randolph

For many that have been on the forum for years you'll recall that I replaced my heater core and ever since the heat hasn't been as strong as it should.

It works but not nearly as hot as before. I keep it fairly cool in the car but it's nice to have the capability of full hot heat when your warming up the car.

Airflow is perfect. This is ONLY a temperature issue.

I've gone through everything and nothing seems to be causing a problem.
Thermostat is fine. Engine gets hot
Temp control cable is good not binding
CC head is fine
Programmer is fine
Both hoses going to and from the heater core are hot
I even disconnected the the temp cable from the box and manually moved it to full hot and still it's not correct.

The only logical thing left is for some bizarre reason I'm thinking that one of the temp doors is not lined up properly.

I got the box out last night and today I'll take it apart and have a look. I'm hoping I find the problem in there.

On a side note, I did such a good job replacing this thing the first time I really hated to have to touch it again. It looked as if it was never touched down to the wire ties. Oh well. This time when I reseal it instead of using the putty type stuff (same stuff Audi uses to seal the rear taillamp) I'm going to use a bead of 3M windshild seal. I think this will work as well or better than the putty.

Any thoughts on this problem?

R

Kneale Brownson

I noted elsewhere you want to seal the box, not glue it back in, so a windshield adhesive wouldn't be your best approach.

RB-200 20v

When I replaced my core I was worried about the flap position thing, took pictures of positions before splitting the halves and after splitting the halves. After getting it apart and looking at it I came to the conclusion, correct I believe, that if the drive mechanism is not moved after taking apart the flaps will return to the correct position. Since it is keyed, if not moved, the flaps will go back to the position they were when taken apart [and whatever setting the CC was before removal remains the same throughout the R&R process].
So, did you move the drive after taking things apart? If so, I really don't know how one would get back to the pier, so to speak. Unless you were to acquire one of the flap jigs shown in Bentley. If you didn't move it, maybe you damaged one or more of the plastic levers when you put the box back in.

Good luck

Firechicken

Hey mate, you most likely checked this if you have one, but just in case, my 5k's anyways all have near the firewall and tranny bellhousing have on one of the heater core lines a vacccume operated coolant flow valve.

On mine when the valve failed it was giving similar trouble like yours, where when grabbing the heater core lines they were getting hot, hwever I wasn't getting enough heat from the vents. After checking vaccume servo motors, and making sure if any of the flexable vent couplings under the dash had come loose, I noted that after testing the heater core coolant valve was only opening about half way.

What happend was then when one touched the hoses you'd have hot hoses, however the valve only opening half way was not allowing enough VOLUME of hot coolant to flow through the core, thus it's output wasn't suffucuant. Chaning the cheap valve out wih a new one resulted on nice hot air again.

This might not be your probblem, but I thought i'd mention it just in case.


Also there are output tests that can be performed on you CC box and motor arm location relative to the signal the CC head is saying it should be at, in numerical value, so the head might be saying 1 for example, then the next test says another value of where the CC unit is actually reporting the motor's position say maby it reports a value of 8, which would indicate it's out of whack. It's fairly easy to get this setup closely enough with a bit of tinkering. I can dig up the procedures if you need them.

Anyways good luck, just offering up some more ideas anyways.

Mike.

Firechicken

Oh sorry sorry, I just realized after reading again you all were talking about the actual flap and gear bits, nd not the flap controllers and CC box.

Cheers.

Randolph

I took the box apart and as I suspected everything inside is perfect. All flaps are moving as they should. On a 5000 the box can only go back together one way. My thinking was that maybe one of the temp flaps was perhaps out of sync. For example it's turning from 1:00 to 4:00 instead of 12:00 to 3:00. Audi has the box designed with the movement of the flaps built into the box. So when I have the box apart I can move the temp lever and see all the flaps moving correctly to their full cold or full hot position. There are two other flaps that control air flow but that has not been a problem so no need to worry about those.

Another thought I had is if my temp flaps were out of whack my A/C also wouldn't be working correctly but it works fine. Nice cold air.

I ran water through the heater core from the supply side (lower connection) and from the return side (upper connection) and there is no restriction. I had even reversed the connections while this was still on the car to see if that made any difference being that there is a ck valve in the heater core but it didn't. (I really don't think it makes a difference how you connect the supply and return as long as hot water flows through it. Said ck valve seems to do nothing in my experiments)


I took the heater control valve off and checked it and it works fine and holds a vacuum. I am wondering if maybe when everthing is hooked up I'm not getting enough flow through it as Firechicken mentioned. Maybe for some reason it's only opening only half way? I'll look into that more once I get everything put back together.


Kneale, I commented on the 3M stuff on the other forum. Please see that and advise. Thanks.

R

Kneale Brownson

The default position of the heater valve is OPEN. It only closes for A/C use.

Which year car is this?