Lights seem to go dim....?

[CW240Z]

So I got my Z running after sitting for a while and lately I've noticed at night that when I turn the headlights on, they slowly go dim until I rev the car up. The car has an older battery in it that will hold a charge enough to start it for about a week, could this be the answer to my problem or could it be the voltage regulator? I know it has a good alternator on it too. Also, my turn signals wont work at low idle, only when I rev up slightly they will work. Any ideas of what that could be? Are these problems from the same source? Thanks guys!

[SteveJ]

The best way to figure out your problem is to go through the troubleshooting guide in the FSM. Compounding the problem is that since the circuit that carries power to the headlight goes directly through the switch, over the years the voltage to the headlights drops, also dimming them some. The solution for that is to put relays in the circuit, such as the system designed by Dave Irwin (aka Zs-ondabrain) and sold by him and Motorsport Auto. (MSA has them on sale right now.)

[CW240Z]

Cool I'll have to read up on that, I'm planning on replacing the battery anyways and going through some electrical work on the car to ensure it's reliability. Thanks for the info!

[CW240Z]

Geezz that kit from MSA is a little bit pricey..... Would the voltage regulator even contribute to the dimming of the lights? I'm planning on putting HIDs in it so I guess ill need it regardless.

[beermanpete]

It sounds like your tired batterty is the problem. Since the lights get brighter when you rev the motor we know the alternator is working.

At idle the alternator does not have enough outpout to keep up with the headlights (normal). The battery voltage will begin to fall due to the slight discharge. After a while the lights will dim due to the lower voltage. When you rev the engine the alternator output increases, raising the voltage and the lights get brighter.

How long are you letting the engine idle? If it is only a few minutes while waiting at a traffic light you need a battery.

[CW240Z]

I'm hoping it's the battery as well since it has sat for so long. Ill start the car up for a while and lit it warm up before i drive it around the block ( car isn't tagged yet ) and after a bit of driving, if the car sits at idle the lights will slowly go dim. Once I get the brakes on my car situated, Ill get a new battery on it.

[FastWoman]

Dave's headlight relay harness is a great convenience, but if you're dirt poor and handy with a soldering iron (like me), then you can DIY with about $10 in parts. Here's how I did mine:

http://www.classiczcars.com/forums/showthread.php?35588-Upgrade-from-fusible-links-to-circuit-breakers&p=301787&viewfull=1#post301787

Post #35

The wiring on your 240 headlights might be a bit different, but probably not MUCH different.

[ajmcforester]

You might want to replace the battery sooner than later. A bad battery puts strain on the regulator and the altinator. What I've seen people do is replace the battery when it is really bad then two weeks later they need to replace everything but sometimes they go 4 weeks replace the alternator now the new battery is bad . . . I'd recomend getting the battery tested and replace if needed the soon the better it's cheaper that way.

[Bonzi Lon]

I see that yours is not legal yet, maybe get the other systems, brakes etc, working then address the light issue with a 'made for' or the DIY. I don't do wiring.

It comes down to, safety vs cost.

After my 73's refurbishment, I considered the lighting 'unsafe at night', was just like yours. I don't do wiring, so Dave's Harness was the only way. It performs as stated, looks great too, then you hide it.

Bonzi Lon

[jaltman]

I too have installed Dave's harness and love it. But the simple fact is that the alternator is underrated and at idle the lights dim and the heater fans slows and etc etc.

[tlorber]

You should look into the internally regulated alternator along with Dave's plug (this whole thread is starting to sound like a plug for Dave). This topic is discussed significantly on this site. My cost all in was around $60.00. This bypasses the old mechanical VR and provides a more stable, higher output. It is a simple bolt on, completely reversible, and takes about a half hour once you have the parts.

[H4LIGHTS]

The best way to figure out your problem is to go through the troubleshooting guide in the FSM.

Until this is done all other advice is really superfluous to the issue. First find out what is and isn't working correctly and fix.

Then after you have determined everything is OK, start upgrades one step at a time.

This will give you less grief and aggravation, but probably fewer new "help" threads on this subject.