Electrical and battery · Carrollton, Texas
A flat battery is usually a symptom.
Parasitic drain diagnosis, battery replacement and wiring harness repair, found by measurement rather than by replacing the battery twice.
The car that goes flat
A McLaren that will not wake up after two weeks in the garage is the single most common electrical complaint we hear, and the battery is very often innocent.
A shorted door-lock sensor will draw current overnight, quietly, with the car locked and everything apparently asleep. Fit a new battery and the car is fine for a fortnight, which is exactly long enough to convince an owner the problem is solved.
Finding it means measuring the draw with the modules properly asleep and then isolating circuit by circuit. It takes patience and the factory tool, and it is a great deal cheaper than the alternative of replacing batteries indefinitely.
The work
Electrical diagnosis is a measuring job. Nothing is replaced until the draw or the fault has been located and shown to you.
The car is allowed to go properly to sleep, which takes longer than most people expect, and then current draw is measured against the expected figure. Only once there is a number worth chasing do we start isolating circuits.
Fuse by fuse and module by module until the draw disappears, then a physical inspection of whatever that circuit feeds. The shorted door-lock sensor is a frequent culprit, and it is invisible until you have narrowed the field to it.
Battery health, charging output and the car's own battery protection strategy are all tested. Where a battery is genuinely finished it is replaced with the correct specification, including the Gen 3 battery on cars that call for it.
Some faults are mechanical damage to wiring rather than a component failure.
In the cabin
Body and comfort modules scanned for the faults that pull current overnight, door lock sensors first among them.
Overnight current draw measured at the battery, with the offending circuit named rather than the part swapped.
Switchgear, displays and controls exercised end to end, so intermittent faults are caught on our watch, not yours.
How the job runs
Every module read on the factory tool, including stored intermittent faults.
Car allowed to sleep, current measured against the expected figure.
Circuit by circuit until the draw is located and photographed.
Fix, then a second overnight measurement before the car goes home.
Drain diagnosis usually needs the car overnight, because the modules have to be genuinely asleep for the reading to mean anything.
Electrical and battery
Every circuit accounted for, overnight drains included.
Where we work
Drain diagnosis needs the car here, not a visit. We collect and return across Dallas-Fort Worth so that is rarely an inconvenience.
If the car is dead in the garage, we will collect it. Jump-starting a modern McLaren incorrectly can create faults that outlast the flat battery.
If your car lives in climate-controlled storage with us, this is the fault we catch before you ever notice it.
Why March Motorsports
Electrical work is the easiest place for a shop to charge you for parts and solve nothing, because a new battery always makes the symptom go away for a while.
We measure first, show you the reading, and confirm the fix with a second overnight test before the car leaves.
A current figure before and after, so you can see the fault was actually fixed.
The shorted door-lock sensor draw is familiar ground here.
A second sleep test before handover, not a hopeful handshake.
Areas we serve
Our Carrollton workshop serves owners throughout Dallas-Fort Worth, with collection and delivery available across the Metroplex and enclosed transport arranged statewide.
Explore all service areasWhat owners say
1 month agoRecently dropped a McLaren 600LT off for a PPI. Dalton and the team were super helpful. They know these cars well and identified issues I don't believe another shop would have caught.
1 month agoDalton at March Motorsports is the real deal. He answered every question honestly, never pushed me, and went out of his way to help. Their inspection work is thorough and transparent.
1 month agoMcLaren has been my dream car to own and March Motorsports helped me from start to finish. I recently purchased a McLaren 720S from March Motorsports and it has been an amazing experience.
2 months agoDalton and the team have taken excellent care of my 2019 McLaren 570S for 2 years, from regular service to complex repairs, exhaust and ECU performance upgrades.
2 months agoDalton helped me out tremendously. Couldn't have asked for a better experience. He directed me the right way on a McLaren I was looking to buy.
2 months agoPerformed 6 year service on my 600LT Spider. 5/5.
2 months agoAll work was performed, as promised, to their and my exacting specifications. Dalton was very responsive throughout the whole process.
2 months agoExceptional work, honest communication, and true expertise. If you own a McLaren, this is the kind of mechanic you want in your corner.
1 month agoRecently dropped a McLaren 600LT off for a PPI. Dalton and the team were super helpful. They know these cars well and identified issues I don't believe another shop would have caught.
1 month agoDalton at March Motorsports is the real deal. He answered every question honestly, never pushed me, and went out of his way to help. Their inspection work is thorough and transparent.
1 month agoMcLaren has been my dream car to own and March Motorsports helped me from start to finish. I recently purchased a McLaren 720S from March Motorsports and it has been an amazing experience.
2 months agoDalton and the team have taken excellent care of my 2019 McLaren 570S for 2 years, from regular service to complex repairs, exhaust and ECU performance upgrades.
2 months agoDalton helped me out tremendously. Couldn't have asked for a better experience. He directed me the right way on a McLaren I was looking to buy.
2 months agoPerformed 6 year service on my 600LT Spider. 5/5.
2 months agoAll work was performed, as promised, to their and my exacting specifications. Dalton was very responsive throughout the whole process.
2 months agoExceptional work, honest communication, and true expertise. If you own a McLaren, this is the kind of mechanic you want in your corner.
Book it
Tell us how long the car sits between drives and whether it is on a maintainer. Both change what the reading should be.
Questions
Most often a parasitic draw rather than a bad battery. A shorted door-lock sensor is a known cause and will pull current overnight with the car locked and apparently asleep.
It will mask it. A maintainer is sensible for a car that sits, but it should not be the reason a car with a genuine fault stays alive.
The car is left until every module is properly asleep, the current draw is measured against the expected figure, and then circuits are isolated one at a time until the draw disappears.
Usually overnight, because a reading taken before the modules have gone to sleep tells you nothing useful.
We would rather you did not. Incorrect jump-starting on these cars can create module faults that cost more than the recovery would have.
Yes, where the car calls for it, including the Gen 3 battery, with the specification recorded on your invoice.
Yes, and we reroute the repaired section so the chafe that caused it cannot recur.
Frequently, yes. Low voltage produces a scattering of unrelated messages, which is why the first step is a full module scan rather than chasing each message separately.
