1986 Pontiac Firebird Charging System

Tiny
LIGHTHORSEOZZY1
  • MEMBER
  • 1986 PONTIAC FIREBIRD
Electrical problem
1986 Pontiac Firebird 6 cyl Two Wheel Drive Automatic

The problem I am having as been on going for some time now. I have replaced Battery and Alternator together so many times, I am going nuts. I have a charging gauge in the dash, which is factory equipment, shows the system at around 13.0. When I turn on the lights, the gauge will drop and not come back up to 13.0, even when idling or driving down the road. As time passes on, the gauge will slowly go down, where I eventually have to start changing Battery and Alternator, then it will return back to 13.0. Could cables going to block or to starter, cause this to happen or am I over looking something all together? Battery and Alternator, when bought, are for this year and motor size of this car. Please help if you can. Thanks. Ozzy
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Tuesday, November 18th, 2008 AT 4:29 PM

9 Replies

Tiny
JAMES W.
  • MEMBER
Ozzy, Lets try a little experiment. With the engine at a warm idle, all accessories off, check the voltage at the battery posts with a volt meter. You should have between 13.5 to 15 volts. Then turn your head lights on and check voltage. Then turn your blower fan on high. If you had 13.5 volts to start, with all the load added, the volt reading should not drop below 13 volts. Let us know what you find and we can go from there.
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Tuesday, November 18th, 2008 AT 7:45 PM
Tiny
LIGHTHORSEOZZY1
  • MEMBER
Hey James,

I have done voltage tests at the battery and I have done voltage tests, with everything turned on. The charging system still goes below 13.0 and does not return to 13.0. With all off and idling, the volts will barely come back to 13.0. I have done all this repeatly over and over and cannot seem to find the problem. What else do I need to do or check? Like I said, I have replaced battery and alternator together so many times and it seems to do the same thing, after short period of time. I don't know, if there was a issue problem with the firebirds around that time or not, that had this problem. Something is drawing the current down. By the way, I have replaced the Starter a couple of times as well. All connections are tight and snug. I sure hope you know the problem I am facing with this issue. Thanks
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Wednesday, November 19th, 2008 AT 3:17 AM
Tiny
JAMES W.
  • MEMBER
We're going to backup here a little bit. You mentioned you had changed batteries and alternators in the past. What was wrong with the old units? This could be a valuable clue. I checked past service bulletins and could find nothing on your problem. Let me know.
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Saturday, November 22nd, 2008 AT 12:36 PM
Tiny
LIGHTHORSEOZZY1
  • MEMBER
Hey James,

The Batteries I changed were quite new, but for some, the plates shorted out inside. The Alternaters, the regulator inside went bad. Again, changed these out, sometimes together and sometimes separate. These parts were quite new. Thats why, I thought it was very odd, that this woud keep happening all the time. On the gauge in the car, the indicater showed the charging rate at 13.0 amps. At times, the indicater would dip way down to 9.0 amps and shoot right back up to 13.0. When I turn on the heater fan and lights, the indicter would dip to 11.0 amps and while running down the road, the indicater would not return to 13.0 amps. For some apparent reason the amp gauge would not get past 13.0 amps. What would draw the power down or possibly short the battery and Alternater out? I know there is not to much to a charging system and this is very puzzling. Are there any fusible links in the charging system, in this year of car? James, are we overlooking something vey small, that would do all this? I am still racking my brain. I want to also Thank you for helping me with this nightmare. Ozzy
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Sunday, November 23rd, 2008 AT 6:25 AM
Tiny
JAMES W.
  • MEMBER
Ozzy, your right, this is a strange one. When we find the problem, it's going to be something very simple. All we have to do is "find" it. Is the battery ground to the engine good? You can check this with a jumper cable. Also, check battery ground to car body. Do you have, or have access to, a fax #? In the interim, I'm going to pull up some wiring diagrams for your system and see what I can find. One last thought, do you have a rear window defroster?
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Sunday, November 23rd, 2008 AT 12:02 PM
Tiny
LIGHTHORSEOZZY1
  • MEMBER
Hey again James and a Happy Thanksgiving,

Well, I changed out the negative battery cable, including the one to the body. Still there was no change. I do have a defroster but it is not hooked up. I do not have a fax but I do have a cell phone number, which I will give you, incase you need it: 912-507-2455. James, I checked the positive cable and it is fine. Like I said before, I know there is not much to the charging system. After I installed the battery cable, I fired up the car and it still stayed at 13.0. I then turned on headlights and ac, with full high fan and it still dropped, with very little recovery to even 13.0. Is there anything my car can be hooked up to, that can pin point the exact problem to this mystery and I mean exact? This includes wiring, ground, fusible links, etc. I do appreicate you helping me with this. Ozzy
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Thursday, November 27th, 2008 AT 6:12 PM
Tiny
JAMES W.
  • MEMBER
Ozzy, we're going to try a little experiment here. I'm not one to fully trust OEM gauges. Not that yours isn't reading right, but we need to make sure. If you have, or can beg, borrow, steal a volt meter and connect it accress the battery terminals and see what it is reading before you start the car and the reading when the car is running without any accessory load. Then, turn on the lights, blower and anything else you have. See what the meter is reading then. I haven't ruled out a bad alternator yet. Let me know what the readings are. I still have one more test, depending on what the readings are. Depemding on what type of meter you have, use the 20 volt scale or whatever it has close to that.
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Thursday, November 27th, 2008 AT 9:39 PM
Tiny
LIGHTHORSEOZZY1
  • MEMBER
Hey James,

Ok, I used the Voltmeter at the alternater and it read 14.2. I turned on the ac and headlights and it still was at 14.2, which is normal reading. Now, I am thinking, the gauge on the dash is incorrect. Found out something else. I have a power amp for my sound system, which is a 1000w power amp. I was told, that your alternater couldnt handle all that and the regulator was burning up. Is this all true? I was told also to get a digital meter for my dash, for more accurate reading and if this is correct, what is good good brand? I was also told to get a alternater with higher output. If this is correct, what should I get? I will be awaiting your reply and thanks James. Ozzy
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Friday, November 28th, 2008 AT 12:18 PM
Tiny
JAMES W.
  • MEMBER
WOOOOW' I didn't know they made an amp that size that would run on 12 volts. Normally, when a person posts a problem like yours, one of the first questions I ask is, "Do you have any aftermarket equipment installed?" I missed on yours. To answer your queations, you may havr trouble finding a digital or analog volt gauge that will fit in place of the old one. You'll just have to see what's available. On the alternator, for sure that kind of load is what is taking out the regulators. The alternator you have is probably only 45 amp. I think you can go up to 90 amp and still have it fit the same brackets. You'll have to check with the parts store to know for sure. Anyway, for your application, there is no such thing as "too" big.
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Friday, November 28th, 2008 AT 9:37 PM

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