Hey all,

So i have an 87 iroc z 5.7tpi

Lately my voltemeter has been fluctuating, and my headlights have been dimming and getting brighter.

Lastnight i was driving it and the voltemeter dropped down to 8. It started idling quite poorly.

I popped the hood with it still running and with a chopstick, i pushed on the alternator plug to manipulate it.

As soon as i did that the headlights got brighter and the idle went up.

I pulled away and it went back to 8v on the meter and idled crappy.

MY QUESTION IS: what needs replacing?

 

Pull the plug out and look to see if it's the contacts on the plug or on the alternator.

 

Will do when i get off work.

I wonder if its the plug, because it looks like its seen better days. The only issue is the advance auto website pic of the plug looks different than mine...

Makes me wonder.

Anyway, i post when i get to the car later today!

 

Update:

Just got home, decided to replace the plug. Did so.

Car needed a jump start. When I did, the voltemeter jumped up to around 12.

As the car warmed up it gradually died down.

I was driving and it literally went down to 8.

I tried to roll up the windows and they stopped halfway. Car was still running.

Suddenly the needle jumped back up to 12 and my idle changed. I was able to roll them up.

What does this sound like?

Plug is ruled out.

 

I'd have alternator tested - almost any parts store will test for free in the car. I had a new alternator, that fluctuated voltage and dimmed lights, and turns out the new alternator was bad, and overcharging. New doesn't mean good, just means new.

 

Sounds like it needs a new alternator, or you can put new guts in it yourself.

 

hmm. Im guessing its the regulator.

i was essentially applying pressure on it when i was pushing the chopstick into the plug.

That tells me that the other components of the alt. work, I think.

I think ill pick up a new regulator.

 

Unless the voltmeter is bad, a non-charging alt shouldn't suddenly drop the volts to 8 or below and then back up again. Sounds more like battery terminals/cables/grounds, or old battery with crud in it moving around.

 

id blame the voltemeter if only it was malfunctioning.

I just dont think the whole alt is bad.
Its almost brand new (remanufactured)

The voltage regulator, which was the only part i was coming into contact with, through the plug, was making the headlights and all the stuff change when i applyed pressure on it.

Im leaning towards that

 

I'm having similar problems; most prevalent at night.

At about 35-40 mph, when the tach is between 5-10k, I can see the tach bouncing like a pendulum. Faster speeds, not so much. At red lights (car in drive but at a complete stop) the headlights can be seen flickering, and volt gauge drops to 8. Once going again, it fluctuates between 8-12. Last night was the second time this happened to me this week. After the first time, I removed and reinstalled the battery cables, tightened the alternator cables and sprayed electrical contact cleaner into the alternator female plugs. Didn't seem to make a difference.

I'm still waiting to hear from others if a faulty voltage regulator sounds like the culprit but for anyone interested in knowing the location of and how to replace the regulator, should it need to be done, I found a short video here: http://www.youtube.com/watch?v=T7V8E8YlNls

To rebuild a GM alternator, I found a good video here: http://www.youtube.com/watch?v=LdFA6...eature=related

 

For those having troubles, has anyone noticed a perfectly normal operating range when starting the car for the first time in the day? Since I've been having this problem, I noticed that today, when I first started the car and for the first few minutes, the gauge went right in the middle (where it used to be before this week). After a few minutes though, it began to creep back down again.

 

i have a similar issue i haven't been able to fix my problem is that it will run at proper voltage until you apply head lights or any kind of draw like that i have replaced the battery a few times through its warranty and the alt has been replaced 3 times through the warranty i put a new ground at the back of the block to the firewall and the pos and neg cables for the battery are both clean and in near new condition

 

i have the same issues with my 87 5.7. i just put a new alternator and all new battery cables in today along with a new 2 gauge head to fender ground. still no change same as before.

voltage at idle in drive with headlights on and foot on brakes drops below 11 then goes back up...if i throw the turn signals on forget it it gets so dim you think its gonna shut off. i checked all voltages sitting at home in driveway in drive lights on foot on brakes etc. voltage at batt and alt was 14.2 volts but it was making lights dim and idle surging

kinda stuck now...the voltages read fine on both my multimeters at batt and alt but the car idles really low and feels like its gonna die. stock voltmeter and aftermarket voltmeter in car show voltage dropping to around 10.

 

Check your starter motor. I had a 79 Malibu do the same thing. It could be that the positive line on the altinator bolt is loose and its bouncing around as you drive. It gets power and will make all those symptoms. I cant say im 100% sure thats the problem, but there is a very strong possibility and will save alot of money if it is. V8's vibrate like mad, and it will loosen the bolt on it.

 

ill check it when it stops raining up here in dirty jersey. thanks man. if its not that im gonna shelf the car and tear out the wiring harness. this cars been hacked by soo many different people it could be anything. im just trying to get the usual suspects down first.

 

I am going to double check my starter also need to figure out the prob since i was thinking of selling the car

 

Same prob here, but only when rear defrost is on at night and it's only the voltmeter (lights don't dim and idle is fine) New batt (720 cca), good voltage according to multimeter. Alternator is about 3 years old. One of the connections kept working loose on starter last year so i need to check that again. It'll be a few days before i can check into it, but i'll keep everyone updated.