03-03-20, 04:56 PM
This is my proposal on how to fix the broken fan activation w/o removing any old parts.
New parts are added on the lower side of the board, no need for complete disassembly, removing the lower compartment of the dash is sufficient.
The circuitry around TR34 is copied and put in parallel to the existing one. This should be fine as it only serves as a simple switch to ground for the relay activation.
Unfortunately there are a few more components to be added than simply TR34.
The replacement parts are best guesses by taking the marking codes, package type and estimated currents and voltages required for this application into consideration. All are non-SMD.
Replacement for TR34 is BC639, 1A/80V.
The proposed diode is a standard 2A/400 silicon type (most likely oversized).
Resistors are uncritical, smallest package with 200mW rating should be fine.
I'm open for discussions and opinions about this solution.
New parts are added on the lower side of the board, no need for complete disassembly, removing the lower compartment of the dash is sufficient.
The circuitry around TR34 is copied and put in parallel to the existing one. This should be fine as it only serves as a simple switch to ground for the relay activation.
Unfortunately there are a few more components to be added than simply TR34.
The replacement parts are best guesses by taking the marking codes, package type and estimated currents and voltages required for this application into consideration. All are non-SMD.
Replacement for TR34 is BC639, 1A/80V.
The proposed diode is a standard 2A/400 silicon type (most likely oversized).
Resistors are uncritical, smallest package with 200mW rating should be fine.
I'm open for discussions and opinions about this solution.