Hello,

This is a car with 20 year old electrical connections exposed to the environment. You will find this is most likely more than one single thing.

Things to check and possibly replace:

Check your battery terminals, especially the condition of the wires going into the terminal connector and the inside of the terminal. There should be no green, broken strands, or loose wires. Inspect and clean the negative terminal and look for the same sort of problems. Make sure you have a good clean connection to the chassis and the block on the other ends. Remember current needs equal paths, sort of like water in pipes. You can great big pipe with lots of water pressure going in, but if you have a tiny pipe on the drain that is the limit of how much water you can move. Electricity works in a similar way, the system needs to have a good strong connections on the plus and ground connections.

This next part, the negative battery terminal is off!

On the plus battery terminal there is a red wire that goes to a terminal block close to where the 25 Amp fused lives or lived. It is under a black plastic cover and is where all the power is distributed into the car. While replacing the engine harness in Inga found that wire was darker and discolored near the spade lug connector crimp. It was also very stiff near the crimp, a sure sign of heating from current. The block terminals were all badly tarnished. Replaced all the battery terminals with a no lead solder terminals and new wires everywhere. Added a new 14 gauge wire to the terminal block and the plus terminal, used a big yellow terminal ring lug on the battery end and a new spade lug on the other.. Took the entire terminal block off and used an eraser to put a shine on all of the block lugs. Replaced all of the spade lugs connectors with new ones, make sure you have good bright wire strands under the lug before you crimp. Good tip is to make sure you only remove the insulation, you do not want the have a cut into the strands of wire under where you strip the wire. That will lead to wires breaking and loss of conductivity or even a broken crimp later. Reinstall the connector block and plug it all back up. Put the cover back on and you are done with that part. Do not sand, grind, or rough up the surface of the copper connectors. That will solve any connection problems short term. Down the road you invite a lot more corrosion to form even faster. Use a mild abrasive like a Pink Pearl Eraser, maybe a white eraser for the areas. Files and sandpaper are quick fix band aids that you will pay for later in even more corrosion.

Then you find and inspect all the ground connections to places like the near the back of the headlights and washer motors. Just like before, there should be no green or chalky white wires in the crimps, no black or discolored connectors. If in doubt change them out by cutting the old one off and replacing with a new terminal of the same gauge and diameter.

Go to your fuse box and open her up. All of those copper terminals need a good shining where the fuse ends make contact, Good time to check and replace any tarnished fuses also.

One more place to check is the inside the car on the upper right had side of the dash that all those ground connections are tight and make good contact.

You do all that I bet you have no more issues with the dimmin of the lights.

Good Luck and keep the light on,

PT