Sr20det Alternator Question - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Smith28 · 10-18-2012, 08:45 PM

I have a 1993 240sx that was swapped with a sr20det Blacktop, once i finished the harness wires i noticed that my battery would not hold a charge and my idle was jumping anywhere from 400-1500 rpms. I got frustrated and tore the harness back apart and while testing wires i noticed that my Red (ECU Backup power) wire had continuity to ground.
I traced it back to the passenger side fusebox in the engine bay and noticed that all of my white wires under the fusebox that included the ALT power wire which has like a 5-way splice on it to run things inside the fusebox off of the positive battery cable. I started disconnecting fuses to try to narrow down the possibilities of which wire was touching ground and found out the the B+ wire from the alternator was grounded. I took off the wire and tested the B+ post to ground and sure enough i had continuity to ground.
Long story short my B+ post on my alternator has continuity to the alternator casing. Does this mean my alternator is fried or can there be a wiring issue? Any help is appreciated, thanks

*fliprayzin240sx* · 10-19-2012, 04:23 PM

Which wire is the B+ wire you're talking about? You talking about the ground wire thats hooked up to the small 10mm screw?

Smith28 · 10-19-2012, 06:14 PM

I'm referring to the White wire that runs from the stud on the alternator to the splice in the fusebox and out through the the 75A and then to the red connector on the positive clamp for the battery. But I'm not for sure if its a 10mm or 12mm nut that holds the wire against the plastic insulator on the stud.
This leads me to believe that its the B+ or battery post for the voltage which shouldn't have continuity to ground, but in my case it does.

*fliprayzin240sx* · 10-20-2012, 05:36 PM

That shouldnt be grounding out. Question is, when you're checking it, are you checking the alternator stud with the line off it or with the line bolted on it? If its just the stud on its own and its grounding out, is the plastic insulation cup around it still there? I'd take the alternator out and get it tested just to see.

How much voltage are you seeing at the battery when the car is running?

Smith28 · 10-22-2012, 06:57 AM

You sir are correct and after taking it to 3 Advance auto stores the third and final one is the only store that could tell me that it was internally shorted and was grounding itself out...Ive replaced the alternator with one from a 1993 Ka24de and it works perfect, charging at 14.2v at idle... Thanks for the replys

10-18-2012, 08:45 PM	#1
Smith28 Join Date: Oct 2012 Location: Metropolis IL. Posts: 3 Trader Rating: (0) Feedback Score: 0 reviews	Sr20det Alternator Question I have a 1993 240sx that was swapped with a sr20det Blacktop, once i finished the harness wires i noticed that my battery would not hold a charge and my idle was jumping anywhere from 400-1500 rpms. I got frustrated and tore the harness back apart and while testing wires i noticed that my Red (ECU Backup power) wire had continuity to ground. I traced it back to the passenger side fusebox in the engine bay and noticed that all of my white wires under the fusebox that included the ALT power wire which has like a 5-way splice on it to run things inside the fusebox off of the positive battery cable. I started disconnecting fuses to try to narrow down the possibilities of which wire was touching ground and found out the the B+ wire from the alternator was grounded. I took off the wire and tested the B+ post to ground and sure enough i had continuity to ground. Long story short my B+ post on my alternator has continuity to the alternator casing. Does this mean my alternator is fried or can there be a wiring issue? Any help is appreciated, thanks

10-19-2012, 04:23 PM	#2
fliprayzin240sx Man w/ CTSV & a Car Seat Join Date: Aug 2002 Location: Tampa Posts: 17,998 Trader Rating: (19) Rides Gallery: fliprayzin240sx Feedback Score: 19 reviews	Which wire is the B+ wire you're talking about? You talking about the ground wire thats hooked up to the small 10mm screw? __________________ If you think Zilvia has too many assholes... CLICK HERE!!!

10-20-2012, 05:36 PM	#4
fliprayzin240sx Man w/ CTSV & a Car Seat Join Date: Aug 2002 Location: Tampa Posts: 17,998 Trader Rating: (19) Rides Gallery: fliprayzin240sx Feedback Score: 19 reviews	That shouldnt be grounding out. Question is, when you're checking it, are you checking the alternator stud with the line off it or with the line bolted on it? If its just the stud on its own and its grounding out, is the plastic insulation cup around it still there? I'd take the alternator out and get it tested just to see. How much voltage are you seeing at the battery when the car is running? __________________ If you think Zilvia has too many assholes... CLICK HERE!!!

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10-19-2012, 06:14 PM	#3
Smith28 Join Date: Oct 2012 Location: Metropolis IL. Posts: 3 Trader Rating: (0) Feedback Score: 0 reviews	I'm referring to the White wire that runs from the stud on the alternator to the splice in the fusebox and out through the the 75A and then to the red connector on the positive clamp for the battery. But I'm not for sure if its a 10mm or 12mm nut that holds the wire against the plastic insulator on the stud. This leads me to believe that its the B+ or battery post for the voltage which shouldn't have continuity to ground, but in my case it does.

10-22-2012, 06:57 AM	#5
Smith28 Join Date: Oct 2012 Location: Metropolis IL. Posts: 3 Trader Rating: (0) Feedback Score: 0 reviews	You sir are correct and after taking it to 3 Advance auto stores the third and final one is the only store that could tell me that it was internally shorted and was grounding itself out...Ive replaced the alternator with one from a 1993 Ka24de and it works perfect, charging at 14.2v at idle... Thanks for the replys