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Alternator not working


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ECU2015
New User

Aug 4, 2011, 2:57 PM

Post #1 of 6 (3045 views)
Alternator not working Sign In

I have a 1985 Nissan 720 2.4L with just over 179,000 miles. I paid $600 for the truck so I didn't expect the best thing ever. I bought the truck and it was running fine until one day, I went to drive the truck, and it wouldn't start. It just made a clicking noise so I stopped and went back later and got the same result. My first hunch was the battery had died, but I was unsure how because the lights have to be turned off by switch and the battery was replaced in 12/10. Went out the next day and jumped off the car and it cranked. Took the battery to be tested and it tested well and was charged. So my next guess was the alternator. Took it off, took it to Advanced Auto, and found out the alternator was good. So the battery is good, and the alternator. Pulled out the ohm meter and the batter was 12.5 idle which is good, cranked up the car and the volts kept falling instead of rising due to the alternator. Found out the previous owner had broken the alternator pigtail and restored with glue, so the plug could've just been loose. However, now the plug has been removed and I've been looking for a new plug. Unsuccessful. Found a way to restore the 2 pronged socket by using wire and female wire gauges. Yet, the alternator and battery are getting the same results. Could it possibly be the battery cables? This is a 1985 Nissan truck.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Aug 4, 2011, 3:35 PM

Post #2 of 6 (3031 views)
Re: Alternator not working Sign In

You do have a problem with the charging system but it's not the alternator. You're going to have to troubleshoot the rest of the circuit. Start with testing all your fuses and fusible links using a test light. Test for power at the main terminal of the alternator with the key OFF



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Aug 4, 2011, 3:44 PM

Post #3 of 6 (3029 views)
Re: Alternator not working Sign In

Keep looking for a good pigtail new or used and solder/splice in a good one properly. IDK - perhaps the patched pigtail has taken out the alternator.

FYI etc: 12.5v (you meant volts didn't you?) at idle is NG. Should show more like 14v or so with nothing on in particular.

Get a "Floating trickle charger" or an automatic shut off one that's stronger and keep battery charged up or you'll kill it. They hate running down too low or worse dead even if new.

IDK again but check out some major parts chain's websites and identify you alternator if nothing else. Does it list an internal or external voltage regulator for your exact one? No doubt the truck had choices in alternators from new depending on how it was intended to be used. That's my best guess for now,

T



ECU2015
New User

Aug 4, 2011, 5:40 PM

Post #4 of 6 (3020 views)
Re: Alternator not working Sign In

Thanks guys. Well I have read that without the car on, having the battery read at 12.5 is good, but once the car cranks, the alternator should kick in and it should ready 13.5-14.5v


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Aug 4, 2011, 6:01 PM

Post #5 of 6 (3011 views)
Re: Alternator not working Sign In

Yep, that's true.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Aug 4, 2011, 6:10 PM

Post #6 of 6 (3007 views)
Re: Alternator not working Sign In

Close enough for me. Normally the plain volt reading will dip if your meter is fast while cranking and not below about 11v or so. When the dip below like 9.5 with a quick crank that's about where I worry about either battery wasn't fully charged or is starter is working too hard or battery amps inadequate and should be questioned.

Have a silly power port/cig lighter digital voltmeter for 10 bucks and don't know how accurate but it's easy and small - handy to check out a vehicle quickly without a monster tool box full of stuff if on a road call. Gives me the idea anyway on the spot,

T







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