Friends,
In my former life as an Alfa Romeo owner, the topic of solutions to clean
and preserve the integrity of electrical connections was regularly visited
on our mailing list.  It seems that the gold standard for this type of
material is actually an official VW item, produced by a firm in Canada.  It
is called Stabilant, and at the time was amazingly expensive, but effective.
The solution is reputed to actually carry a current at low voltages, and
thus is able to bridge tiny gaps in electrical circuits associated with
oxidation and/or cold solder joints.  Di-electric grease and regular contact
cleaners do NOT have such a capability.
We discovered another firm that offers a similar product at much lower cost.
I have used Deoxit from Caig Industries with success.  You may wish to check
out their web site:  http://www.caig.com  as they have a variety of formulas
which might be useful
(No proprietary interest, etc. etc., just a satisfied customer!)
Cheers,
Larry Merin
87 Vanagon GL
Little Rock