F I Air Flow Sensor

W

wallywest

Low Mileage
Hey Folks;
Does anyone have any detailed technical info on the Bosch Air Flow Sensor used in the fuel injected cars? The schematic I have implies that the resistance between 7 and 8 (or 7 and 6) is proportional to the air flow but I tried measuring it and the resistance seems to rise and then fall again. I opened it up and it looks very peculiar - resistors printed on ceramic (that's 70's technology for sure) but I can't work out what it is supposed to be doing. It appears to be a continuous resistor and moving contact - like a regular potentiometer - but with a bunch of fixed resistors connected at various points along the way. There are lots of unconnected bits so the part was clearly made for more than one purpose.
HELP???
/wallywest
 
Years ago, when I tried the RX-7 Nippon-Denso version of the Bosch L-Jet AFM, I found basic schematics that indicate the path through the potentiometer, but nothing that give circuit-level specifications. Bosch wouldn't publish that level of detail. You'd have to find someone who may have reverse-engineered it for that, I think.

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What are you trying to accomplish?
 
I have an original Bosch service instruction manual for the L-Jet system. If I can locate the book I'll see if it offers anything, but I doubt it says much more than what the function of the AFM is.
 
Dr.Jeff said:
I have an original Bosch service instruction manual for the L-Jet system. If I can locate the book I'll see if it offers anything, but I doubt it says much more than what the function of the AFM is.
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I have a digital version of that. Like other Bosch manuals, they may cover design and function, but they don’t provide schematics for their circuit boards, for obvious reasons
 
Hey Wally, I don't know if you already found your answers. But here is a explanation on how to test the AFM circut board. Scroll down toward the bottom of the page. It has a diagram and description how to measure VOLTAGE at the pins (connector terminal). So you will have to feed a 12V supply to do it (see the article):
http://www.gomog.com/articles/AFMadjust.html
 
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