1991 bmw 525i heater problem

[smuj]

Hi Folks,
could anyone advise on my heating problem with my 91 525i, non aircon. nothing but cold air out of the dash vents, windscreen and footwell hot or cold as dialled, fans work as dialled too. I think it may be a stepper motor problem to the dash vents? All advice welcome.

thanks

Smuj

[wayne5474]

Hi smuj

I have a BMW 525i myself and im having the same problem. We have changed the thermostat but it hasnt worked . I have checked the Haynes manual aswell but nothing has pointed to what the problem is... I will keep checking and if I find out what is wrong I will give you a shout.

[atv087]

hows your coolant level? also is your coolant system properly bleed i know when mine had even the tinyest bit of air in it my vents would blow cold. i have a 1990 525i so if you have any more questions let me know ive gone through hell with my car i just finished installing a new motor today.

[ShadeTreeBill]

Since it's only the dash vents that blow cold.... It would seem that it has to be a stepper motor (vent control motor) or wire going to that motor.

Since you do get heat from the defrost vents and foot vents, then you do not have any problem related to coolant or thermostat.

I would assume that this is a pain to fix as it would probably require disassembly of the dash to reach the vent system and stepper motors.

My 89 525i has a bad heater core (or other coolant leak) in the dash, and I am dreading that job... been putting it off for several years... do you smell coolant in the cabin when running the heater?

This might shed some light on the disassembly process to get to the vent system....

http://www.homeofsbc.com/Fixes/Heater/heater.htm

Good Luck!