[Diy_efi] Jetronic - RFI

urq urq
Thu Mar 2 08:03:02 UTC 2006

> On this same topic, I have 1987 Volvo 760 GLE that has a related problem. 
> While waiting at a railway crossing, an electric train passes, and the 
> brake pedal will vibrate and then relax with ABS warning light coming on. 
> The immediate fix is to, at an appropriate place, switch off the ignition 
> and restart.
> I think you have given me a clue as to a solution. Put the ABS controller 
> in a grounded box, and use some ferrite beads on the leads.
> Comment?

... it is difficult to tell for sure, but since the ABS system is so prone 
to electrical noise from the other systems in the car (primarily ignition & 
charging), the manufacturers usually do a passable job of basic shielding 
from electrical interference... in my ABS-equipped Audis the ABS brain is 
under the back seat.  What may in fact be happening in your case is the 
noise is magnetically coupled ... I'd expect you'd get some pretty big and 
fast moving H fields in a high speed electric train.  If that's the case you 
may have a difficult time creating an effective shield.  The systems my 
company builds use strong electromagnets to move stages around, and they can 
cause the display on a standard CRT to get distorted.  We had to use 
something called a mu-metal shield around the CRT to minimize the effect.

I suspect you aren't the only one in your area to have experienced this ... 
perhaps you can pose your experience to a local Volvo dealer to see if it is 
something they've heard reported before ...

Steve B
San Jose, CA (USA) 

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