[T3] I think I found my stalling problem!

[Jim Adney]

On 20 Nov 2023 at 19:43, Keith Park wrote:

> I had this happen to me 15 or 20 years ago, just died without warning
> coming out of work, no fuel pressure, Swapped brains and all was well,
> fixed the failed one and it was fine, thatTMs when Jim told me of this
> problem, Only problem ive ever had with a brain.

While Bosch probably used the same, or similar, transistors over the years, 
they mounted them to the PC board in ways that changed over time. At first, 
they used a tall plastic spacer between the board and the transistor, which 
allowed the led area to "breath."

After a few years they must have had some failures that led them to add a 
heat sink on top of the transistor, requiring a thinner spacer because of the 
lack of headroom above the transistor. The first spacer they used was a red 
cardboard spacer, but that one appears to hold moisture and hold it against 
the leads. Those are the brains that tend to have problems, especially in 
damp climates.

Eventually, Bosch went to a thin plastic spacer, with tiny bumps that allowed 
that space to breath. I bought some of that style for repairs, and I have 
suitable transistors for replacements.

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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