DIY: BMW Air Flow Meter Refurbishment

Video tutorial on how to refurbish/rebuild the Bosch Motronic air flow meter. Similar procedures can be applies to other units of similar design which can be found of other vehicles such as Alfa Romeo, Porsche, Volkswagen, Mazda, etc. If you do have an older model AFM such as what is shown in the video, you can also do an update/modification which can make the unit more reliable. This involves soldering a wire on the arm and swipe/wipe arm to cancel out the rotating contact. This particular tutorial was done on a 1984 BMW 733i.

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Air flow meter testing: https://www.youtube.com/watch?v=hQYRep6K15k

Tools/Supplies Needed:
-contact cleaner
-razor knife
-7mm socket
-1/4" drive ratchet
-standard/flat screwdriver
-phillips screwdriver
-soldering iron
-solder
-short strand of 18 gauge copper wire
-5mm allen wrench/key
-paper
-lint free cloth
-small zip/cable tie

Procedure:
-spray the inside of the air flow meter with a sensor safe cleaner to remove any oil residue or dirt
-remove the plastic cover which cover the electronics by taking a razor knife, cut away the silicone, then using a standard screwdriver pry the lid away from the case
-once the case is removed, then clean away any of the older silicone, it should peal off with your fingers
-remove the two spade connectors going to the pinout plug
-remove the pinout plug by removing four phillips screws, then pull plug out
-if your air flow meter is a newer model, remove the spade connector on the arm as well
-loosen the 7mm bolt holding on the wipe arm
-you may need to separate the clamp portion with a standard/flat screwdriver
-pull the wipe arm upwards
-now you have direct access to all the contacts
-if you find that your temperature sensor is faulty, there is no part which can be purchased to replace that specific item but you can get a used air flow meter and remove the sensor from there or purchase a new unit
-the temperature sensor can be removed but removing the circuit board which is held in with four phillips screws
-the temperature sensor is held in with silicon, use a small wedged chisel, go along the side of the backside of the sensor and slowly pry it upwards
-installing a new sensor does need to be resealed in place using a sensor safe rtv sealant.
-using the paper, rub the contacts to ensure they are clean
-spray the contacts down with contact cleaner, then rub again with the paper
-finally rinse with contact cleaner and wipe away with a lint free cloth
-to adjust the wipe arm, pull the arm downwards towards the circuit board, and bend the other portion slightly outwards (this will move the wipe arm closer to the pivot point)
-test fit the wipe arm to ensure it does not rub on the circuit board or cause any issues
-if your unit requires an update, get a length of 18 gauge black copper wire slightly longer than the electronic cavity, strip both ends
-clean both surfaces where the wire will be soldered to
-using the soldering iron, solder one end of the wire to the stationary arm coming from the pinout plug, allow for it to cool down and secure the zip/cable tie
-reinstalling the pinout plug in the unit, then solder the other end of the wire to the wipe arm
-as for the idle screw, that required a 5mm allen wrench and the factory setting is three turns outwards
-reinstall the wipe arm and ensure it is tightened down firmly
-connect the spade connector and ensure everything is put back into place
-reinstall on the vehicle to ensure the unit is functioning correctly
-the unit can be adjusted, both the gear and that idle screw, but I recommend having the correct equipment to measure the vehicle's air/fuel ratio
-once you are satisfied, use a sensor safe sealant to install the cap back on

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