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  View original topic: Repaired my AFM
daroota Mon Apr 14, 2014 10:20 pm

Here's how:

I was having problems, the van was dying when throttling up the rpms

I removed it and tested the Ohms according to the bently and got the following:

Pins:
6/9: 260ohms resting But intermittant
Up to 1500 when moving
7/9: 320ohms resting usually wouldn't read at all
Up to 600 when moving
6/22 2540ohms
@16ºC

The book recommends @ 16C (66F or so)
6/9: 560ohms
7/9: varies
6/22: 2300-2700


My AFM was opened by a previous owner. I removed it from and cleaned out some extra RTV mess!

Found the little flex metal connecting to the copper arm wasn't always touching, so I bent it a little closer.


but that wasn't enough.

I removed the 4 screws from the side where the harness connects and removed the connectors from the inner workings.

I cleaned the surface with a PINK RUBBER ERASER, then cleaned the the external pins the same way.... pretty much wrecked the eraser, but hey they are cheap. (they make wonderful contact cleaners, I use them in sound equipment all the time)

And I was also having a problem with the connection of the harness. It would only run ok like this:



So I bent the inside contacts downward before putting everything back together.

Once together and installed, my harness didn't flutter when I played with it.

The engine rev'ed up nicely, and it turned over right away. (instead of choking out)

It's getting late out so I didn't let it warm up (it's 10 and it's air cooled and not so quiet)

But it ran well a few minutes without problems.

I Did not take apart much of the AFM, but I cleaned the carbon area (again, but I know it wasn't the problem)

Hope this helps someone else. It hopefully saved me a replacement afm!

Bosch 0 280 200 028 is my afm part number

IdahoDoug Mon Apr 14, 2014 10:40 pm

Nice tips, thanks.

Wildthings Tue Apr 15, 2014 3:03 am

You can get a piece of flexible copper braid and solder it between the fixed arm and the moving arm to get a better connection.

Also you can get acid free silicones to seal the lid so the fumes don't cause corrosion. I just use regular RTV silicone, but only smear a thin bead on the outside of the lid once it is in place and have never had problems. If you think you are going to be going back into the AFM any time soon, just use a few daps of silicone to hold the lid in place.

Ahwahnee Tue Apr 15, 2014 2:00 pm

Wildthings wrote: You can get a piece of flexible copper braid and solder it between the fixed arm and the moving arm to get a better connection...

Like this (only I did not use braid -- probably will have to replace it in a decade or two):



Also did the clean-up, lube, capacitor fix and a double bend in the arm to make it ride on a new track.

Steve M. Tue Apr 15, 2014 4:32 pm

You can also loosen the screws at the corners of the printed circuit board mounting plate and physically move the whole thing a little up or down to get the arm to ride on a clean/new area of the carbon strips.

Wildthings Tue Apr 15, 2014 5:03 pm

Ahwahnee wrote: Wildthings wrote: You can get a piece of flexible copper braid and solder it between the fixed arm and the moving arm to get a better connection...

Like this (only I did not use braid -- probably will have to replace it in a decade or two):

Also did the clean-up, lube, capacitor fix and a double bend in the arm to make it ride on a new track.

Note that if the added wire is too stiff it will affect the calibration of the AFM even if it does takes a decade to fatigue and break. :cry:

Ahwahnee Tue Apr 15, 2014 5:05 pm

Steve M. wrote: You can also loosen the screws at the corners of the printed circuit board mounting plate...

Maybe you can loosen those screws... I couldn't with force that bordered on 'about to do some expensive damage'.

Mine seemed to be more than just tightened, apparently locked in place with some unknown substance.

daroota Tue Apr 15, 2014 7:45 pm

Well, I didn't have to do the wire Braid.

The van runs well! No surging or failing.

I'm happy, I'm going camping this weekend :D

Steve M. Tue Apr 15, 2014 8:51 pm

Ahwahnee wrote: Steve M. wrote: You can also loosen the screws at the corners of the printed circuit board mounting plate...

Maybe you can loosen those screws... I couldn't with force that bordered on 'about to do some expensive damage'.

Mine seemed to be more than just tightened, apparently locked in place with some unknown substance.


the wise man knows when to stop!

daroota Tue Apr 15, 2014 8:53 pm

LOL, and that's why I stopped at the circuit board, touched nothing below the sweeper arm.



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