Question1997 BMW 318ti. The a/c vents (on and off) recently developed / have an odor similar to old urine -- which could be a lot of things with the a/c -- or the vents. Any pointers on cause and how do you fix it? Also how do you replace the cabin air filter on the 318ti?
Thank you
Frank
AnswerHello Frank,
With time and usage aircons whether home or car unfortunately develop smells. The most usual is a musty odor. Next would be the accumulated smells of the room or car's interior.But old urine? To diagnose whether the smell comes from inside the
evaporator and microfilter or from outside, run the AC on in both recirculate (no air from outside getting in) and with outside air intake open. Smell which is worse. My point is that the outside air intake area including the microfilter
may have accumulated a lot of debris. Some engine compartments have even been the favored home of some rodents
and I am sure you know how bad rat urine can smell.
If the smell comes from the evaporator itself, then the most that you can do is to spray deodorant into the air intake(with the microfilter removed but the filter housing
cover closed). Or, at your own risk instead of deodorant, use one of the chemical solutions that can be bought from auto supply stores specifically for cleaning evaporators.
Of course replacing the microfilter is a must. If possible also clean out the area immediately before and leading to the microfilter.
Replacing the microfilter itself is a little complex. It involves removing the glove box, removing the right lower (dash)trim cover immediately behind the glove box, removing
the footwell airduct, loosening the control module box and lowering it down,turning the knob that locks the microfilter cover in place, and finally removing the microfilter. Then if you can, vacuum the chamber that the microfilter came from.
It is not an easy thing to do. Only a very patient man
with contortionist leanings would enjoy it. If you need more info please do not hesitate to ask. Have fun!!!
