[worf]

This first post is more-or-less a placeholder right now. Short Story: I'm hunting an 80-90 mA parasitic current draw that seems to originate with the fan/flap ECU. Or, if the fan/flap ECU is not the problem, then there's a common failure mode with '87+ 928s that results in the fan/flap ECU not going into full standby mode.

I've tested 11 ECUs and 3 different 928s.

Below, are a couple pictures of the rev3 and rev4 boards for Alan to look at, 'cause he's interested. I'll post more when I have a few minutes of spare time.

[worf]

Rev/4 board:

[worf]

Rev/3 board:
(This unit had been opened before by someone using a dull butter knife. I have no reference for the Rev/3 board so...)

[Ed Scherer]

I always suspect electrolytic capacitors on aging electronics, especially those that live in hot environments.

I don't know if you still use RL at all, but I started a thread over there in 2017: Keeping old electronics going. Right in the first post, it demonstrates just how bad the problem with electrolytic caps can be. One of my initial examples was a failed APC UPS, about 20 years old at the time. Of the nine electrolytic caps I pulled (with no notable bulging, either), every single one was out of spec. Some, wildly out of spec.



So... never trust an old electrolytic cap.

Looking at those PCBs you posted photos of, though (I peeked, even though they were apparently only for Alan's eyes only), I see that the electrolytic caps are affixed with copious quantities of snot. Understandable, given the application. But it would make R&R more difficult.

You could do an initial test of the caps in-circuit using an ESR meter and then take it from there based on those initial results.