Author Topic: Is My AFM Working? (Read 5156 times)

ClayW · « **on:** April 22, 2012, 09:15:23 PM »

I measured the resistance across the AFM through pins 1 and 4 only to realize that I have no idea if the readings are correct. See this video for the results.

Do those readings look normal? If not, what should I do? Is there anything else that I should check?

Thanks in advance!

bmwman91 · « **Reply #1 on:** April 22, 2012, 10:30:56 PM »

Measuring the resistance readings will only make you confused. You will see the values go up & down as you open the door. The carbon track is a network of series and parallel resistances laser-trimmed to give precise output behavior.

Apply 5V across the 5V reference input & ground. A properly functioning AFM will give a nice, constantly-increasing voltage on the output pin as you open the door. It will probably range something like 0.25V to 4.9V.

ClayW · « **Reply #2 on:** May 20, 2012, 11:22:14 PM »

Quote from: bmwman91;112076

Measuring the resistance readings will only make you confused. You will see the values go up & down as you open the door. The carbon track is a network of series and parallel resistances laser-trimmed to give precise output behavior.

Apply 5V across the 5V reference input & ground. A properly functioning AFM will give a nice, constantly-increasing voltage on the output pin as you open the door. It will probably range something like 0.25V to 4.9V.

Can you tell me which pins are the 5V and ground?

bmwman91 · « **Reply #3 on:** May 21, 2012, 12:27:28 AM »

ClayW · « **Reply #4 on:** May 21, 2012, 08:02:13 AM »

Thanks for getting back to me on an older post.

Forgive my lack of knowledge in this area. Which of the pins do I give 5V? Also, is the ground the body of the AFM or another pin? Then across which two do I measure the resistance?
Again, I'm a bit of a newbie on this stuff, so I need it explained to me like I'm a 4 year old.

Thanks in advance.

bmwman91 · « **Reply #5 on:** May 21, 2012, 04:04:28 PM »

Put 5V on pin 1.
Pin 5 is ground.
Pin 2 is the sensor output voltage.

You want to measure output voltage. If you measure resistance, it will jump all over sporadically due to how the resistor network is trimmed.

ClayW · « **Reply #6 on:** May 21, 2012, 10:10:57 PM »

Thanks! As it turns out, my AFM is working! The range is from .24V to 4.93V.

In case anyone was wondering how I got 5V.....

monty23psk · « **Reply #7 on:** May 23, 2012, 04:46:39 AM »

how did you get 5v? Just wondering as many ways to do it.

ClayW · « **Reply #8 on:** May 23, 2012, 05:35:24 AM »

Quote from: monty23psk;112721

how did you get 5v? Just wondering as many ways to do it.

I cut the cord on an old car charger for a cell phone. Then I plugged it into a spare cigarette lighter socket and gave that 12V. The end result was 5V.

See the picture above.

monty23psk · « **Reply #9 on:** May 24, 2012, 09:44:11 AM »

cool. I can't see pictures as currently on a work trip and the proxy server blocks certain photo websites.

monty23psk · « **Reply #10 on:** September 27, 2012, 09:39:52 PM »

Clay, needed to bring this post back to give credit, just did this to get a 5v power source as I need to test my AFM. Thanks for the idea.

ClayW · « **Reply #11 on:** October 03, 2012, 08:24:15 AM »

Quote from: monty23psk;116292

Clay, needed to bring this post back to give credit, just did this to get a 5v power source as I need to test my AFM. Thanks for the idea.

Glad to help!

monty23psk · « **Reply #12 on:** October 03, 2012, 12:31:06 PM »

It tested fine on the output values so I need to move down the line. I am guessing I have a vac leak at the injectors due to fuel smell. Also need to check vacuum hose to FPR. This might be time to upgrade injectors.

ClayW · « **Reply #13 on:** October 25, 2012, 10:18:21 PM »

Quote from: monty23psk;116404

This might be time to upgrade injectors.

I have a set of rebuilt injectors that I never used. let me know if you're interested.

You can email me at clay dot weiland at gmail

I'm referring to a set of these. I bought them and ended up not using them. They are still in their packaging.