The fuses can be very deceiving, at times, and they should be pulled and physically inspected. I had several with hairline cracks at the ends from the PO "spinning" the fuse to the point of wearing through the thin metal. Also, aluminum fuses are notorious for being intermittent.

For the pushbutton controller, you didn't mention where the failed connection was, but the area that usually causes problems is the edges where the boards come together in an "H" pattern. Mine had hairline cracks and even checked good with a meter but caused intermittent problems when the boards "flexed" from enabling the pushbuttons.

If your failure was a sudden event, I would be looking at fuses (There are two.) If it is intermittent, then it might be the pushbutton controller.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )

It probably can be rough enough with electronic knowledge with that unit. I see that a problem with the acessory water pump for the heater can burn out things in the controller. Call that a common failure. So check the operation of the water pump by feeding it with external voltage.

Actual current drain should be monitored but if working a fuse addition in the power wire to it is recommended.
That or some other defect may have burnt the trace open .The ccu appears to be a real pain in the posterior. It is very remote chance that the trace opened without excessive current present. Without a lot of working electronic experience I would suggest another approach.

It sounds like a comprehensive manual and wire extensions to get it into a position to work on would be required. Like most electronic devices certain failures are common. That is how money is made in that business.

If you had to seriously troubleshoot everything that came in the door both profit per unit would be lower and the cost to people would be higher. I have never read or heard of the common failures with that actual device posted anywhere. So the electronic /electrical portion is really not serviceable by the average guy.

The cruise control has had enough exposure that the average guy with some electronic ability can recondition it if he wants. This resoldering things is in general marginal at best and a reflection of poor design/build quality. They used a pathetic quality of condensor in the cruise controls.

Again before any serious service on the cruise amplifier. The actuator has to be determined not to be the causitive of the cruise amplifiers failure as well.

Another alternative for repair is General Development Laboratories who remanufacture the pushbutton controllers (~$185 which is a better price than ~$400+ aftermarket).

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )