electrical drain?

[zdude1967]

I had the 74-260z out the other day at night. Headlights as well as radio and heater fan on. I had to make a turn and put the blinker on and the headlights and dash lights started dimming with each blink of the turn signal, the amp gauge also dropped with every blink and the tach gauge also dropped with every blink. Is this normal or do I have an issue with something. I know the electrical system in these cars does not produce much surplus power so is this normal. 

 

 

[Zed Head]

Not normal.  Could be a weak battery or alternator or both.  Best thing to do is take some measurements.

[SteveJ]

To add to what @Zed Headsaid, start with page EE-19 in the factory service manual. As the FSM says, make sure you have a fully charged battery before you test. Test the alternator and regulator.

Added: Oh, I forgot to mention, make sure you have the proper tension on the alternator belt.

Edited January 8, 2021 by SteveJ

[dutchzcarguy]

Your blinkers could be rusted badly..  they look fine but the rear part can be very bad ( the ones in the front fender) making a sort of short circuit that will dim all your lights.. just a guess, but seen with other cars..

[texasz]

To add to what has been said already, rust/corrosion will cause resistance in the circuit which can result in the issue you described.  Start with the easy test, drop in a shop/garage or place like Batteries Plus or auto parts store and have the battery/alternator tested.  If those both test to be in good condition start chasing down resistance in the circuit by cleaning up connections...start with the ones most likely to be bad like the ones on the outside of the car like @dutchzcarguy mentioned.  There can also be corrosion on/in the fuse box as well as the switches on the steering column.  When going through all of these connections and cleaning them make sure that there is good contact and that they are tight also.

[Dave WM]

also make sure you have GOOD battery cables, Stock and in good condition FUSE LINKS, make sure spade connectors are in good condition where every you find them. Good Grounds are essential too. Its a process you are fighting nearly 1/2 century of possible corrosion that will limit current flow.

[zdude1967]

Thanks everyone- I will get on this tomorrow and begin by getting the alternator and battery checked. I had fixed bad turn signals on this car a few years back, replaced the hazard switch the combo switch, flasher and the signals worked however a few months ago the passenger side stopped working maybe this is part of the current issue perhaps due to corrosion ?

[zdude1967]

UPDATE - so the battery and alternator were checked both were fine. The other day I installed a resistor on my tach connection- reason being that I installed the crane xr-3000 awhile back and my tach then became bouncy and erratic. So it fixed the tach issue PLUS...HERE IT COMES also the tach bouncing when the turn signal was on. Seems the crane upgrade can jack up quite a few things. Well anyway this solved two issues both the tach erratic behavior due to the crane install plus my electrical issue when the turn-signal is on. Like a buy one get one free...

[Zed Head]

On 1/7/2021 at 7:54 PM, zdude1967 said:

the headlights and dash lights started dimming with each blink of the turn signal, the amp gauge also dropped with every blink 

How about the other stuff?  Might also be that your idle speed is just too low.  The alternator/crank pulley ratios are not quite right on the Z's.  If they'd just made the alt spin a little faster, many problems like this wouldn't be around.

An extra 100 RPM of idle speed can make a difference.

[heyitsrama]

@zdude1967 I had a 260z tachometer in my 260z that would also do that to me, it would often wave, or bounce around depending on the electrical load. Or the engine RPM I had a 280z tach o that I finally got working and it’s a champ. The internal circuit board on the 260z seems to be more prone to this, than the 280z circuit. I have a thread on this a while back when I was trying to figure out why nothing was working properly (spoiler the transistor ignition unit was not OEM and was not keeping a clean circuit to the tach)  
 

You might want to find a 280z taco if your waving issue persists. Or at least tape a paper hand on the needle so you can wave back to it when using the blinkers. 😛