Bosch AFM Refurbish / Restoration Service! (Air Flow Meter) AFM's FOR SALE!

[Gregs///M]

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[Gregs///M]

For Sale: 325i M20 AFM, Electrically Refurbished

ITEM SOLD

Gone through full electrical refurbishment.
A bit dirty on the outside but inside has been cleaned. Has great feedback to ECM.

$80 shipped including refundable $20 core deposit for your old AFM.

[Jrey]

you dont mind if i can take a pic of the inner part of the AFM? im looking forward to getting mine redone but maybe the pic will give some answer and see if it looks bad to you, also im hoping that youll have some more eta AFMs, starting to get annoyed with a jerky acceleration that happens once in awhile

[Gregs///M]

you dont mind if i can take a pic of the inner part of the AFM? im looking forward to getting mine redone but maybe the pic will give some answer and see if it looks bad to you, also im hoping that youll have some more eta AFMs, starting to get annoyed with a jerky acceleration that happens once in awhile

Sure, you can post up on here or PM me. Either way, I've never seen an AFM that did not look severely worn.

[Jrey]

Sure, you can post up on here or PM me. Either way, I've never seen an AFM that did not look severely worn.

PM'd

[noid]

With the arm bent to be lower or higher on the plastic strip, wouldn't the arm travel a shorter or longer distance because the track is oval vs flat?

[Gregs///M]

With the arm bent to be lower or higher on the plastic strip, wouldn't the arm travel a shorter or longer distance because the track is oval vs flat?

I supposed on a very small scale yes. However, it will still be within Bosch specifications. Most important is to maintain voltage output vs flap angle, without any disturbance and to maintain linearity. This must be verified through a oscilloscope or other data acquisition hardware.

[überslowetaLOL]

Bought an AFM from Gregs///M and it went great. Shipping was fast and on time with no problems whatsoever. Just paid for it and BOOM it was at my doorstep shortly after in a neatly packaged box. I trust that he did a great job refurbishing the inner workings of the AFM and I would definitely recommend him to anyone who is looking to get one refurbished or buy one already ready to go :up:

[Gregs///M]

Bought an AFM from Gregs///M and it went great. Shipping was fast and on time with no problems whatsoever. Just paid for it and BOOM it was at my doorstep shortly after in a neatly packaged box. I trust that he did a great job refurbishing the inner workings of the AFM and I would definitely recommend him to anyone who is looking to get one refurbished or buy one already ready to go :up:

Thanks for the great review!

[Gregs///M]

Let's go $80 shipped for the 325i AFM!

[Gregs///M]

I've got a very nice M30 AFM for sale too. $100 shipped fully electrically refurbished. Pics will be up soon.

[Gregs///M]

I've seen quite a bit of conflicting advice on how to test your AFM's. There is even a few articles floating around the internet with advice, in my opinion, that is incorrect.

Debate: testing an AFM with a DVM (digital volt meter) VS. an Oscilloscope.
Note: digital volt meter and digital multi meter are considered the same thing.



A DVM does not nearly acquire voltage signal as fast as a oscilloscope. Let me explain this the best that I can.

Let's say we want to test for bad AFM. Customer reports they have severe "bogging" at idle speeds. So let's test with a DVM vs an oscilloscope.

DVM:
Measure voltage output while the wiper arm is moved from fully closed to half open. The DVM does not have the resolution of an oscilloscope so its averages the voltage over the time acquired. BTW, in general, DVM acquire voltage using three methods...max volts, minimum volts, and average volts. The DVM is going to provide you an average of the voltage acquired.

Therefore, with a DVM, the voltage feedback would appear to be within spec and you pass the AFM and return to the customer. Customer spends hundreds of dollars replacing other items and troubleshooting, etc.

Oscilloscope:
Measuring voltage output while the wiper arm is moved from fully closed to half open and displays this voltage difference over a time scale of say...10 seconds.

This graphs shows myself opening and closing the AFM from 0% to 100% nine times in a period of 10 seconds.

Notice the "dips" to zero volts. This is known as voltage drop out and is the reason why there is a sudden loss of power near a specific RPM range, which correlates to a certain speed range or air input to the AFM.

Also notice on the second curve that voltage drop out occurs near the beginning of travel and near the end of travel. It happens several times more over the period of 10 seconds.

But note: these drops to zero occur and only last a few milliseconds and even microseconds! A DVM CANNOT ACQUIRE NOR DOES IT HAVE THE RESOLUTION TO CAPTURE THESE MILLISECOND DROPS TO ZERO VOLTS.

I would fail this AFM and the customer would rest assured that he has found the problem to the solution.

So please, anyone reading this. Please understand a DVM is not sufficient to test a AFM. At bare minimum, a oscilloscope or data acquisition software must be used which has a resolution of microseconds or better. My oscilloscope can acquire data at a rate of Pico-seconds so it is more than sufficient to test accurately.

Hope that clears things up.

[Gregs///M]

Here is another bad AFM that I tested for a customer.


Notice now the voltage spans from 0 volts to almost 5 volts. This is 14 cycles from fully closed to fully open. Noticed the short duration drops to zero. This occurs in the microseconds and cannot be captured by a DVM/DMM. Only an oscillocope or data acquisition software will have the resolution to capture these drops to zero.

A DVM/DMM would only show the average as you move the wiper arm from fully closed to fully open. It would appear the AFM is good, when indeed it is bad.

[kmarei]

any exprerience with the M3 E30 AFM?
if i send you one, how much do refurbish it?
i'll buy a used one, clean it up externally and send it to you for the cleanup process
so my car can fucntion with my existing one
just want to know rough cost
thanks!

[Gregs///M]

any exprerience with the M3 E30 AFM?
if i send you one, how much do refurbish it?
i'll buy a used one, clean it up externally and send it to you for the cleanup process
so my car can fucntion with my existing one
just want to know rough cost
thanks!

I've refurbished many AFM's from BMW to Porsche.
Still $150 including $25 refundable core charge.