I am continuing to have a battery problem with my 67 big block coupe. After replacing the alternator I have had repeated problems with the battery discharging, apparently hen the engine is off. I am unable to find any evidence of a current drain. In fact, I get no reading with an ammeter across the battery posts. After driving the car a few times and leaving it overnight, the battery is dead. The battery checks out ok and holds a full charge when charged with a charger. I have disconnected my glove box light and confirmed that all accessories are off when the ignition is locked. The new alternator tests out ok. Could I be having a problem with the voltage regulator and how do I test it? Is there anything else I am missing? This problem has been hounding me for a couple of months now. Any help or insight would be much appreciated.
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Re: 67 Battery Drain
I don't exactly know what you mean about "no current across the battery posts"
To test for a small current draw, you need to place the ammeter in series with the "load". In other words disconnect one battery lead and clip lead in the ammeter. DON'T attempt to start the car as you'll probably fry your meter....
If there is a drain on the battery you'll see it on the meter. I assume you are using an ammeter that can read small currents...(example .01 amps). Another method is to place the car in a dark area and just touch a battery cable to the post to see if you can draw a small arc...
You can also isolate the battery from the car by charging it and leaving a cable disconnected for the 24 hrs and see if the battery will maintain a charge... you may have a bad cell. -
Re: 67 Battery Drain
John,
Once you have the ammeter connected per Steve's recommendation you can isolate the problem circuit by removing one fuse at a time. Happy hunting.
RandyComment
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Re: 67 Battery Drain
John,
If you don't find a battery drain, maybe the voltage regulator setting is too high and you are cooking the battery, (or possibly too low).
Do you have to always add water to the battery, and does the battery seem to charge up too quickly. This is what happened to me. Finally went with a new battery and adjusted the voltage on the regulator. I use a "volticator" which plugs into the cigar lighter to check the voltage regulator operation, but there are other more complicated ways to do it.
See your service manual on the voltage regulator adjustment, it's just one adjustment screw.
Jerry Fuccillo
#42179Jerry Fuccillo
1967 327/300 Convertible since 1968Comment
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Re: 67 Battery Drain
Hi John do as Steve said but you can use a volt meter instead,if you dont have an amp.meter.Take off one battery cable and put the meter in series with the battery.(EX remove pos cable from battery post, attach pos lead of the meter to the pos battery post and the neg.lead of the meter to the pos battery CABLE.) The meter will read battery voltage if you have a draw, remember first to touch the battery cable to its post for a couple of seconds to get the clock started, good luck Phil 8063Comment
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Jack, Where are you *NM*
Jerry Fuccillo
1967 327/300 Convertible since 1968Comment
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I'm here...
First, a good auto electric shop ought to be able to attach their roll-up diagnostic cart to your car and trouble shoot the problem in 15-20 minutes flat. That doesn't include the fix...
But, if you really want to do the job yourself, you can. Most auto electric shops have a simulator/exerciser box for voltage regulators which will quickly verify if a given V-Reg is working properly. BUT, if you start the engine + rev it and observe the ammeter showing charge + a VOM across the battery posts shows battery voltage has climbed above pre-start conditions (11-13 VDC) and has reached the normal driving/charging level (13-15 VDC), then you're on a fool's errand to question the V-Reg...
Popping fuses one at a time to eliminate circuit branches that are shorting is MARGINALLY effective. That approach presumes the problem lies with a branch circuit that is fused, and not all circuits are fused. Sometimes problem(s) lie in unswitched or unfused circuits that are active all the time like interior lights, cig lighter, or engine B+ buss (side of horn relay in the engine compartment).
Plus, alternators CAN be flakey yet still test 'good' depending on how thorough the alternator tester is. The AC-DC diode bridge in the alternator consists of six diodes to provide a 3-phase rectifier bridge. If one (or more of the diodes) is 'sick' (poor reverse bias profile and leaking due to electrical overstress and junction puncture), it'll drain the battery when the ignition is switched off and this will NOT show on your ammeter!
Typical auto parts store alternator testers are simple 'go, no-go' setups, designed to verify the alternator HAS the ability to output current. If two of the three rectifier stages are working properly and one is dead or 'wounded' the alternator will still generate power and pass this simple test...
Real electrical pros test alternators by pacing them across their full dynamic range (RPM vs. current output) and monitoring the DC current waveform on an oscilloscope as well as testing them LONG ENOUGH to get the alternator hot (minor diode junction damage may only surface at elevated temperature).
Bottom line: you can go step by step troubleshooting the problem(s) yourself, but if you're up against something tricky, you might well miss it. The roll-up diagnostic cart most auto electric pros have will fully verify the integrity of the battery, v-reg, and alternator in one fell swoop for you quickly and accurately!Comment
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Re: I'm here...
Jack, You're advice sounds good. I think I'm frustrated because I can't isolate the problem on my own. I replaced the alternator a couple of months ago based upon the diagnostic test on my charger indicating that the old alternator was not generating current. The battery will hold a full charge when isolated from the electrical system. Current drain is 7.6 milliamps when the battery is installed in the system which appears to be the current drawn by the quartz clock movement. If I disconnect the clock, there is no current drain. If I drive the car and then leave the battery connected, the battery is discharged within a couple of days. I guess that it's time to have the system checked professionally as you suggest to avoid further frustration on my part.
Thanks again to all who reponded.Comment
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Re: I'm here...
John -
The clock draw isn't continuous (assuming you have the original electro-mechanical clock) - only when the winding solenoid fires every couple of minutes. If the draw is continuous, then there's a problem in the clock solenoid.Comment
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Re: I'm here...
It's a quartz clock with continuous draw. I have driven the car a couple of days now and the battery remains fully charged. Maybe I'll just keep an eye on things for a while and see if it discharges again.Comment
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