MAS strip down (large pics)

[GrahamC230K]

Guys,

You may remember from this thread all the problems associated with a faulty MAS.


Well, a few days and £7 later I have the correct tool to get the security torx screws out to examine what a MAS looks like close up.

Whatever killed my MAS it wasn't dirt!

 

[Steve_Perry]

Thanks for posting pics Graham, very interesting.

From what I've read, a fixed current is passed through the exposed wire and this in turn will heat up to different temperatures depending on the volume of air flow over it. A signal is sent back to the ECU and this is translated into a mass flowrate of air entering the engine.

Yours looks filthy doesn't it?

S.

 

[Andy W]

Surely some boffin in the electronics industry can identify the resistor type component and I bet that they are available for a couple of quid making MAS units reconditionable. I had a thought this morning while working on a Ford Scorpio Ultima, this car had a air mass sensor, surely some sensors must operate on the same principle or resistances making you able to buy one for say a Ford Fiesta, removing the resistor and mounting it to a Merc MAS body.

 

[cmgdaug]

So Graham, which is the wire that is directly in the air flow doing the measuring ?

Is it possible to mark the photo with an arrow ?

Thanks.

David Williams
E320 Coupe 1995 (W124)

 

[GrahamC230K]

Originally posted by cmgdaug
So Graham, which is the wire that is directly in the air flow doing the measuring ?

Is it possible to mark the photo with an arrow ?

Thanks.

David Williams
E320 Coupe 1995 (W124)

2nd to last photo.

 

[Dieselman]

The component shown is a Zener diode to maintain a set voltage.
This is not the problem with the Mass sensors. I believe they work as previously said that an element (hot wire) is heated to a set temperature and the current required to maintain the temperature varies depending on how much and how cold the air passing over it is.
I believe the "hot wire" burns out!

I've just gone and pulled the mass from my car. There is no diode attached at all so presumably no voltage biasing required.

The workings are inside the sensor unit and it needs pulling / breaking apart to see more.

Graham as yours is duff already are you prepared to pull it apart for us to see?

 

[GrahamC230K]

There are no seams or anything for me to prise apart, so bar taking a saw to it, not much I can do......

 

[Dieselman]

If you look closely you can see the two parts to the casing over the hot wire area and the amplifier board is under the cover that is held in place with the silicon seal.