Tuesday, August 18, 2009

BMW 3 Series (E46) Evaporator Temperature Sensor and Dash removal DIY

Every car has it's share of problems. For Toyota's, it might be water pumps and weak CV axles, for Nissan's it might be motor mounts that prematurely crack and break, for Hondas, you might experience havoc if your timing belt breaks prematurely.

BMW's have their own set of issues. One of them is the A/C evaporator. Most often, these develop a leak and the cooling ability of your air conditioner quickly comes to grinding halt.

One of the reasons this particular problem is so annoying is because the amount of work (labor) it takes to replace one. It took us (myself, the owner and a very savvy mechanic) about 6 hours of total labor. If you're thinking about making this one a do-it-yourself (DIY) project, then you'd better cancel all your plans for the weekend! But... have faith, it can be done.

We followed the Bentley BMW 3 series service manual, which has very good photos and decent descriptions on how to take the dash completely out.

Here we have most of the dash components already taken out. The steering wheel has already been removed.

The A/C vent comes out by grabbing it with your thumbs and pulling slightly upwards and out to release the clips underneath.

Watch carefully how the A/C vent cable is installed before removing it.

You're going to end up with a LOT of screws. It might be a good idea to put the screws in a zip-lock bag and label each of them.

Removing the airbag is pretty straight forward. Just be careful where you store it, and make sure to disconnect the cable without breaking the plastic harness.

Here's a shot with the dash completely removed. You'll need some help taking it out. The center console and gear shifter are kind of in the way. We were able to remove it from the passenger side by turning it and guiding it out slowly. Watch the headliner during this operation, especially if it's in good shape.

This is the driver's side. The only tricky part here is the headlight switch wiring harness. You have to slide the white collar around in order to release it. This took me a little while to figure out, and the Bentley manual wasn't of much help here.

Notice all the wiring harnesses. Try to remember which one went where, but don't panic -- it's pretty obvious where everything plugs in once you start putting everything back together.

This is the one of the evaporator temperature sensors connectors. The actual sensor is on the other side, in front of the heater core.

The second sensor is near the riverside right foot well area. The while harness with the green and white wire is the connector. The actual sensor is behind the connector itself. Don't worry about where the other end of the green and white wire goes.

The steering wheel airbag has to be removed. This is the sport steering wheel, so you have to insert a little screw driver in the slits on the side of the steering column to release the air bag assembly.

The wiring harnesses here are different. First you release the collar of the harness then pull up to disconnect. Again, be careful where you store the airbag.

Here's a shot of the car with the dashboard removed. Looks pretty overwhelming, but it's not actually as bad as it seems. Just keep track of all the screws and harnesses and don't rush!

When putting everything back together, go backwards, and make sure you have all the wiring harnesses connected before screwing in each part.


  1. Ha ha. All because the Germans had to make an overly-engineered system that you HAVE TO program to a certain temperature. Can't just turn a dial for cooler/warmer, hell no! Good work though.

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  4. Couldnt agree more with that, very attractive article


  5. Thanks for your share! very impressive!

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  6. Ya BMW has own temperature issues, like AC, Vent tabs Related to Vent Tabs Now you can buy online tab no require to buy whole vent, It is cheaper than all.

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  9. How can I access the second sensor near the right foot well area? Do I have to take the whole dash off?

  10. Is the water cool to drink at the "riverside right foot well" ?