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#1
11-05-2011, 01:25 PM
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Testing Alternator while in the car.
How do you test the alternator while the car is running? I am not sure where to put the multimeter leads? My car had to be towed home today, and I suspect the alternator and or battery. I'd like to try to test the alternator before removing it.
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1992 LSL ebony pearl 170k - Thank you Ron Mummert Reading Box of Wine Car ----------------------------------- 1992 SVX LSL 5-Speed Sold at 180K 2019 1995 SVX Lsi Polo Sold at 118K 2007 
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#2
11-05-2011, 02:04 PM
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Re: Testing Alternator while in the car.
Just put them on the battery posts. I forget what the output spec is, but you should be seeing 13V or more.
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Chris 92 Ebony Mica LS-L "A Rolling Restoration": 223,250 KM - Sleeping 2007 STi 6MT, Stance GR+ coilovers, PWR Rad, JDM hood badge, svxfiles 6000K HIDs, JDM Clear Corners, $15/15 min mod, $20/20 min mod, Energy Swaybar Bushings, Hella Supertones horns, Gold STi BBS rims, Group A lightweight crank pulley, A/C system removed, Custom header-back exhaust, Hybrid carbon/metal rear sway bar, restored headlights with CCFL halos 2008 Subaru Legacy Spec B - Diamond Grey Metallic - Sold 2020 Ram 1500 Longhorn - Red Pearl
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#3
11-05-2011, 02:20 PM
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Re: Testing Alternator while in the car.
SIMPLE TEST
Connect the POS and NEG leads of the multimeter to the POS and NEG battery terminals. Set the meter to DC voltage. On a fully-charged battery, you should read about 12.7V with the car off. Start the car and the voltage should go up at least 1V above that. this indicates the alternator is charging. Now load the system by turning on the lights and blower motor. The readings should initially dip and rebound. This indicates the alternator is handling the load. If the readings drop and not rebound, or slowly continue to drop, your alternator is having a problem with charging. The best way is to have it properly load-tested off of the car. .
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. Subaru Ambassador 1996 Polo Green LSi #216..138,100 miles...SOLD JFICX8659TH100216.....Date of Manufacture: November 16, 1995..... Fuji Heavy Industries..Ōta North Plant....Ōta City,. Gunma Prefecture, Japan In-Service Date: January 2, 1997 "The Pristine Green Polo Machine” First Polo Green on the Network First Clear front turn signals, JDM Alcyone hood emblem, rear panel, and BOXER engine cover on the Network (US) (2000) First 5000K HID factory fog lights (2007) First SVX JDM BBS wheels on a USDM SVX (2013) HID lighting (5000K) for headlight and H3 fog lights, PIAA SuperExtreme 120W high beams, rebuilt EG33 longblock, Cometic head gaskets, Phase II flexplate, AMR aluminum radiator with custom silicone hoses, 160A high-output alternator in aluminum-ceramic coated case, new design alternator wiring upgrade v.4, rare factory headlight protectors, refinished JDM BBS mesh aluminum wheels and custom, polished billet aluminum new hex center caps, LED grille mod, R1 Concepts high-carbon cryo slotted rotors, Akebono ceramic pads, Goodridge S/S braided brake lines, Smallcar Stage 1 shift kit, ThermalTech aluminum/ceramic-coated valve covers, Energy Suspension urethane front & rear swaybar bushings, Bontrager22 rear swaybar with QS Components Chromoly Teflon/Kevlar endlinks, "$15.00/5 minute" suspension mod. Hella Supertone horns, Custom stainless steel exhaust system with 2" headpipes, Magnaflow cats, AeroTurbine AR25 resonator /AWD "Bullet" muffler. R.I.P. 2010 Subaru Outback Limited 2.5 CVT...338,000 miles. Totaled by a 1,300 lb. COW March 4, 2016  2014 Hyundai Avante Limited ...178,000 miles. Actually quieter and smoother than the Outback  2007 Mazda Miata MX-5 PRHT...102,000 miles. Plenty of parts, service and windshields.  4th Registered Network member —2/21/2001 My NEW locker..I...My Email..I..Wikipedia/SVX . .
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#4
11-05-2011, 04:10 PM
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Re: Testing Alternator while in the car.
The battery is completely dead, it won't start with out a jump. Will it make a difference in testing if the battery is dead to begin with?
__________________
1992 LSL ebony pearl 170k - Thank you Ron Mummert Reading Box of Wine Car ----------------------------------- 1992 SVX LSL 5-Speed Sold at 180K 2019 1995 SVX Lsi Polo Sold at 118K 2007
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#5
11-05-2011, 06:48 PM
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Re: Testing Alternator while in the car.
It's best to have a fully charged battery with a battery charger.
Many people believe it's not good for the alternator to completely charge a dead battery.
__________________
Dave - 03 Baja - 92 SVX - 86 Brat - 08 OB 3.0
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#6
11-06-2011, 01:19 PM
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Re: Testing Alternator while in the car.
Thanks everyone. The alternator turned out to be okay, just too much corrosion on the negative battery terminal I think.
 I'm seeing 14v when the engine is idling.
__________________
1992 LSL ebony pearl 170k - Thank you Ron Mummert Reading Box of Wine Car ----------------------------------- 1992 SVX LSL 5-Speed Sold at 180K 2019 1995 SVX Lsi Polo Sold at 118K 2007
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#7
11-06-2011, 03:43 PM
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Re: Testing Alternator while in the car.
Quote:
For the SVX folks that are pretty aware about all the "why's", we have a variety of ways to determine exactly what the problem is even if we can't catch it "in the act" Keith 
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