AFM (Air Flow Meter)

An AFM does exactly what its name suggests: it measures the amount of air that’s flowing through the inlet manifold into the engine. This way the engine control unit (ECU) can calculate how much fuel is needed in order keep the perfect air /fuel ratio and therefor the optimum mixture for combustion.

The AFM uses a clever system in order to measure the amount of air that flows through: It uses a wire that’s been heated by a constant current. This results in a constant resistance as long as the wire doesn’t cool down due to external factors such as flowing air: once the air starts flowing past the charged wire, it will certainly cool down and the resistance will chance accordingly. This way the ECU can determine how much air is flowing into the engine.

What if the engine warning light appears on the dash?

In that case there’s a failure in the engine management system (EMS) and it could be the Air Flow Meter that’s the problem.  Unfortunately many parts within the EMS could fail, so it’s key to first determine the source of the problem. If the AFM really is at fault, then you should check it on dirt or wear, because this will cause the meter to generate incorrect signals and thus influence the actual air / fuel ratio. This can cause the engine to lose power or worse. Cleaning it sometimes helps, but most times it needs to be replaced or repaired / remanufactured.

What does it cost to remanufacture an Air Flow Meter?

It’s actually a lot cheaper than buying a new part! Remanufacturing an AFM costs max. 50% of a new unit without losing out on quality or warranty. In case of a combined part, such as the ECU of the Mercedes-Benz A-Class the difference is even bigger. So remanufacturing really is a great deal. And on top of that, it helps to create a sustainable economy as well!

What reman company should I choose for the repair / remanufacturing of an AFM?

At the moment both BBA Reman and ACtronics are the largest and most thrusted companies in Europe, but there are other trustworthy specialists out there. Just choose the one that suits you.

Useful sources:

http://br.bosch-automotive.com/en/internet/parts/parts_and_accessories_2/electronics_and_accessories/sensors_17/hot_film_air_mass_meters_2/hot_film_air_mass_meters_6.html