autocheck woes on 90 200

[Mike Posner]

Constant warning light for coolant level/temperature. Temp and coolant are
fine.
Prior post by Cobram indicates his problem was not fixed via replacement of
reservoir,

wiring check, multifunction switch. He finally replaced the board from a na
car, fixwd the
problem but had to sacrifice accurate boost measurement.  Has anyone fixed
this problem at the component level, i.e. resoldering , new caps or
resistors?  This is an expensive fix at the dealer, $700-$1,000 as I recall.
I think the lower price might be for a rebuilt unit suggesting
that some one knows how to repair thes board.   TIA   Mike Posner,
Encinitas.

90 200
83 coupe
89 Pontiac TTA
84 Volvo ICT 5 speed