Electrical Gremlins - Tach and Turn Signal Indicator Lights

[pledgekincaid]

In the process of finishing up my manual swap and noticed one problem and apparently created another or two.

 

Firstly, I have a 75 280z. I am running stock everything as far as equipment goes. I have done a fusible link - distribution block change.

 

The problem I identified first was a lazy tach. Thinking this was a tach issue and not signal related I pulled the unit and replaced it with a spare. I still have a lazy tach and will be running a new line from the coil (-) to the tach using the existing in-line resistor to hopefully eliminate the issue. If there is an alternative solution to this please let me know.

 

 The tach replacement appears to have created my new and more frustrating issue. Now, my turn signal lamps do not illuminate as part of the tach. I swapped harnesses back to the original and the lamps still fail to light. Both front and rear signals still light on the car, though it does appear my right side flashes noticeably slower than the left. 

 

They do not light with the hazard switch activated. My hazard switch also no longer illuminates the right side lamps either front or rear. I hear the relay engaging. 

 

I hate chasing gremlins and would would love some guidance from the Z elders. I’m lost right now and don’t see where the issue for the indicator lights would be.

[NewZed]

22 minutes ago, pledgekincaid said:

The problem I identified first was a lazy tach.

 

Now, my turn signal lamps do not illuminate as part of the tach. I swapped harnesses back to the original and the lamps still fail to light.

 

What does "lazy" mean, in tach terms?  Is the ignition system factory stock?

 

Do the lights flash when you turn the emergency flashers on?  Have you checked the fuse?  Does the flasher unit make noise?

 

 

 

[pledgekincaid]

Lazy - tach rises with rpm but about as fast as your thermometer rises. So very VERY slow. It does not fall and despite how far I rev the engine it does not climb any faster.

 

ignition system is factory stock, no modifications in the electrical between solid blue off of the coil and plug on the back of the tach.

 

the tach indicators do not flash with either signal or hazard.

 

I have checked the fuses and had one blown on the 4th down on left. I replaced it with my cigarette lighter fuse temporarily although my fuse cover does not match the one you have shown so I have no idea which is actually which; I’ll have to get a photo of that in a couple hours.

 

the flasher unit does make noise when the signal switch is activated L or R, and the front and rear lamps work. Just not those lights for the tach indicators.

Edited April 24, 2019 by pledgekincaid

[NewZed]

Does it match RPM?  Could be a sign of a failing ignition module.

 

If the flasher makes noise then it must be getting voltage.  Current flow heats and cools the mechanism.  Always possible that the bulbs are burned out. 

 

Also, check the grounds.  Can't remember if the tach signal lights have their own ground wire from the socket or if they ground through the socket to the tach body.  Who knows, poor ground might also be the problem with the tach needle.  The ground circuit is often overlooked.  I've also found that the bulbs and sockets can be pretty touchy.  They have to be just right and are easily knocked loose.  Once you get in there sometimes the problems just grow.

 

I got the fuse cover picture from the 75 FSM.  You might have a more 76 like system.  75 had a lot of firsts, and new changes.

Here's 76.

 

 

[pledgekincaid]

That’s the cover I have. I know it was a late build car, could also be a donor.

 

i know the bulbs are good. Dash illuminates so I pulled those bulbs to swap.

 

The tach does not match the RPM. No where close. I will go through and clear up the grounds to make sure I don’t have issues there. 

[pledgekincaid]

So I ran a new signal wire from the coil (-) and relocated the resistor, tach still not doing what it should. I’m thinking the tach(s) are dying so I’ll be going the speed hut route I think. Any other insights before I spend a bunch of money is always appreciated.

 

I still need to check the relays and flashers but...

 

As for the hazard lights and indicators on the tach I will be, very likely, living with it for now and requiring the car in the fall.

Edited April 24, 2019 by pledgekincaid

[NewZed]

Here's two thoughts -

 

1. Check voltage at the coil.  Maybe your voltage regulator is going bad and "over-volting" things.  I don't know how a tach would react to that but it's a possibility.

 

2.  Spend $25 for a GM HEI module and wire it in quick and dirty.  It might actually make things worse, sometimes they cause their own tach problems, but it might tell you something.  Always good to have a backup ignition module anyway, the 40+ year old modules die on a regular basis.

 

Two cheap checks, compared to new gauges.  Good luck.

 

 

[pledgekincaid]

On the coil I should be reading my +12 across the terminals, correct? I see no reason to expect something different but want to be certain.

 

Ill pick up a new HEI and wire it up, maybe that’ll make it work.

 

This is all a labor of love so I don’t mind the work, I have plans for a turbo, full gauge replacement and a litany of other items, just want to get it to drive around the block before I tear into it again lol