I think my alternator is going bad, but I need a second opinion. Here are the simptoms
1. When the car is off battery voltage is 12.5V
2. At idle (700 RPM, no load) voltage is ~14V
3. At idle with full load (heater on, lights on, defogger on) voltage drops to ~12.5V
From my experience with my other car, this indicates a bad alternator, since it has to always keep the voltage above 13V no matter what. If it does not, the battery is drained at idle. Am I right?
Can it be anything else? The voltage is fine when I cruise. Can it be belt slipping? I don't want to adjust my idle to fix that. Can anyone run his car at idle with full load (item 3) and check the battery voltage?
Thanks
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94 3000GT VR4 (upgraded)
"Your 1994 Mitsubishi 3000GT VR-4 is one of 1650. There are 57 other cars that were made with both the same interior and exterior color. Exactly Identical - 8"
I think my alternator is going bad, but I need a second opinion. Here are the simptoms
1. When the car is off battery voltage is 12.5V
2. At idle (700 RPM, no load) voltage is ~14V
3. At idle with full load (heater on, lights on, defogger on) voltage drops to ~12.5V
From my experience with my other car, this indicates a bad alternator, since it has to always keep the voltage above 13V no matter what. If it does not, the battery is drained at idle. Am I right?
Can it be anything else? The voltage is fine when I cruise. Can it be belt slipping? I don't want to adjust my idle to fix that. Can anyone run his car at idle with full load (item 3) and check the battery voltage?
Thanks
Those aren't symptoms of a failing alternator. You're battery won't start draining until you are under 12V and idling even at full load doesn't even last that long. New these cars had either 90A alt's or 110A alt's. This is just sufficient enough so you shouldn't really expect over 13V at idle under full load. Now when you're getting 12.5V with only a few accessories and you're above 2000 rpm's you may have an issue.
It is normal; with all those loads the alternator can not produce enough voltage and current to overcome the demand at idle. Roughly 700RPM is about 2100 rotor RPM. Stock Alternators produce it's full output at about 6000 rotor RPM and that is about 2000RPM in your car.
so a stock alternator at 2000rpm(engine) should produce 14.3v? or 13.6? or something else...
i have squealling belts and low readings from my turbo timer volt gauge. i adjusted for the belts, but they are starting to come back. and i still have what i consider "bad" volatage. and a tester revealed 12v at idle 11.x with the load switch on
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1992 silver VR-4
K&N // Turbo XS MBC // HKS SSQV open// Dejon Tool Ypipe // MAFT-T + 3" MAS// Southbend DXD// Accel coil packs + 8mm wires// Champion copper plugs .39 gap// Hotwired FP// Vac reduc no egr // Panasonic DVD system 7" screen// Alpine Type S // Clarion 50Wx4 // Type S 10" subs// 1000w bridged mono block
SHE'S BACK!!-down again w/spun bearing.
of ALL the ISH!!! they can't make a bearing that don't spin
Reppin tha 401 till i can get tha hell out!!
Remember those Kool Aid commercials? Where that big talking bowl of punch, he would come crashing through your f**king wall in your living room... You wouldnt even know, just "OH YEAH!" and the little kids would be so excited, and then they would drink out of him after debris fell in his open dumb head. He would pour himself, "OH YEAH!". Him and his crazy tights, I dont like that, I dont like it when juice wears tights. Fuck drinking out of him, I'd be like "no no no, you fix that wall before my dad gets home from work. Hes gonna beat me with a belt, hes not gonna believe a talking bowl of fruit punch came in here
Thanks. I'll keep my eye on it though. I remember reading in Haynes and couple of places online that it should always stay above 13V, but maybe this does not apply to our alternators.
If you haven't upgraded your charging system wiring do so with 0, 2 or 4 guage wire. These are the wires from alt to bat +, bat - to ground, starter. Also a ground kit will help with electic flow.
@flux
You definitely don't want to be going under 12v although that's not a fair test when you put full load at idle. Your symptoms are not a sure sign that you're alternator is bad. Like you said it could be your belt problem. If the belts aren't revving as fast as normal that's less energy produced. Also if you haven't done my above suggestion try that it will help.
i just finished putting together a ground kit, i need to make one more from the alt ground tho. i think i will do a 4 gauge power wire too... thanx for the idea.
this morning for the first time that i remember my voltage was at 13.8 so i'm really starting to think i have a belt problem. they seemed pretty loose when they were squealing so i went as tight as possible before they started to squeal again... every now and then they get alittle whiny tho... i also found (my logger) that my tach is off about 150 short of what it reads.
so now i have to mess with the BISS screw. shes just acting wierd lately. i'm getting quicker spoolup since i did the wire kit/ belt adjustment but my gas/mph went down from avg of 350 on the tank to 280.... i gotta do some more logs and check my tps curve. i'm kinda baffled. i want to figure out whats goin on before i install my MBC and do the vac reduc.
damn thos throttle body/ elbows go back on tough! xcuse the rambling i'm just tryin to show the bigger picture
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signs of bad alternator?
Re: signs of bad alternator?
