Dim Lights
Nope haven't touched the wireing yet. With that said the previous owner hacked up all the wires to the stock stereo. But I don't think that would cause dim tail lights.
What everyone is trying to explain is that the wiring and connections ARE the very likley problem, and this is based on literally thousands of similar cases in the past. That is what you need to tackle in this case and cleaning/checking grounds is part of that; there is usually no 'just do this' solution for dim lights.
The reason is that when current flows through wires and connections, there are tiny amount of what is called resistance in each. If the connections get corroded or dirty, then the connection's resistance increases and the current flowing through them causes a voltage drop at each dirty/corroded connection. At the far end, at the lights, you end up with much less voltage than originally when everything was new.
The current from the alternator to the tailights has to flow through at least 8 connections on the 12v circuit, plus more connections in the ground circuit via the chassis, plus a switch contact in the headlight switch. Any of these can cause the problem and it is common for several of them to have minor voltage drops that add up.
Get yourself a voltmeter (you truly need one in your tool box for these cars when the wiring gets old) and check the voltage at the contacts of the lights that are dim and you find that the voltage to chassis ground at the dim light is much less than 12v. If low, then you check voltage at each connection from the light back working your way back to the power source (the alternator for a running car or battery is not running) and find where there are large voltage drops across a conneciton or switch.
Also, check the health of your alternator to make sure it is putting out the correct voltage. Measure the voltage across the battery terminals with the car warmed up and the car at fast idle; it should be 13.7-14.3 volts. If lower, that is also contributing to the dim lights.
Does the ammeter work in this car?
