heater not functioning on AUTO properly

[jayb]

Has anyone had this problem, and maybe a easy DYI fix (?). The heater on my 2000 328i is not delivering heat when in the AUTO position, it is blowing cold air. Unlike what it is designed to do, it does not wait until the engine warms up for the cool air to start flowing and continues with cool air after the car warms. BUT, if you use the SELECTION heat buttons for the dashboard position (middle) it works properly and immediately delivers heat at the right level. Push the AUTO and it goes back to cool air (with hot engine).
Is this the switch? A easy thing to get to? A DYI? A not uncommon problem?
Sounds like it is the heat AUTO switch or the mechanism that regulates the vent door to allow hot air to flow.

[dembooks]

.......it can be any of the choices you listed

for quick, accurate diagnosis, having yer
car hooked up to a BMW tester is the best route to go

it's not a DIYer - unlike a irratic acting blower
speed resistor.

make a date with your dealer.

[jayb]

there is a center button on the heater between the dashboard heater vents that rovolves between the red position (heat) and the blue position (cold). When you rotate that knob between red and blue does the volume of air flowing out the dashboard vent (next to radio)change when it is in the cool vs hot air position. I do not remember what was norm for my car 2000 328i. It now increases significantly when in the cool setting (blue) and very low in the heat setting (red). In other words, I can regulate the air flow by just rotating the switch between blue and red---when the engine is hot.

[zoomie35]

Mine did the same thing, it was the final stage resisitor. DIY in about an hour, less than $50. Works fine now. Google it, tons of info.

[dembooks]

yes - the middle red/blue overrides 'just slightly'
the main temp control temp settings
your only changing the temp out of the 'face' vents on the face
of the dashboard.

that does not effect the windshield or floor vent temps

your original description was related to temp/blend flap
regulation - not blower fan speeds
[img]http://i226.photobucket.com/albums/dd318/cd02md/E46blowerfinalstageresistorOLDvsNEW.jpg[\img]

[jayb]

yes we recognize that the red-blue dial does change the temp. BUT I noticed that it is noticeably changing the force of the air (flow) coming out of the vents depending on if it is on blue (cold) is is high air force, and when you go to red is drops to a much lower air force (flow). You can both feel the difference in flow, and hear it.
This is a second issue in addition to the lack of temperature issue
I though this may indicate source of problem? I also wonder if this is looped into the computer for control of heater speed

[dembooks]

.."I also wonder if this is looped
into the computer for control
of heater speed " = no - no effect on fan speeds

[dembooks]

has no effect on Temp Regulation - just blower fan speeds