240z electrical issue

[auvelas]

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.

 

 

 

[w3wilkes]

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

[SteveJ]

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.

[Zed Head]

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.

[auvelas]

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.

[Zed Head]

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.

 

[auvelas]

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. 

[SteveJ]

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 November 15, 2017 by SteveJ

[auvelas]

No tech tip. The wiring looked simple enough to do my own. The picture provided is the T shaped plug for the SL. 

[SteveJ]

Okay, but there is more to it than just that plug. What else did you do?

[auvelas]

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

[SteveJ]

There are wires on the engine harness connection for the voltage regulator that need to be jumpered out. Please read this and tell us if you modified your wiring accordingly. http://www.zhome.com/ZCMnL/tech/280Alt.html

 

 

Edited November 15, 2017 by SteveJ