Ok, I just added a aftermarket cd player to my truck. I wanted to ground the negative wire from it to the actual truck instead of the negative wire from the wiring harness. Problem was that NONE of the metal behind the dash was grounded. I tried every piece of metal I could find (all the way to the steering column, firewall, ect.) and nothing completed the circuit on my test light. Is this normal, because I have been having problems with the heater core (on my 5th one in about a year) and Ford blames the problem on a bad ground.... but they said they fixed it. Should all that metal be grounded and this could be part of the bad ground issue?

 

Sounds more like operator error. If the firewall wasn't grounded, the engine wouldn't run & the cluster wouldn't work.

The wiring harness ground wires go to the firewall grounds anyway, so just use them. It'll be fine.