Ok i know this is a question straight out of newb central but it's been on my mind for a while and you are the guys to answer it. When i fire up my 240 i notice that the lights although bright are dim compaired to when i rev the engine up. Also the wipers are slow until i hit the gas. Now i know that the faster the engine turns the more power the alternator puts out, but why do i not get the same power at idle. My other cars (30 yrs younger) have no disparity in power from idle to higher rpm's. Is this common with early Z's or do i have a slight problem that needs to be addressed. The alternator is brand new and so is the coil.

It is possibly the voltage regulator that needs to replaced. The alternator should put out pretty close to the same voltage all the time, it's the voltage regulator that controls the output to the battery and various systems. They can be adjusted but most people just replace them as they are not expensive. You can probably pick one up at Pep Boys etc. for under 20 dollars. Try that and see if that helps.

Welcome the 240! Y ou have just ask the same first question we all did.The more rpm the brighter is a 240 thing.The specs for the alternator show it 's charging ability begins at 1000 rpms.You could increase your idle.Thats to high for me.I do have a theory I'm working on.I believe you could change the pully on the alt. to increase it's rpm without the cars rpm increasing. Daniel

Well,my pulley swap theory is no good.Seems if you swap the pulley making the alt. faster that in turn increases the strength of the magnetic field within the alt. That in turn puts more load on the engine which would effect your idle.Also having the additional load at idle could cause the alt. belt to slip as rpm's increased.There are other issues I won't bore you with.The bottom line is the alt.s magnetic field acts sort of like a clutch on a kids go cart and once again you need to think long and hard about trying to outsmart the datsun engineers.They know.

Dan, My Z does the same thing. I'm putting in a new VR on Tuesday. If this solves the problem I'll let you know.

Thanks Ed i'd be glad to hear what happens.

Hey Dan, RU going to the Motorsports Z show May 5th? CU there.

Yep i wouldn't miss it. I will be taking my humble 240 up there although i'm not going to show it. I think that go z racer and i will try and drive up there for a day. If you would like to drive up there also i think it would be a laugh to get a train of Z's on the highway for the trip.

I have noticed the same thing with my 240Z. I am even running a '81 L28 and it does the same thing. When I asked around (at length) I found that this was a 240Z thingie. According to some old Z nuts I talked to in Illinois, the 240Z alternator is acutally not a alternator at all but rather a generator. Why the difference is slim, the faster it turns the more power it cranks out. I changed out my voltage regulator and same thing happens. [puzzled look] I suppose that it really is not a big deal since it is usually over 1000 RPM when driving anyway.

I put in a new battery and a new V.R. It still does the dimming thing below 1000 rpm.

Thats just what they do.The charge and discharge just about breaks even at less than 1000 rpm,s.I'm just glad you got yours repaired before any real damage occured and without injury!! Daniel