Air FLow Meter

Mon Mar 14, 2011 9:35 pm

Hi folks, found a large cut in the pipe that conects the AFM to the throttle body, I've ordered a new one, so if this is not my running problem, it certainly is a problem to rectify. I have bench tested the AFM while it was off the car and found the potentiometer seems to work okay. My temp sensor on the other hand seems to output a constant 560ohm, even when heated with a hairdryer. I was caught sneaking the hairdryer from the house, so may have to employe a different heat source on the next occasion. Is there a good AFM test proceedure up anywhere? I would have expected 0 ohms or an open cicuit from a fautly temp sensor. Cheers.

Mon Mar 14, 2011 9:51 pm

Blue sensor when cold should show 7000-11600ohms,hot should be 270-400ohms.....according to my Bentley manual.

Would suggest you ask for a heat gun next Christmas!

Mon Mar 14, 2011 10:11 pm

Maybe so, but the hair dryer is less likely to melt anything!, no, I mean the temp sensor within the AFM itself, the reading is way off according to the bentley manual ( quoted for 20 deg. C ) but then the pinout does not correspong to my oown unit, with pins numbered 1,2,3 and 4. The one in the bentley manual has a pinout of 5,9 7 adn 8. Assuming the 9 is not a missprint. When I got the variable reading for the flap/potentiometer on two pins I assumed the other two were for the sensor. You will only see it when you seperate the AFM from the airbox.

Tue Mar 15, 2011 12:02 am

daimlerman wrote:Blue sensor when cold should show 7000-11600ohms

Might be if you live in Antarctica, but 4000 ohms is nearer the mark in the UK.

Tue Mar 15, 2011 12:10 am

Your IAT sensor reading is about right, whatever Bentley says.
To test the AFM, you need to connect a DC power source (6 or 9 volt battery) across the ends of the resistor track, and monitor the voltage at the slider as you slowly open the flap by hand.
The voltage must increase steadily, with no drop outs or reductions in voltage.

Tue Mar 15, 2011 9:40 am

Thanks for your replys folks, the IAT is at least 1k ohm to low according to Bentley, though I think the problem is with my test method. I measured resistance and not volatge in both cases. In order to establish the correct pins I'll have to snap open the sealed cap. I'll replace the hose first and see what this does for me. I will remove the TB and check the TPS this evening while I have all out, as per bentley. I don't think there should be a wiring difference on the TPS.