I did install a separate fuse block next to the battery with 6 circuits. all of my aftermarket stuff comes from that fuse block. including the fan, fan controller, msd , and fog lights. everything in the cab runs off of the interior fuse block.

2 minutes ago, kully 560 said:

I did install a separate fuse block next to the battery with 6 circuits. all of my aftermarket stuff comes from that fuse block. including the fan, fan controller, msd , and fog lights. everything in the cab runs off of the interior fuse block.

the turn signals effect the tach also when the fan is not running, the tach bounces with the turn signal.

Just now, kully 560 said:

the turn signals effect the tach also when the fan is not running, the tach bounces with the turn signal.

let me see if the resistors have any effect tomorrow when they get here that should give me better in site. maybe that 2.2k ohm resistor in the wiring harness has some effect. I did bypass it with the direct wiring from the tach to the msd. my wiring is clean, as being electrician for 40 years, nothing is hacked but maybe I did miss something, we are never too old to learn something new. thanks

 I did find the problem today with the tach bouncing. I removed the cec electronic flasher for the turn signals and the hazard lights and no more bouncing of the tach with the turn signals and hazard lights. I did reinstall the oem niles flashers back in.  now I wired the msd 6a tach output directly to the tach and it does work fine. except when the cooling fan comes on it does drop at idle about 400 rpms momentarily. I then wired back in the v-booster and had to use 3-100k ohm resistor in parallel so I would get 33.3 ohms total between the v-booster tach output and the tach input, and everything still works great but now when the cooling fan does come on the rpms only drop about 200 rpms momentarily. making headway!!!!

thanks Zed Head for the help!!! I did take your suggestion today. I used the blue wire at the coil and with the early 74 ingition module removed. I had no continuity from the blue wire to the signal wire at the tach. I did try wiring direct again from the msd 6a tach output to the back of the tach and it works great. now when I did try that before, I was using the fan override switch in the cab to turn the fan on and the tach would drop, but I never let the engine warm up. [ too much load] now when the engine is cold it will idle at about 650 rpms and when fully warm up it will idle about 850 -900 rms. so with the lower rpms it looks like the alternator was not putting out enough. I am still using the stock charging system with a 50amp alternator, and also using the external voltage regulator. but I still can't use the electronic flasher, could be with some 90% led bulbs, but that is no big deal. thank you very much again for your help. you are a great forum member. kully

Funny, I forgot completely about the typical low output alternator problem.  I've never heard of it affecting tachometer operation though.  Maybe the combination of parts causes it.

You can get 60 amp external regulator alternators.  I think that the 280Z's all had them, until 1978 when they went to the internal system.  Might give a little bit more current/voltage at low PRM.  

Thanks for the compliment.  I appreciate a good puzzle.

yes, this also through me for curve ball. I think the spall electric fan was just too much current draw at the low rpms. I will look into the bigger alternator and see if rock auto lists the 60amp version! thanks

Just looking at the thread. Does the fan have a separate relay with the 12v source going back to he battery?

@SteveJ want to chime in.

Edited April 4, 20231 yr by Yarb

2 hours ago, kully 560 said:

yes, this also through me for curve ball. I think the spall electric fan was just too much current draw at the low rpms. I will look into the bigger alternator and see if rock auto lists the 60amp version! thanks

Well, since you're not concerned about stock...

 

hi Yarb, the fan does have a 30amp relay feed directly from the battery! and thanks Steve, for the video on the internal regulated alternator install. I did replace the alternator about 2 years ago with a 40amp version, but that was all that was available at that time with the pandemic. I did order it at Rock Auto after I read Zed Heads reply back this afternoon about the 280z 60amp alternator. it was the last one in stock, so I jumped on it. I did watch the entire video and saw he has a voltmeter in the car, but my early 260z still has the amp meter. I would have to look into that down the road if the amp meter gauge would need to be changed with a 280z voltmeter gauge. I do believe I would need the voltmeter gauge to complete the upgrade. but for $23.00 right now for the 60amp alternator it is not a big loss if and when I do decide to make the change down the road. thank you.

If said you saw a voltmeter in that video I linked, you need to go look again. I never installed a voltmeter in my car.

hi Steve, when he started the car, he had a little voltmeter in there that was reading 14.2-14.4 volts. did you install the upgrade alternator in your z and left the ammeter?