Good morning y'all,

Last night i finally diagnosed why I had no heat in my car. I took the heater valve out, cleaned it and inspected it. When I put it back in the car, I plugged it in turned on the ignition without starting the engine and the whole thing closed. Nothing was getting through it no matter how turned the temp dials.

I turned the car off, unplugged the valve, and turned the car back on. I HAVE HEAT!! (And a/c).

My questions.

1. What's the point of the heater valve if both ad and heat work if it is stuck open? (Like when it's unplugged)

2. What is now the suspect? A faulty control unit for the valve? Where do I even start!?!?!

 

You said you cleaned the valve. That might just be the culprit. You did nothing else and it started working. If you want to see if it is the control unit then you will have to plug up to the car and read if there are messages. I doubt it is because it started working again with you simply cleaning it...

 

Start by replacing the valve.

 

Cleaning it is only one thing that I did. Unplugging the valve which disengaged the flappers is what actually made the heat work again.

 

FWIW: I went through the same same thought process as you when I had zero heat from my '04 545i. I read about all possible fault scenarios not wanting to replace the heater valve needlessly. In the end, the valve was the issue. After two years of denial, I replaced the valve and the heat is working flawlessly. Also, the HVAC system was constantly confused due to asking for heat and getting none. The default response was full defrost most of the time. New valve fixed it all. Just do it!

 

Perfect response. Exactly what it did before unplugging it. I'll do that!

Thanks!

 

Ok, are you saying unplugging the valve while the car is off actually makes it a second thing that you did. The only thing you did was unplug the valve and cleaned it which can only point to: 1. bad connector or 2. bad valve. It would not point to a bad module because you did nothing to the module.

If I had idle issues and I unplugged my IAC, cleaned it, plugged it back up then turned the car on and the issue was resolved i would not think that it could my ecu that could of be the problem. I would say that my IAC was dirty or is bad. Probably a bad analogy but you get the drift. Me unplugging it is just something I had to do to get to it. Was this something you did with the car on. Maybe i'm not getting the concept of this flap. Does it open and close without power on its own

 

I unplugged it, cleaned it, plugged it back in. Turned the car on, no heat, observed no flow through valve still. Turned car off, unplugged valve, turned car back on. Tadaa, heat.

 

Previous 5 series needed 12 VDC on the heater valve to keep it closed. The IHKA controller would remove power from the valve when it called for heat. Unplugging the valve makes it go full open. You've got heat, but it's not controllable. Since your valve opens when power is removed....because you get heat, I think your valve is good. The problem is the IHKA isn't de-energizing the valve.

 

I do get cool air when I turn it to the blue. So I do have some control just it's not ice cold. I would prefer to have this fixed for good so what might the next step be?