There's two things I can think of that are the best suspects. The first is broken or frayed wires between the driver's door hinges. If the left rear speaker works, the radio is okay. Removing the dash to replace the heater core would not cause those wires to break. That would be a case of a common problem occurring from repeated opening the door. The wire still works one time, and it breaks the next time. It would just be a coincidence that happens when the truck is being worked on for something else.
The clinker is while both of those problems in the door can be caused by broken wires, it's highly unlikely both would break at exactly the same time. That leads to the next suspect. That wire harness running between the door hinges goes into the "A"-pillar, then down to where it connects to a plug. That plug could have been pulled loose by pulling the dash rearward. Normally that doesn't have to be unplugged, so the mechanic would have no reason to reconnect it at the end of the job. There could be a circuit in there for the cruise control too.
First, look for additional symptoms. Since the cruise control has switches in the steering wheel, check if the horn works or if the Air Bag light is on. If you have power windows or locks, check if those work in the left door, and if the driver's switches work.
Next, the fastest approach is to connect a scanner so you can view the "Inputs / Outputs" for the cruise control. That will show switch settings change when you press one of them. That will tell you if one is not working. I have a Chrysler DRB3 for all of my vehicles. That one also displays, "Reason for last cutout" for the cruise control. This is especially useful for intermittent problems such as when it kicks out when you drive over bumpy roads. It should list "Vehicle speed too low" because the car isn't moving. Go out on a test-drive above 35 mph, then switch it on and press the "Set" button. Now road speed is high enough, so if it show, "ignition switch off", for example, look for a power wire that is disconnected, or a blown fuse. If it shows, "Brake pedal pressed", suspect the brake light switch is misadjusted. Check the operation of the brake lights too. If the circuit is dead, the cruise control won't work. The cruise control needs to kick out when you tap the brake pedal. If the fuse is blown for the brake lights, the cruise control will never get that "cancel" signal. This is a safety measure that's built in. It won't set if it can't get the cancel signal.
The shop that did the heater core should be looking at this. If the cause is due to their work, they deserve the chance to correct their mistake.
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Tuesday, March 26th, 2019 AT 7:28 PM
