Climate Control drifts colder - The Unofficial BMW M5 Messageboard (m5board.com)

erkq · 10th December 2005, 01:18

I did a search about this and didn't find anything so...

My climate control drifts colder as I drive. I bump up the setting a few degrees at a time to maintain a comfortable temp. At the end of about 45 minutes I'm at 89 degrees (F) and that usually does it. Sometimes I have to go that last step to 90. Then I get a LOT of hot air. Go back to 89 and it generally becomes stable there, maintaining a cabin temp of about 70 degrees.

Any ideas? Bad thermocouple in the sensor? I know a thermocouple can drift like that.

E55AMG2 · 10th December 2005, 01:24

Quote:

Originally Posted by erkq

I did a search about this and didn't find anything so...

My climate control drifts colder as I drive. I bump up the setting a few degrees at a time to maintain a comfortable temp. At the end of about 45 minutes I'm at 89 degrees (F) and that usually does it. Sometimes I have to go that last step to 90. Then I get a LOT of hot air. Go back to 89 and it generally becomes stable there, maintaining a cabin temp of about 70 degrees.

Any ideas? Bad thermocouple in the sensor? I know a thermocouple can drift like that.

do you use the dial in between the middle air vents?

Digi · 10th December 2005, 01:35

Quote:

Originally Posted by erkq

I did a search about this and didn't find anything so...

My climate control drifts colder as I drive. I bump up the setting a few degrees at a time to maintain a comfortable temp. At the end of about 45 minutes I'm at 89 degrees (F) and that usually does it. Sometimes I have to go that last step to 90. Then I get a LOT of hot air. Go back to 89 and it generally becomes stable there, maintaining a cabin temp of about 70 degrees.

Any ideas? Bad thermocouple in the sensor? I know a thermocouple can drift like that.

Unusual heater functions in general (no fan, no temperature control, wide variations in fan or temperature setting, and otherwise wacky behaviour) is almost always the final stage resistor. This is a very common problem on all BMWs. This would be the first part to replace.

erkq · 10th December 2005, 01:36

Quote:

Originally Posted by E55AMG2

do you use the dial in between the middle air vents?

I leave that rolled all the way up to red (hot). The cold air comes out of the other vents too. Of course more cold air comes out of the center vents if the dial is rolled down.

erkq · 10th December 2005, 01:38

Quote:

Originally Posted by Digi

Unusual heater functions in general (no fan, no temperature control, wide variations in fan or temperature setting, and otherwise wacky behaviour) is almost always the final stage resistor. This is a very common problem on all BMWs. This would be the first part to replace.

So that resistor is behind the glovebox? Do I remember that correctly from other threads?

Digi · 10th December 2005, 03:14

Quote:

Originally Posted by erkq

So that resistor is behind the glovebox? Do I remember that correctly from other threads?

Here's a link with pics and instructions:
http://www.540i6.com/finalstagereplacement.html

KBK · 10th December 2005, 06:26

The hilarious part is when, in the winter, you put a hot cup of coffee in the cupholder, because you are trying to warm up.

Then you freeze, as the temp sensor..is directly beside the coffee cup...and the temperature in the car goes way down.

What doorknob designed that?

erkq · 10th December 2005, 07:39

Digi: Thank you for the good info. I will try it.

KBK: Absolutely... a doorknob indeed. I couldn't believe they didn't think that one through. Not only what you say, but the cup holders are too small to hold a coke bottle... they only fit a can. PLUS they are so low on the can it can easily tip over if full. PLUS you have to clear the very handy tray underneath of all your change, pens, papers, etc. before you can use it.

I think it's funny. A very quirky oversight that gives the car some character. It can't all be pefection.