The Wheatstone resistor bridge is asymmetrical and a voltage appears which is submitted to an amplifier and directed to raise the wire temperature. Constant temperature of approximately 100 ºС is maintained by increasing or decreasing the electrical current flowing through the circuit while the incoming airflow cools the wire.īy increasing the airflow, platinum wire gets cool and its resistance decreases. Heated platinum wire, suspended in the engine’s air stream (3), is one of the legs of a Wheatstone bridge. Operation of MAF is based on the principle of constant temperature. Hot wire (2) with diameter of 70μm is mounted in a measuring tube located before the throttle valve. MAF sensor which measures the mass of air flow – Hot Wire sensor This type of sensor is not sensitive to the pulsations associated with opening and closing of intake valves and the output reading does not depend on the density of incoming air. Nowadays the most common are MAF, because they don’t have mechanical moving parts and have great performance and accuracy.
A sensor which measures the mass (kg/h) of the air flow – Hot Film MAF (HFM). A sensor which measures the mass (kg/h) of the air flow – Hot Wire MAF sensor (also known as HLM). A sensor which measures the volume (l / h) of the air flow – Vane Meter Sensor (VAF and also known as LMM). Sensor’s output signal frequency or duty cycle depends on the air consumption – HFM sensors. Sensor’s output signal voltage depends on the air consumption – VAF and Hot Wire sensors. 2 shows the MAF made by GM.Īccording to the principle of operation are: 1 shows the MAF sensor made by BOSCH, and fig. MAF usually is placed after the air filter and before the throttle valve in the air flow sucked into the engine.įig. Air consumption is one of the basic parameters for calculating the necessary amount of fuel. The sensor for volume consumption of air is used in many systems for management of engines for measuring value of the transitory cost of air. It is intended to be insensitive to the density of the air. By eliminating the need to replace the plastic housing, Delphi is providing a greener, 20% more cost-effective approach to repair.A mass air flow (MAF) sensor responds to the amount of air flowing through a chamber containing the sensor. Delphi’s sensor-only alternative allows the technician to focus on the part needing replacement. Once the sensor probe is replaced, continue reinstalling the completed MAF sensor assembly into the vehicle as you would normally.ĭelphi launched its MAF sensor probe as a green, less costly alternative to the traditional MAF assembly repair.Īccording to Delphi, in most cases, it’s unnecessary to replace the complete part since it’s the electronics on the sensor probe that fail 98% of the time. Place the MAF assembly on the bench with the connector down and push firmly on the flow tube to seat and latch the sensor probe. Slide the new sensor probe into the flow tube with the latch tang up toward the slot end of the tube.Ĩ. Handle the sensor connector only (never touch the electronics as this may damage the sensor probe). Carefully open the sealed new sensor package. Remove the product key and slide out the old sensor by grasping the connector. Pry on the sensor rim until the O-ring is out of the flow tube.Ħ. Insert a small 1/8” screwdriver into the gap between the circular rim on the flow tube and sensor. Gently depress the product key in the slot.ĥ. The tab on the product key should be nearest to the connector side of the slot. 
Place the key into the center slot of the MAF sensor assembly. Remove the product key from the bottom of the new sensor probe package.Ĥ. Place the MAF assembly on clean workbench with the center slot facing up.ģ. If there are no cracks, follow the remaining steps to replace the MAF sensor probe unit.Ģ. If there are, you will need to replace the entire unit not just the probe. Inspect the flow tube to ensure there are no cracks in the plastic housing.
Once it’s determined the mass air flow sensor requires replacement, the same servicing procedures are followed to remove the failed sensor assembly.ġ. MAF sensors can be installed two ways: as a complete unit including the flow tube or as a probe-only design as the ones available from Delphi, which provide technicians a greener, more cost-effective option, said the company.
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