Type-44 instrument cluster: intermittent high boost reading

[Ameer Antar]

You may remember a while ago I had high boost gauge readings like 1.4 bar with
engine off and 1.0 at idle. That problem has been recurring, but I just had to
tap the cluster and it would eventually settle down. 
 
While I was opening up my spare instrument cluster, I noticed a little bit of
green corrosion on one of the capacitors on the main board under the
tachometer. Definitely not a good sign. Since I had the dash apart for my
cruise control tests I figured I should check the one in the car as well. I
took a look and the same capacitor had puked some of its guts out and had
corrosion on some of the surrounding solder pads. When I took it out I saw that
the upper contacts of the board had almost totally been destroyed. I cleaned
the traces and replaced the cap with the same 10uF 35V value. I made sure to
widen the upper traces and use plenty of solder to make full contact with the
upper traces. I replaced the other electrolytic cap for the microprocessor 5V
power supply while I was in there. That one looked fine, but I figured why not
since electrolytic caps tend to deteriorate relatively quickly. That one was a
100uf 16V cap.
 
I'm not sure why the smaller 10uF cap broke down before the bigger one,
especially since the smaller had a higher voltage rating. In any case, it looks
like that problem may be fairly common since both of mine had it (although only
one had problems with the boost gauge). I'm glad I caught it when I did because
there wasn't much left to the circuit traces. After the fix I don't have to tap
the glass to get the boost gauge to read right and it looks like my readings
are a tiny bit higher now. If you have any symptoms, or even if not, check
your's out if you have the chance.
 
-Ameer