Electrical Gremlin

[KeysZ]

I have a 73 Z production 12/72, and owned it since new.  I am in the process of finishing the resto and have encountered a lighting issue.  With the key on the directionals work properly, front and rear.  The rear light has the upper and lower lights blinking at the same time.  When I turn on the marker lights, the directionals still work but the rear upper blinks slightly before the lower and all the marker lights dim in time with the blinker.  I have tried it with the hazard flasher with the same result.  I removed the bulbs one by one-no change. Checked the ground at each socket and all good.  Is this unique, or has anyone encountered this.

 

[SteveJ]

How old is the battery? Is the car running? If not, hook up a battery charger that has a 10A or 15A setting. Repeat and see if you get the same results.

[KeysZ]

Steve, the battery is one year old.  I tried it with a charger connected (15 amp) no change.  Also, no change with the headlights on or off.  There is no voltage at the marker lights when they are off and the blinker is on.  The blinkers seems to only have the issue when the marker lights have current.

[SteveJ]

Post a video on Youtube of what is going on and link it here. Some visual evidence may help.

[KeysZ]

Will do.  Do you think the flasher is suspect?  I will check the drain with an ammeter with the markers off and the battery charger connected. and again with the markers on.

[SteveJ]

I'm not sure what to think without more information.

[jpc3006]

KeysZ,

FYI, I also am the original owner of a 73 (1/73 build date) so I went and tested the turn signals as you described. The marker lights on my car also dim slightly when the directionals blink (when the parking lights or headlights are on). I probably would not have noticed this unless I was specifically looking for it and this is not surprising as the marker lights and the tail lights are on the same circuit. 

I could not detect any difference in the blinking of the tail light and the turn-signal/stop light. Since you are noticing this when you change the position of the combination switch, that is where I would focus my attention. 

Note that I have installed MSA's parking light upgrade harness so the current driving the lights is through a relay and not the combination switch so the behavior I see may be different than your car.

John

 

[KeysZ]

Thanks, John.

 

I have Dave's headlight relay harness-but not the parking light harness.  I checked the draw with an ammeter and noticed no big drain. I suspected a wiring issue between the turn signals and the markers-but the turn signals did not light the markers when they were off.  I thought it would work in both directions.  I am going to install a new, electronic flasher to see if that could be the problem. I reconditioned the combo switch and the turn signal switch, so the contacts are clean.  I have the incandescent bulbs, so LED's are not an issue-unless the LED dash lights are a problem.  I will check the dash light dimmer tomorrow. I will post the results. good or bad.

 

Glad to chat with an original owner.  I had the original engine rebuild by Datsun Spirit = Stage 3 and hope to get on the road soon.  I logged 102000 miles before I began this project.