E34 535i M30 AFM test

[E34jm984]

Was told to test my AFM for ohms and looks for spikes to see if it is working properly. Which of the 3 prongs is + - ? what values should i see with the door closed vs door open ?

[demetk]

I test my AFM's with a multimeter set on DC voltage. I find it's a better test since the signal going to the ecu is an output voltage based on an input voltage of 5 volts.

[E34jm984]

Okay i can do both, but which of the 3 prongs are + - ? Im trying to figure out if my afm is my intermittent issue ive been having. Could be a damaged wire in the actual sensor plug but havent found anybody selling one and no luck so far at junk yards. Considering just repairing it myself

[ross1]

Do your sweep using terminals 2&4
I don't have any spec but you are looking for a smooth increase in resistance as the vane opens

[E34jm984]

Thank you, that is what i was told to look for, is it safe to check volts on the plug going to the computer ? The wire has a small cut on the insulation but no wires exposed, i know that means it could still be bad though

[ross1]

Thank you, that is what i was told to look for, is it safe to check volts on the plug going to the computer ? The wire has a small cut on the insulation but no wires exposed, i know that means it could still be bad though Unplug the meter and use an ohm meter and those terminals, they are marked on the meter at the connection

[shogun]

Please post details what you measure here, then we have some data for the future.

[demetk]

Here's my idle voltage (89 535) with a 650 idle rpm.

http://i31.photobucket.com/albums/c375/demet_/e34/afm_baseline_v_2.jpg~original

[E34jm984]

Unplugged afm, got my mumtimeter set to 20k ohms, positive lead on terminal 2 and negative on terminal 4, got .08 ohms door closed, and .80 ohms door open, no real spikes it raised up pretty gradually.

If for example the afm is my problem, would i have noticed the spikes still even though its a intermittent problem ?

Also on terminals 1 and 3, i get 3.2 ohms

[E34jm984]

Please post details what you measure here, then we have some data for the future. today i am getting a chance to use a snap on vantage on my car so i will be testing the afm this way, will post pictures if possible but will come back and share what i find.