Alternator weak?

[Flash]

I don't think that's low voltage but would check the ground on the engine if you are having problems then change the voltage regulator. It's also possible to have blown a diode in the alternator (back half of the case) but I don't think that's the case in this situation.

Copy I'll check resistance on the ground. Can I check the voltage regulator or can only swap it?

 

[Flash]

Are you sure it's 13.5 volts because everything should work fine at that level?

That's what the multimeter read at the battery at idle. But the turn signals slow down and headlights dim also.

 

[Flash]

Just your opinion of course. However, you are somewhat correct. No one NEEDS to, but it is an option as stated.

Agree with @PlymCrazy that this dimming behaviour is normal with an aged charging system. This is where using relays can help.

As for the headlights turning off, I would check what @Don Frelier said. Good luck.

You said an aging charging system. What would I need to modernize I guess? New wiring and high amp alternator?