The HVAC module would be a good choice for causing some of these problems. The mode switch input goes thru HVAC module, More importantly the HVAC module is also one of the modules that is a terminating point for the MS-Can Bus.
Because almost all these things have to go multiple modules to complete the task, the other major component would be the Gateway Module or Diag Link Connector. This module is the transfer station between Can Messages that are different Can Busses. There are four major busses, HS1,2,3 (High Speed) and of course the MS (Medium Speed) bus. The termination of Can busses is usually 120 ohm between + and - on each end of the bus, The Gateway Module has a termination point for all the main busses.
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The IPC instrument Panel Cluster only has three hard wired inputs
- Fuel pump and sender unit
- Park detect switch
- Low washer fluid level switch
So every thing else goes across the communication network. Any module on the bus can cause issues with communication, so any connections are a key point for failure. Modules intermittently powering up or down could disrupt traffic.
A simple check one could make with simple skills (using a ohm meter) is check the termination value of all the major busses. Because, they all go to DLC you can use that as a point to back probe the connector for the correct values.
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You will need needle probes to back probe the connector, take care not to damage the connector in any way (don't use a lot of force). All the busses should measure 60 ohms(54 - 66) between the +
can lines, That would value for the two 120 ohm terminations in parallel. If one of these values is off, it may aid your local Ford team.
I get much of my diagnostic reference from alldatadiy.com
. It is a subscription manual service, a little bit pricey, but can sometimes be easier to navigate then just the written documentation for me.