As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TKS DEICE SYSTEM PRESSURE SWITCHES ARE FAILING IN THE OPEN POSTION. WHEN THE SWITCHES FAIL OPEN THEY CAN NOT ILLUMINATE THE DEICE PRESSURE FAIL LIGHTS ON THE ANNUCIATOR. THE LIGHTS ILLUMINATE TO INDICATE LOW PRESSURE. THERE IS NO WAY TO TELL LOW PRESSURE IN THE SYSTEM WITH THESE SWITCHES FAILED OPEN. WE HAVE REPLACED THREE SWITCHES IN THE ENGINE DEICE SYSTEM, ALL FAILED IN THE OPEN POSITION ON THIS TKS DEICE SYSTEM.