1998 BMW 318i Heater/AC Works On and Off


1998 BMW 318i with a bout 115,000 miles. Recently, the heater / AC started to malfunction. Originally, the system would shut down while I was driving. Shut down included the display shutting off. Now the display does not appear at all. What’s strange is, even though the display is off, the AC seeme to be on (e.g. there is very cold air coming from the vents. What makes this even stranger is the display will come on while driving, stay on for a few minutes, then mysteriously turn off.

Display isssues for your model were one of the most common. Normally the display gets replace with the approiate “coding” performed. I have seen a site on the internet where a guy shows you just which surface mount capacitor to replace, for under a buck.

Next in line for intermittent fan speed issues is what BMW calls a “final stage” no effect on display.

Here are some instructions that I posted on my web page for repairing what is most likely wrong with your AC control.


There is another, similar set of instructions on the web, but I put these up just in case the other set gets taken down.

I checked out the link provided for this. It is very rare for a .47uf ceramic capacitor to go bad. Since it seems to fix the trouble it appears to be the correct fix but I have to wonder what is happening with it.

Looking at the pictures, the original cap is not a ceramic one. It is a film cap of some sort. These have a limited lifespan. That lifespan can be greatly reduced if they are heated up much.

Thank you. I will try the repair as soon as possible. Your instructions will make the repair within reach of a non-technical repait person.