KaptKane

New Member
Jun 19, 2018
26
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77
SW FL
So...I drove my 90 GT the other evening as I often do. Didn't notice anything unusual while driving it but then again, I only drove it a half mile. Brought it home and parked in the garage.
Next morning I went to use it and the battery was almost dead. Wouldn't start. Every once in a while it would crank slow (like the battery was low, timing was advanced, starter get old or too hot) but it always started. I figured, battery must be bad. Checked the install date and it was only 2 1/2 years ago.
Being the "know it all" that I am I went and bought a new battery and put it in. I charged it for at least 6 hours. Went out this morning and it was almost dead again! WTF?
I disconnected the negative battery cable and put a meter between the cable end and the battery post. Showing a 12v draw. I (in sequence) removed every fuse and I still had the draw. I removed the radio and disconnected it (figuring the radio memory was the draw). No change.
I started it and the volt meter is not showing a charge! Shows about 8 volts while running which I"m thinking;
Alternator is bad now (also)
I disconnected the wires from the alternator and I still have the draw.
Now, I'm stuck.
Ideas?
Thanks as always.
Kane
 
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Blown88GT

Founding Member
Nov 13, 1999
2,144
505
164
Palm Beach Gardens, FL
So...I drove my 90 GT the other evening as I often do. Didn't notice anything unusual while driving it but then again, I only drove it a half mile. Brought it home and parked in the garage.
Next morning I went to use it and the battery was almost dead. Wouldn't start. Every once in a while it would crank slow (like the battery was low, timing was advanced, starter get old or too hot) but it always started. I figured, battery must be bad. Checked the install date and it was only 2 1/2 years ago.
Being the "know it all" that I am I went and bought a new battery and put it in. I charged it for at least 6 hours. Went out this morning and it was almost dead again! WTF?
I disconnected the negative battery cable and put a meter between the cable end and the battery post. Showing a 12v draw. I (in sequence) removed every fuse and I still had the draw. I removed the radio and disconnected it (figuring the radio memory was the draw). No change.
I started it and the volt meter is not showing a charge! Shows about 8 volts while running which I"m thinking;
Alternator is bad now (also)
I disconnected the wires from the alternator and I still have the draw.
Now, I'm stuck.
Ideas?
Thanks as always.
Kane
I don't understand what you mean by "draw".
1. I disconnected the negative battery cable and put a meter between the cable end and the battery post. Showing a 12v draw.
Volts isn't a "draw". Amps are a "draw".
2. I disconnected the wires from the alternator and I still have the draw.
The "wires" have a connector. You removed the connector(s). Unless you have a 3G, which has 2 connectors & 1 wire.
3. Alternator is bad now (also).
Get it tested.
 
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jrichker

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Mar 10, 2000
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Dublin GA
lowendmac.com
So...I drove my 90 GT the other evening as I often do. Didn't notice anything unusual while driving it but then again, I only drove it a half mile. Brought it home and parked in the garage.
Next morning I went to use it and the battery was almost dead. Wouldn't start. Every once in a while it would crank slow (like the battery was low, timing was advanced, starter get old or too hot) but it always started. I figured, battery must be bad. Checked the install date and it was only 2 1/2 years ago.
Being the "know it all" that I am I went and bought a new battery and put it in. I charged it for at least 6 hours. Went out this morning and it was almost dead again! WTF?
I disconnected the negative battery cable and put a meter between the cable end and the battery post. Showing a 12v draw. I (in sequence) removed every fuse and I still had the draw. I removed the radio and disconnected it (figuring the radio memory was the draw). No change.
I started it and the volt meter is not showing a charge! Shows about 8 volts while running which I"m thinking;
Alternator is bad now (also)
I disconnected the wires from the alternator and I still have the draw.
Now, I'm stuck.
Ideas?
Thanks as always.
Kane

Troubleshooting battery drains

Typically it is something draining the battery. Small things like glove box or courtesy lights are often the culprits. If you have an aftermarket stereo or alarm system, it is also suspect.

The ideal method is to disconnect the negative terminal, and connect a Digital Multimeter (DVM) between the negative terminal on the battery and the negative cable. Set the DVM on a low current scale of 2-5 amps if it doesn't auto-range. Watch the current draw, and then start pulling out fuses. When you see a sudden drop in the current, that circuit is the likely culprit.Note that the computer, radio & clock will draw less than 1/10 amp to keep the settings alive.

See http://assets.fluke.com/appnotes/automotive/beatbook.pdf. You will need the Adobe Acrobat viewer which is also a free download – http://www.adobe.com/products/acrobat/readstep2.html

If you can’t find the current drain by pulling fuses, then the alternator is suspect or any aftermarket sound or lighting equipment that may be on the car. Disconnect the alternator output power plug, then disconnect any aftermarket sound or lighting equipment while watching the current on the DVM.