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Electronics expert ?

blade7

blade7

Well-known member
The track in my turbo AFM is worn through at the start of the wipers sweep. Maplins sell an electrically conductive tough surface silver paint at £11 for 3gm, is it possible this could repair the track or doesn't it work like that ? The company that repair AFM's void the warranty if the cover is removed and are cagey about what they do.
 
I'm no electronics expert! I'm not sure about the paint idea though, it may affect the resistance measured between the track and the arm, I remember years ago I took the cover off mine and cleaned it with contact cleaner, its worked ok ever since. There is a youtube 'how to' which seems pretty good here:
https://www.youtube.com/watch?v=-11J8XawQtc
 
Many years ago in another life, we fixed my AFM with a slight bending of the wiper arm, was still working fine when I upgraded to the Vitesse. If I was to attempt a better repair I wouldn't do so with paint, I think I'd do a little research into the resistance of the factory track and then find something suitable to replace it with. There are a number of possibilities, from the hobby side I'd take a look at the dolls house self-adhesive lighting copper track, there's also the copper track used by slot car racers, again this is self-adhesive if these two won't form to the correct curve? (I'm pretty sure that they will do so) the third option would be to use a copper sheet cut to the correct grid, this may be possible to draw up in CAD and get laser cut.
I'm sure that there are other options open to the DIY AFM repairer...:)

Pete
 
Thanks for the replies. I have moved the wiper arm up and down on the post previously to sweep on an undamaged part of the track, but that isn't the issue now. As I said the track is practically missing where the wiper rests at the beginning. What I was hoping to do was just bridge the couple of mm to the start of the undamaged track. How are the AFM refurbers overcoming wear on the track ? Just to clarify I'm not expecting this being a long term fix.
 
If you clean the area with alcohol,mask it carefully,mix the silver paintwell & apply with a steady hand from the break to the start,I can't see what damage it can do & personally can't see any slight difference in conductivity would affect things-it is after all just a fancy potentiometer.
 
The conductivity of silver is three orders of magnitude greater than carbon (so the resistance will be 1000x less, assuming you can paint it at the same thickness as the carbon film as well as the same width). I know that in these times "we've had enough of experts", but it's going to put your AFM out of calibration and lead to incorrect fuelling of some sort. I would expect that the AFM will register 'no airflow' for the section of the track that you paint over, which could lead to a lean condition.
I can only assume that to recondition they replace the entire potentiometer board, from a source of parts that's not available on the open market (a common phenomenon for this sort of thing). Then they recalibrate the AFM.
If the track was completely disconnected and you repaired it, the best you could hope is that the AFM goes from 'no reading' to 'incorrect reading'.
 
robdimond said:
If the track was completely disconnected and you repaired it, the best you could hope is that the AFM goes from 'no reading' to 'incorrect reading'.
Click to expand...


Probably the best bet to eliminate the AFM from the issue I'm having at the moment. So paint containing silver or Graphite ?
 
I spoke to ATP electronics about refurbing my AFM but when they couldn't (or wouldn't) tell me if they replaced the track as part of the £160 refurb I decided against it. I later found out that Promax outsource their refurbs to ATP. New ones are available from Porsche but close to £800
 
There are some comprehensive instructions for testing the AFM on Clark's Garage (see garage shop manual -> AFM operation and testing)
 
Monkeythree said:
blade7 said:
Monkeythree said:
I spoke to ATP electronics about refurbing my AFM
Click to expand...


Did they want money to test it, even if ultimately they couldn't fix it ?
Click to expand...


Can't remember, sorry. Best I can suggest is to give them a call and see what they can offer you.
Click to expand...


I think it was them that wanted £40 to test the AFM, and they wouldn't say if they could repair/replace the track.
 
robdimond said:
There are some comprehensive instructions for testing the AFM on Clark's Garage (see garage shop manual -> AFM operation and testing)
Click to expand...


Yes I have seen that, thanks.
 
I do have a brand new turbo one that came from OPC if anybody needs it. £300 delivered it cost me, would be looking to recoup that cost.

Cheers

Stuart
 
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