Auto electrical and batteries
Electrical Fault Diagnostics
Electrical faults get fixed by measuring, not by replacing parts and hoping. We trace parasitic drains, intermittent faults, bad earths and dodgy accessory wiring at our Moorooka workshop, using a meter on the circuit and the wiring diagram for your model. Call 0402 723 464.
Symptoms
Symptoms that land in this category
- The battery is flat after the car sits for two or three days
- A window, mirror, central locking or interior light has stopped working
- Lights dim or flicker at idle and brighten when you rev
- The radio or the dash resets itself while driving
- A fuse keeps blowing, sometimes weeks apart
- Something works when the car is cold and stops once it warms up
- The fault appeared shortly after a dash cam, sound system, driving lights or a UHF went in
Parasitic drain
Parasitic drain, and why it takes a while
Every modern car draws a small amount of current after it is locked. Alarm, clock, keyless entry receiver and a queue of control modules all sit at a very low draw once they have gone to sleep. A healthy car settles somewhere in the tens of milliamps.
The problem is that they do not all go to sleep at once. Some modules stay awake for 20 minutes, some closer to an hour, and a few wake again when a door handle is touched. Measure straight after locking the car and everything looks like a drain, which is how good components get replaced for no reason.
So the test is a patient one. We connect an ammeter or a clamp in a way that never breaks the circuit, wait for the car to properly go to sleep, record what it settles at, and only then start isolating circuits until the draw disappears. Finding a 400 milliamp drain that flattens a battery over a long weekend can take an hour of sitting and watching before anything is touched.
Earth faults
Earths cause the strangest faults
Most weird electrical behaviour traces back to a poor earth rather than a failed component. Current needs a clean path back to the battery, and that path runs through strap connections bolted to the body and the engine.
Salt air, road grime and age corrode those connections. What you get is not a dead circuit but a resistive one, so the headlights dim when the indicator flashes. A continuity test will often pass a bad earth. A voltage drop test under load is what actually finds it, and that is the test we use.
Intermittent faults
When it only happens sometimes
A fault that appears once a fortnight is the hardest work in the trade, and honesty about that matters more than confidence. We start with freeze frame data and stored codes, because the car remembers conditions you have forgotten.
Then we try to reproduce it — load testing a circuit, wiggle testing a loom section, heating a connector or running water over a suspect area. If it cannot be reproduced on the day, we say so and agree what to do next rather than replacing something expensive to look decisive.
Aftermarket accessories
When the problem started after an accessory went in
A large share of the electrical faults we see arrive with a story that begins "it started after we had the driving lights fitted". The usual problems are the same ones every time. Power tapped from a circuit that was never meant to carry it. Scotchlocks that cut half the strands in a wire and corrode from the inside. An accessory wired to a permanent live instead of an ignition-switched one, which is a parasitic drain by design. Fuses missing, or fitted so far from the battery that the whole run is unprotected.
We are happy to sort that wiring out properly, and we will run new circuits with the right fusing rather than patch the existing mess.
Common questions
Frequently asked questions
How long does it take to find a parasitic drain?
Commonly an hour or two, because a chunk of that is waiting for the car's modules to go to sleep before any reading means anything.
What is a normal draw on a parked car?
Usually somewhere in the tens of milliamps once everything has shut down. Big variations from model to model, which is why we compare against the specification for your car.
My battery is new and it still goes flat. What now?
That is a strong sign of a drain or a charging fault rather than a battery fault. Both get tested here.
Can you find a fault that only happens sometimes?
Often, yes, but it takes longer and we will be straight with you about the odds before you spend money.
A fuse keeps blowing. Can I just fit a bigger one?
No. The fuse is protecting the wiring, and a bigger fuse turns a dead circuit into a fire risk. The short needs finding.
Can you fix wiring done badly by someone else?
Yes, and it is a regular job. Tell us what was fitted and roughly when so we know where to start.
Do you work on European electrics?
Yes, along with diesel, 4WD, fleet, commercial, hybrid and electric vehicles.
Will you need the car for the day?
Sometimes. Leave it with us where you can, because a rushed electrical diagnosis is a bad one.
Do you have wiring diagrams for my model?
We work from model-specific data rather than generic diagrams, which matters on later European vehicles especially.
Something drains only when it rains. Is that a real thing?
Very much so. Water finds its way into connectors, boot lids and door looms, and the fault follows the weather.
Book an electrical diagnosis
Measure first.
Replace only what failed.
Monday to Friday 8am to 5pm, Saturday 8am to 3pm. After-hours key drop available. All major cards and cash.