Heater blows hot when idle and without filter

[Kupa565]

I have the weirdest thing I have ever seen.
My E46 blows hot air pretty well when idle and cabin filter is removed.
If there is cabin filter installed, it blows cold,however, hot air turns cold when I move.

It would be easier to say, my heater temperature is like dependent on IAT :/
I have no idea what's wrong with it.
If I stay, it takes a few minutes to get warm and if I move, it takes 30 seconds and starts getting cold.

I have replaced Heater Control Valve, I bled cooling system several times but no luck :/

Have you ever seen that crazy behavior of the heater?


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[dworthy]

So I would pull codes from the HVAC module to see what's not happy.

Second you can be looking at a bad water pump on top of things, but the temp won't change as the needle is buffered.

[Kupa565]

So I would pull codes from the HVAC module to see what's not happy.

Second you can be looking at a bad water pump on top of things, but the temp won't change as the needle is buffered.

It has error about Water Valve.
It says short circuit against U-Batt.
I have changed Water Valve btw.

If water pump is broken, how can car keep ideal temps for all time?
Temperature of coolant is absolutely stable and between normal range


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[dworthy]

If you purchased a cheap knock-off, there's a good chance it bad too. I think VDO was the provider to BMW for that part.

Your temp gauge is buffered for something like 30 degrees C. so keep that in mind here. If you didn't know, ever since the E-36, BMW has "buffered" the temp gauge as people would come in when it started to get to the 3/4 line and complain that it was overheating. Shoot in the E-9x they took it out completely.

[Kupa565]

If you purchased a cheap knock-off, there's a good chance it bad too. I think VDO was the provider to BMW for that part.

Your temp gauge is buffered for something like 30 degrees C. so keep that in mind here. If you didn't know, ever since the E-36, BMW has "buffered" the temp gauge as people would come in when it started to get to the 3/4 line and complain that it was overheating. Shoot in the E-9x they took it out completely.

I didn't mean temp gauge, I meant OBD coolant temperature reading in real time.

How can I test Water Valve?


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[dworthy]

Two way to test the water valve, one is to check for power at the plug/connector into the heater valve. Should be battery voltage with the heat set to high. Also a valve will fail in the open position, but you are not getting full heat.

Second way is to take a heat gun and check both hoses for temperature. The ones I am talking about goes to the heater core, the return should ride along the frame rail, and the hot side is above it at the heater valve. If you rev it up and both hoses become close to the same, then I would say you need to flush the heater core. If the temp drops, then the valve is the problem, and unplug it to see if it gets hotter.