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Old 10-21-2005, 07:20 PM
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Can it be fixed?

Where to start?
OK, if I put an ammeter in series with the + battery terminal and the + battery cable, the reading is off the scale (>250mA).
The same thing happens if I put the ammeter in series with the + battery terminal and the alternator's #1 or #2 terminals (with all cables disconnected from the alternator).
If I put the ammeter in series with the + battery terminal and the stereo/door popper leads, the ammeter reads about 100mA.
Also, when I disconnect the + battery cable with the engine running, the engine dies, so I guess the alternator isn't charging the battery.
There is no voltage in the #1 alternator (thin brown) wire and the check engine light will never come on, but the bulb itself is fine.

Is there any hope for this poor old car's electrical system?

The vehicle is an 1985 Monte Carlo.

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Last edited by Jzarczyn; 10-21-2005 at 09:12 PM.
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Old 10-21-2005, 10:09 PM
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Doc here,

Are you saying WITH the alternator Disconnected, you are gaining a draw of over 1/4 amp static?

If so, you need to start pulling fuses until the draw goes away..Then troubleshoot that line or component until that draw goes away..and BE sure the dome light is defeated or it will show as a draw while testing..

Your draw at the battery, if computerized , with a modern CD/Radio and memory presets and mechanical (stock) Clock, should be no higher than 00.2 to 00.8 and no higher...



If without a Draw, and the Alternator hooked back up again, the car goes dead just sitting, measure again at the battery.

The draw should be the same as before..

If it is higher the Diode pack in the alternator is bad, and forward biasing just sitting..drawing power and flatting the battery. If it just won't charge at all the diode pack is bad..(most likely) OR the fuse link coming off the alternator is open..


You can either replace the diode sets (regulator and rectifier) yourself, for about 7 bucks each..or buy another alternator for starting about $30 bucks..(and take a chance it will work out of the box..)

The Brown wire has nothing to do with the Check engine light..it goes to a "BATT" light (if so equipped ) or a Gauge, via a small resistor..The check engine light is for Computer Issues only..(error codes) SOME will throw a "Low Voltage code if the computer senses below a window of dc power, but I think yours does not..

Disconnecting the battery cable while running is NEVER a good idea..ESPECIALLY on a computerized vehicle!

The resulting spark can set off an explosion on a gassing battery (a typical problem diagnosed this way in the past, when it keeps going dead, and a cell is shorted)

The spike, or Surge can cause tons of damage, (Especially if the diodes are bad and Inducing AC into the DC buss)..to the ECU like damaging quad buffers, or wiping the rom and ram clean of instruction sets..Scatter the MPU, or kill the system clock..Plus damage field sensors..(It's just not good for CMOS or HMOS architecture..)

Rebuild or replace on the alternator is your call, whatever you feel most comfortable with..





Find the other system draw (If I understood correctly, that is present without the alternator) and it should once again bring peace to the land of General Misery..

Don't rule out the possibility that the battery may be unserviceable too, get a load check on it first..

Doc
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Old 10-23-2005, 08:19 PM
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Thanks Doc.
The Battery I have is brand new.
I have rebuilt the alternator.
I think I am going to have to run a switched +12V (with a 10 ohm resistor) to the #1 (field) terminal on the alternator and flip the switch on for a second each time I start the engine. Does this sound OK?
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Old 10-23-2005, 08:39 PM
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Quote:
Originally Posted by Jzarczyn
Thanks Doc.
The Battery I have is brand new.
I have rebuilt the alternator.
I think I am going to have to run a switched +12V (with a 10 ohm resistor) to the #1 (field) terminal on the alternator and flip the switch on for a second each time I start the engine. Does this sound OK?
Doc here,

If the alternator is operating properly, you should not have to switch the field lines at all...If it poses a drain to the battery, then (new or not...) The diode bridge is defective..No other draw can be possible from the alternator static..

Battery that is new is NOT assurance of a good battery..

we had a guy on this forum a few posts ago..said "I just Replaced it..It's Not bad" but failed to test it going on the assumption that it was good...

After SEVERAL weeks of troubleshooting, and buying hundreds of Dollars of parts NOT needed..he pulled it and took it back to NAPA to load test it..

Sure enough..It was shot!!!!!

They gave him another, this time load testing it..Sure enough..It was shot too!!!!!

As well as every other battery on the shelf..they had to order out to replace the battery because none of their's were any good!

Always retest if in doubt!

Using a toggle switch will most likely burn up on you..you need a switch and a relay to handle the current at that point..the average toggle has contacts rated at 1 to 5 amps..The field puts out way more than that..

You may also have no grounds at all..(no charge reaching the battery) in that case, Do this:

Your ground should be set up as such, The battery cable ground to any handy bolt at or near the starter, from there, get a battery cable that has 2 3/8 ring terminals on it ($6 bucks at wally mart or auto parts place) and ground that to the frame..From the engine block ground at the starter, run 2 #10 wires, the first to the firewall, and the second to the alternator ground lug or mount bolt...

USE proper Star washers, Sheet-metal screws / bolts and locks, and burnish ALL the paint and grease from the grounding areas..this will give you a rugged reliable grounding system that will most likely outlast the car...

Doc
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