Electronic gremlins

Mike Arman armanmik at earthlink.net
Wed Jul 27 14:29:37 EDT 2005

>From: "rob hod" <rob3 at hod3.fsnet.co.uk>
>Subject: Re: Electronic gremlins
>  Very interesting mike, - For a while now on my '88 100 my digital clock
>backlighting has been intermittant with the lights on. (it should just dim
>when you turn the headlights on, but as often as not it just goes out).

>  it would take out the
>cruise control with it... Doh!
>Funny thing was that using the left indicator brought the speedo back to
>life temporarily (until I turned it off)! Anyway I suspected ingress of
>moisture and/or earthing issues. Certainly it seemed to be behaving itself
>OK again today.
>  However is it the case that this link in the cluster could be the problem?
>or part of the problem?
>  Cheers, Rob.


I'm not familiar enough with the instrument cluster on the '88 100 to know 
how similar it is. If it is the "new style" dashboard (padded eyebrow over 
instruments), there is a good possibility that this is the problem. If it 
is the "old style" more angular dashboard - (84,85, 86, 87?), probably not.

The problem is the various connectors are flow soldered all at once on 
assembly (with a "wave soldering machine")- if you get the machine hot 
enough to solder the big pins correctly, all the itty bitty diodes and 
resistors melt. If you keep the machine cool enough not to toast the little 
parts, the big parts won't heat up enough and you wind up with cold solder 
joints. This problem is not confined to car parts - I've seen it on plenty 
of other electronic devices, power supplies, etc.

Solution is to remove the PC boards from the cluster, examine all the 
larger, heavier parts with a jeweler's loupe (5x or so), and prepare to be 
amazed at how crappy some of the solder joints are. Using a 35 watt 
soldering pencil and some new, fresh rosin core electronic solder, just 
resolder the entire row - and anything else that looks suspicious. Add 
contact enhancer, reassemble and away you go!

Mike Arman
90 V8, not just a car, an ADVENTURE!

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