Coves4me

OK, I'm having some electrical issues with my 94 that I could use some help diagnosing. Here's what I have done so far: 1, replaced alternator with new 140-amp NAPA unit; 2. replaced stereo head unit with Alpine unit; 3. replaced battery with new DuraLast Gold type; 4. replaced all Mini fuses at dash near passenger door (none were blown); 5. replaced all Maxi fuses at both locations at battery (none were blown); 6. cleaned and wrapped wiring harnesses around battery to insure that none were broken or chafed; 7. cleaned both buss bars at fuse boxes and all positive connections; 8. cleaned all frame and engine block wiring ends and ground locations.

With that said (and with ignition off), I unhooked my ground cable at the battery (positive still attached) and checked for voltage drain between disconnected negative cable and the battery negative terminal. Voltage reads 12.81 volts. Sooooooooo, I started pulling fuses, one by one. First, both fuse boxes with Maxi fuses. Results: Nothing changed. Sooooooo, I pulled the mini fuses one by one. Results: Nothing changed. Then I went and disconnected my alternator wire. Results: Nothing changed. Still 12.81 volts.

The only other thing I am going to do is replace the positive battery cable to the starter. I don't like the way it runs along the engine block at the back and perhaps there is some chafing. The plastic wire sheath is brittle and comes off in pieces.

Where should I look next? Any suggestions what might be the problem?

Thanks in advance. Mark

RickinPhoenix

Check your amp draw instead of voltage and post the reading

Coves4me

OK, I checked across my disconnected negative battery cable and the negative post on my battery. With my multitester set at 10 Amps, I got a reading of 0.02. I'm assuming that means 20 milli-amps which is less than the 50 milli-amps threshold for the car. Based on this result, it would appear that I do not have a problem with current leakage. Am I correct?

Thanks in advance.

Mark

leesvet

I don;t think you have a leakage issue at all...

You have a LOT of electronics that have memory, and even power chips to maintain a memory in the ECM or dash modules. There will always be a tiny amount of energy thats stored in these devices. Thats probably what you are seeing.The fact that a battery will drain if left sitting on the floor speaks to the aura effect of the electrical field. This same effect happens in cars because the batterys mounting place is the ground or neg side of the field, so there is some, not much, but some energy thats going to show up with all the electronics that actually store some and use micro amounts.
12.8 off the battery post is fine. Your charge needs to be near 14(+) just after start-up, then drop to 12+ to 13.5 area when running with accessories on. (depending on which and how many) Its not unusual to see a system thats fully loaded with everything possible running to dip to 11.5 V at idle then rise sharply with any increase in rpm. These cars require a LOT of electricity. the HEI ignition system will suck the life out of a fully charged battery in 10 minutes driving time as it turns 12 V into 40,000V for ignition. Once it drops to 10V or less, the HEI can no longer fire and the engine stalls...

If you POS cable has the insulation plastic damaged, replace that asap. POS cables have been the start of more than one car fire...I do not care for that route they took either. Next time I'll wrap it around inside a heater hose or some other heavy duty insulating material and secure it somehow.

pcolt94

You said everything that you have done.

What exactly is the problem that you are having. Is the battery going dead or something like that?

RickinPhoenix

20 milliamp reading = you’re good : provided that was with all fuses in place and everything hooked up except the “negative battery cable / amp meter to take a reading set-up”. If not put those fuses in one at a time and check / record your readings.
Just for clarity you didn’t have any other problems other than noticing that there was 12.8 volts reading at the negative batt cable did you?
Whenever current flows you will read some voltage, don’t worry about that as voltage is only the pressure, (for illustration think of it as water pressure). In this case it’s the volume or current draw, (amps), that is a good indicator if there’s a problem.

Coves4me

Thanks RickinPhoenix. The 12.8 voltage was my only concern. After I read the amp draw, I went on Youtube and found several good videos on checking battery drain. Whooda thunk you could find that on Youtube. Amazing! Anyway I went to Radio Shack and got a 1 Ohm, 10 Watt resister and clipped it to the disconnected negative cable and the battery negative post, set my voltmeter to read current and Voila!, my findings were confirmed. 20 milliamps and I'm good to go. Thanks to all for the help.

Mark

pcolt94

Why would you connect a resistor in series and then put your meter in series (current mode) to read current. In the real world of commercial or military electronics, if you used the method of inserting a 1 ohm resistor in series, then you would read the voltage across the resistor. Then take that voltage and use ohms law to convert it to current. You do this when you don’t have an ammeter or other factors.

If you are going to insert the ammeter in series with your circuit, you don’t need the resistor. Resistors have to be chosen in regard to current and loading in order to get an accurate reading and an measurably voltage across the resistor.

In reality, the ammeter (or when putting your DVM into current mode) really measures voltage across a internal precision resistor and converts that voltage to a current reading and displayed. This is the same method if you used the 1 ohm resistor and measured the voltage across it and used the method I described.

My 94 uses just under 30ma. But when making that reading years back, I had to use a high scale like 10 amps to get a low enough shunt in the meter to activate and bring all systems up to initialize them. A lower scale did not " turn on the systems" and could not get an accurate measurement. All cars and other years may not have this condition and may be specific to the Fluke meter I am using.

I saw a YouTube recently video on making that measurement and the resistor was not used. But several years back I think I saw one that used a resistor but can't remember the details of it.