Do I have a short? - Team Camaro Tech
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post #1 of 2 (permalink) Old Jun 8th, 03, 02:27 PM Thread Starter
Join Date: Jun 2003
Location: Newtown, PA
Posts: 2

This will be a long post - but I want to give you some background as to what is going on and what I have done to check it.

I recently replaced my engine wiring harness on my 68 RS/SS with a kit from Classic Industries. The system wouldn't charge, and (with the help of a good electrical guy) I discovered that the harness switched the field and output wires from the alternator to the regulator (it was incorrectly wired). Reversing these, the system seemed to work great.

However, and this is where my problem starts, the next day, I was working on fixing a bad ground on a parking lamp, and left the ignition key in the "on" position overnight. It appeared to only drain the battery, so I charged it, started it up, and it seemed to run great.

When I went to start it the next day, there was nothing.

I appear to have a short - the interior courtesy lamps stay on continually, the tach seems to be registering 250 RPM with the engine off, and or course, the engine won't run.

I charged the battery up to 13 Volts, and let it sit - it drained down to 8 Volts overnight. When I put a digital volt meter across the battery terminals, I get 850 milliamps. When I pull off the negative terminal and put the voltmeter from the negative terminal to positive post, there is zero amps. Putting the meter in series between the negative terminal and negative post, I show 850 milliamps.

The last bit of information that I can offer is that if I disconnect the circuit charge lead which goes to the junction block near the battery, the courtesy lights go off.

So, after all that, can anybody give me a clue what to do? Do I have a short in the wiring, or did I ruin the ignition switch by leaving it on, or is it unrelated.

Also, can anyone confirm that the circuit charge lead does in fact go to the junction block, and then there is a lead to the positive terminal of the battery (both my assembly book, and the wiring diagram are unclear).

Thanks in advance for your help.

Ragtop 68 RS/SS is offline  
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post #2 of 2 (permalink) Old Jun 10th, 03, 07:25 AM
Join Date: Dec 2001
Posts: 56

Hi Ragtop...surprised no one has posted a reply yet.....first of all, regarding your ignition switch, you should not expect a problem on a 12 volt system, in my opinion. Regarding your battery, a typical reserve capacity is 2 hours, meaning the battery can maintain 25 amps at rated voltage for two hours. You are indicating just less than 1 amp overnight (i.e. 10 hours). If your battery is in good condition it should take about 50 hours to drain at 850 milliamps. Some batteries have an RC of about 1 hour, so it would then take about 25 hours to drain down at 850 milliamps. If it is occurring faster, as you indicate, either you are reading the wrong scale on the VOM or you have a short in your battery, or a battery near end of life. When I look for shorts I have someone holding the volt meter (VOM)which is connected in series with a disconnected battery cable and the corresponding battery post while I start disconnecting wires, one at a time, and when the VOM goes to zero, you have found the circuit that is suspect. For some circuits you will need to pull the fuses, which is much easier than disconnecting wires. It is a trial and error process, but you will find it eventually. Do the courtesy lights and tach come off the same circuit? Your post indicates that you effectively isolated the circuit in question when the courtesy light went off, like maybe it is connected to a constant 12 volts battery source. Hope this helps some...let us know how it turns out......Scott
ssfrebo is offline  
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