What happens when the customer damages the truck or the part when attempting to replace the part? How is the warranty handled, how is the damage covered and how uncomfortable do you think it might be when the customer's expectations do not meet with what the truck manufacturer is willing to do?
I see an awful lot of damage caused by well intentioned customers attempting to fix something with a soldering iron. Sometimes the damage can not be repaired, which makes for an uncomfortable conversation... especially when the part is no longer available (for out of warranty units obviously)
Some NDA's also discuss as a condition of the NDA specific requirement and/or expectations related to service. For example, I have seen some that require either a HI-POT or leakage current test for any work done to the primary circuit, also a ground bond integrity test. This is for both safety and liability reasons, even though it's generally considered good service practices. Also, this is one reason why SMPS/class D amp modules often require replacement rather than repair, as the modules ship from the factory with each module (linked by serial number) traced to a whole battery of safety tests.
Thanks, but to be clear there are plenty of problems that we do require that the amp be returned to an authorized service center that is experienced and understands the revision history or can accept specific information that the manufacturer requires. There are some products that must return to the factory due to the complexity and nature of the products. Generally, the cost is less and the turnaround time is shorter than many of the field service centers, so it's not a matter of time or cost but to get the repair done right in the most efficient way possible. We also require NDAs from our service centers and have expectations as well.