SR Alternator- 4 volt output - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

KeiStarr · 07-13-2009, 12:52 AM

I recently did my sr swap, everything is working great except the alternator power output. I started to drive the car after the swap and noticed the power was spiking. Once I got back to the garage I went to check the alternator and it was pushing out only 4-5 volts of power. My first guess was maybe the alternator was going bad so I took it out and got it check along with the battery, both passed testing. I swapped the alternator with another just for good measure, and used another lower harness (both off of a good running car). I'm pretty sure everything is grounded as well.
Any suggestions to my situation? Thank you in advance.

*fliprayzin240sx* · 07-13-2009, 01:13 AM

So you changed the alt and same thing? Make sure everything is plugged in properly and the ground wire isnt touching the housing (plastic spacer on it has a tendency to crap out).

KeiStarr · 07-13-2009, 01:51 AM

Quote:

Originally Posted by fliprayzin240sx

So you changed the alt and same thing? Make sure everything is plugged in properly and the ground wire isnt touching the housing (plastic spacer on it has a tendency to crap out).

Yeah, changed the alternator and still had the problem. I'll check out that spacer your talking about.

FRoSt415 · 07-13-2009, 07:00 AM

Check your connectors then to where i grounds out on the chasis.

clark · 07-13-2009, 07:06 AM

yeah i agree with tehse guys, sand/file down the contacts on the alternator and the low gauge wires and ground points on the manifold and chassis.

i had alternator issues too and it was because of a loose connection on the positive terminal of the alternator.

the SR alternator on mine had a separator that just disintegrated, so i used a plastic washer and all was well after that.

KeiStarr · 07-13-2009, 01:34 PM

I'll get to that washer after work today, I also forgot to mention that my car does shut off when I remove the positive battery cable. Does this follow along with the rules of the your guys' suggestions?

*fliprayzin240sx* · 07-13-2009, 03:13 PM

That means your alternator sucks and your car is running off your battery. If you unplug you're battery with the car running, it should run off the alternator. The job of the battery when the car is running is to re-charge itself up, not run the car.

teamsprock · 07-13-2009, 03:18 PM

You really don't want to disconnect the positive side like that on modern cars. But check the clip on the side. The alternator only puts out the voltage/amperage it needs to keep the battery charged and it uses a wire on that clip to tell it what to produce. Its been a while since I worked on an alternator but I can look for it if you need it. One wire sends the signal to the cluster that is meant by the same voltage coming from the ignition switch and this is what controls the battery light. The other wire is the exciter/load signal wire. You can also undo that clip and see what the voltage output is. Some alternators require that it get a signal from this on start up to tell the alternator to work so I'd unplug it after you start the car. Then check as output should raise if this wire is the problem. You can rewire this really easy if the factory wire has gone bad.

Also if those wires are clean and have good contacts the other usual cause for low voltage is a bad diode. But since you switched alternators I would doubt that is your problem.

07-13-2009, 12:52 AM	#1
KeiStarr Join Date: Jul 2008 Location: Las Vegas Posts: 31 Trader Rating: (2) Feedback Score: 2 reviews	SR Alternator- 4 volt output I recently did my sr swap, everything is working great except the alternator power output. I started to drive the car after the swap and noticed the power was spiking. Once I got back to the garage I went to check the alternator and it was pushing out only 4-5 volts of power. My first guess was maybe the alternator was going bad so I took it out and got it check along with the battery, both passed testing. I swapped the alternator with another just for good measure, and used another lower harness (both off of a good running car). I'm pretty sure everything is grounded as well. Any suggestions to my situation? Thank you in advance.

07-13-2009, 01:13 AM	#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	So you changed the alt and same thing? Make sure everything is plugged in properly and the ground wire isnt touching the housing (plastic spacer on it has a tendency to crap out). __________________ If you think Zilvia has too many assholes... CLICK HERE!!!

07-13-2009, 03:13 PM	#7
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 means your alternator sucks and your car is running off your battery. If you unplug you're battery with the car running, it should run off the alternator. The job of the battery when the car is running is to re-charge itself up, not run the car. __________________ If you think Zilvia has too many assholes... CLICK HERE!!!

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07-13-2009, 07:00 AM	#4
FRoSt415 Zilvia Junkie Join Date: Dec 2006 Location: san francisco Age: 34 Posts: 305 Trader Rating: (0) Feedback Score: 0 reviews	Check your connectors then to where i grounds out on the chasis.

07-13-2009, 07:06 AM	#5
clark Zilvia FREAK! Join Date: Mar 2008 Location: new york Posts: 1,035 Trader Rating: (1) Feedback Score: 1 reviews	yeah i agree with tehse guys, sand/file down the contacts on the alternator and the low gauge wires and ground points on the manifold and chassis. i had alternator issues too and it was because of a loose connection on the positive terminal of the alternator. the SR alternator on mine had a separator that just disintegrated, so i used a plastic washer and all was well after that.

07-13-2009, 01:34 PM	#6
KeiStarr Join Date: Jul 2008 Location: Las Vegas Posts: 31 Trader Rating: (2) Feedback Score: 2 reviews	I'll get to that washer after work today, I also forgot to mention that my car does shut off when I remove the positive battery cable. Does this follow along with the rules of the your guys' suggestions?

07-13-2009, 03:18 PM	#8
teamsprock Zilvia Addict Join Date: Sep 2006 Location: Billings Age: 38 Posts: 636 Trader Rating: (8) Feedback Score: 8 reviews	You really don't want to disconnect the positive side like that on modern cars. But check the clip on the side. The alternator only puts out the voltage/amperage it needs to keep the battery charged and it uses a wire on that clip to tell it what to produce. Its been a while since I worked on an alternator but I can look for it if you need it. One wire sends the signal to the cluster that is meant by the same voltage coming from the ignition switch and this is what controls the battery light. The other wire is the exciter/load signal wire. You can also undo that clip and see what the voltage output is. Some alternators require that it get a signal from this on start up to tell the alternator to work so I'd unplug it after you start the car. Then check as output should raise if this wire is the problem. You can rewire this really easy if the factory wire has gone bad. Also if those wires are clean and have good contacts the other usual cause for low voltage is a bad diode. But since you switched alternators I would doubt that is your problem.