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auvelas

240z electrical issue

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Im new to forum and new to the 240z. Recently purchased a 71 240z bone stock L24. Im upgrading the 60amp alternator and have followed the DIY. Seemed easy and straightforward. Tested alternator to ensure its working well. Tested battery also good.

I modified harness and eliminated old regulator and covered harness socket. L to 12v source via fusible link white wire and S to b/W (SWITCH 12V) with diode. Diode line faces alternator.
Everything good so far. Here is what happens.
 
Tested while running with volt meter battery and read 12.6 (not good)
I remove negative cable from battery and it reads 14.5(good) the alternator sounds different meaning regulator is put to work.
I connect negative cable back on and voltage drops back to 12.6
something happens with that battery ground.
I dont get it. Please help you Z experts.
 
 
 

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Did you buy a kit or did you just build the stuff from scratch? I bought the kit from MSA. They have just the regulator replacement adapter plug or you can get it with the 60 amp zx alternator. I got both the alternator and the regulator replacement adapter and it was truly "Plug-n-Play".

http://www.thezstore.com/page/TZS/CTGY/classic10b04

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8 hours ago, auvelas said:

Im new to forum and new to the 240z. Recently purchased a 71 240z bone stock L24. Im upgrading the 60amp alternator and have followed the DIY. Seemed easy and straightforward. Tested alternator to ensure its working well. Tested battery also good.

I modified harness and eliminated old regulator and covered harness socket. L to 12v source via fusible link white wire and S to b/W (SWITCH 12V) with diode. Diode line faces alternator.
Everything good so far. Here is what happens.
 
Tested while running with volt meter battery and read 12.6 (not good)
I remove negative cable from battery and it reads 14.5(good) the alternator sounds different meaning regulator is put to work.
I connect negative cable back on and voltage drops back to 12.6
something happens with that battery ground.
I dont get it. Please help you Z experts.
 
 
 

@Zed Head likes to poke fun at me about this, but I'm going with my standard line of posting. We need more details.

What DIY? There is more than one. Can you post a link to it?

Can you post quality photos of your wiring modifications, including the diode with polarity shown? 

Can you provide the part number of the diode you used? 

There is some issue with sensing battery voltage. The additional information may clear it up.

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Me?  I'm not a fun-poker.

Doesn't this just sound a like discharged battery, and taking measurements at low RPM, where the typical alternator is barely generating any current?

When he disconnects the battery the alternator doesn't have the battery load to deal with and the current draw drops.  If it wasn't at low RPM voltage would probably jump to 16 or 17.  There's no S circuit anymore with the battery disconnected.

auvelas, don't disconnect the battery while the engine is running.  It can damage your alternator.  Leave everything connected correctly, and take a voltage measurement at higher RPM.  Like the FSM says.  More details, like SteveJ says.

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I will get pictures by tonight. I will say i followed the MSA wiring but instead of the adapter i simply modified my harness by pulling out the wires needed and doing the same wiring. Guys, what i dont get is when everything is connected voltage is low and should be high 13 to 14 from alternator. I rev motor and alternator makes loud noise. Almost like belt is making noise but its not. It specific to alternator because when negative terminal is disconnected the noise goes aways and alternator sound normal and voltage range goes to 13/14. The battery and alternator tested and fully charged by the way.

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18 minutes ago, Zed Head said:

auvelas, don't disconnect the battery while the engine is running.  It can damage your alternator.  Leave everything connected correctly, and take a voltage measurement at higher RPM.  Like the FSM says.  More details, like SteveJ says.

 

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Attach is a picture of wires being used. The diode in place is 1n5406. If you notice how the line of diode faces alternator plug. Many sites show diodes with different #s and now i wonder if that is the problem. I know for certain this diode does stop current being i tested wiring with no diode and car continued running with ignition off. 

20171114_221608.jpg

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What about the jumpers needed at the connection for the voltage regulator?

Also, what do you mean by you followed the MSA wiring? They sell products, and I don't recall seeing tech tips on their site.

Edited by SteveJ

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Its basically the only 2 wires needing modification. Everything else was not needed and just wrapped. BAT and Earth was also straight forward.

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That is what i did from my first email requesting SOS. I just dont have pictures showing the connections to the b/w to w/b , Y to W.

I think i will do another diode with the common one most use 1n5402 and see wha happens.

 

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The best advice I can give you is to put all the wiring back to stock specs.

Then, at the 6-pin connector that normally plugs into the Voltage Regulator (VR), due the following....

Connect the white and yellow wires together.
Connect the black/white and white/black together using the diode. The stripe on the diode goes to the white/black wire.
Use an internally regulated 60 amp alternator (81' to 83' 280ZX and other similar units)

That's the best I can do for you at the moment.
Dave

Diode wiring diagram.jpg

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ALSO........
after you've done all the above. Run an 8 gauge power wire from the (B+) alternator output bolt to the Starter's battery cable bolt.
This will give you better, more efficient charging and minimize the higher amperage damage to the old 45 amp ammeter.

This will stop it from over heating, not damage the ammeter and you'll see less movement on the ammeter dial.  But you'll still have plenty of power to the fuse box. I had it this way on my 70' 240Z for 8 years with NO issues.

Also a great idea to increase the battery cables to no less than 4 gauge with new clean and tight terminals.
Pull the ground wire from the fender (below the battery-above the frame and across from the starter) and clean the metal surface and terminal and re-tighten snugly. That ground is from the alternator, dash and engine harness.
Make sure you have a good ground wire from the Battery's negative post to the firewall as well.

 

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I appreciate your input guys thank you. I have done all of what you recently suggested Dave

 I will circle back to original wiring and redo wires and diodes. Hopefully its my diode or bad ground somewhere. 

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