I am helping someone out with this.
The alternators are ok. 28V with engine running. Still the light is on.
It is suspected it is the Lamar FM03 which drives the lamp.
I found an SR22 “DC GENERATION” wiring manual (section 24.x only) online which shows this
but it doesn’t give any P/N for the “function module”.
Does anyone have any info?
What serial number range is the plane?
1005-1267.
The wire 112-22 is the one, but which component in the MCU does it go to? It is one of the Lamar boxes…
Not sure a circuit for the MCU exists out in the wild. Lamar are instructed to not sell the modules to anyone other than Cirrus. Well, Socata do the same, with various French companies under a similar contract, but at close to 10k this Cirrus “box” is ultra expensive. What a way to get burnt – a box with all those components, relays, whatnot, so a high chance of “something” failing, and it is “not repairable”.
Nice money 
This is the original Lamar MCU which was replaced by Cirrus’ own unit in later models. These original MCU’s are pretty bombproof by all accounts, and according to what I have read you can send the function unit itself back to Lamar for re-build rather than the whole MCU.
Best advice is to contact Lamar directly.
Someone did that and was told they are under contract with Cirrus to not repair them.
Obviously people do repair them. The internals are quite possibly very simple so even without a circuit diagram it is not hard to fix.
There could be confusion, but a search for the FM03 finds nothing of relevance, suggesting it is not a standalone product. Nothing on Ebay either.
