Quote:
Originally Posted by 911pcars
The warning is to NOT ground a circuit without a load (electric motor, bulb, etc.) in the circuit or to bypass the load circuit path to ground with test wires.
Sherwood
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To which I PM'ed:
Quote:
I am an electrical N00b, so I don't understand what this means. Can you translate it explain to your wife or mother?
My "safe" plan:
1) Detach negative terminal cable.
1b) Disconnect hood lamp bulb
2) Connect black probe/lead to negative battery post
3) Connect red probe/lead to the negative terminal cable.
4) Read measurement
5) Re-connect hood lamp bulb
6) Read measurement
Can you explain what to do to create the problem you described?
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Meter connection to observe parasitic current drain is correct. You can leave the bulb in place.
If the meter displays more than ~160 Ma (milli-amps), excessive current is flowing in the electrical system, maybe not enought to blow the fuse, but enough to drain the battery overnight.
The next step is to temporarily remove each fuse from the fuse box in turn while observing the current display. If the current level decreases, you have partially identified the offending electrical branch circuit. That particular fuse could protect a series of branch circuits, powering several loads (accessories; e.g. cigarette lighter, glove box, dome light, etc.).
Once you've identified the circuit causing the excess current draw (fuse # X, you must refer to the electrical schematic diagram and identify the circuit/load(s) protected by fuse X). It may be the circuits providing electricity to the cig. lighter as well as the blower motor, etc.).
Make a copy of the circuit, then with a transparent marker, highlight the circuit wires and branch circuits leading away from fuse X all the way to ground (return path of electricity to battery).
For example, let's say you have identified that removing fuse X changes the current reading on the current meter and fuse X protects the branch circuit(s) that provide electricity (current) to the cig. lighter and glove box. One of these loads is causing the abnormal current drain. Here's how to isolate which load is causing the excessive current drain.
While observing the meter, disconnect the source wire to the cig. lighter. Does the meter change (reduced current)? If so, you have identified the source of the parasitic current draw. If not, reconnect, then disconnect the source wire to the glove box bulb and observe the meter.
This identify and isolation procedure is the same for any circuit protected by a fuse. Obviously, if the current drain is high enough, current flow will cause excessive heat and cause the fuse to melt (blow) and thus opening the circuit to prevent continuous current flow. Parasitic current flow isn't normal nor is it high high enough to flow the fuse. It will, however, slowly drain the battery, similar to leaving the dome light ON overnight.
Here's a source that illustrates a "short circuit".
Short Circuit (Series)
Suggest reading about basic DC electricity to understand the elements that allow electricity to perform work. The link above provides more pages you can read. Electrical malfunctions begin here:
DC CIRCUIT FAULTS
BTW, removing and replacing the bulb (load) won't reveal a short circuit. Excessive current with switch off typically indicates a malfunction somewhere in the circuit path that bypasses the normal load (bulb, in this case).