Hello, I’m hoping someone can look at my voltage drop test readings on the brake light circuit? I am a bit worried by the readings on the positive wire.
I have not done voltage drop tests before but YouTube helped & also did them on my headlights & tail lights to see what’s what. So I got the gist of what’s going on & it seems you should have under the battery voltage once all tests are done when added up & readings should be around 0.5v or less on a positive+ to positive+ or earth- to earth- wire. From what I have learned I have resistance I think in my positive wire but as I have never done this maybe it’s normal on the brake light circuit?
I can only think something maybe feeding off that positive for power? I have attached the wiring diagram for EA - ED. Any help would be really appreciated. Thanks
I ran 2 tests. Car off was done after other tests & is why voltage is a bit low. For the test when car was running, was done after a drive about 15mins later.
Car off
Battery voltage: 12.29v
Drivers side
+ batt to + brake light wire: 1.90v
- batt to - brake light wire: 0.10v
+ brake light wire to – brake light wire: 9.90v
Total: 11.90v
Total of 0.39v under battery voltage
Passenger side
+ batt to + brake light wire: 2.00v
- batt to - brake light wire: 0.16v
+ brake light wire to – brake light wire: 9.66v
Total: 11.82v
Total of 0.47v under battery voltage
Car running
Battery voltage: 14.25v
Drivers side
+ batt to + brake light wire: 1.96v
- batt to - brake light wire: 0.23v
+ brake light wire to – brake light wire: 12.20v
Total: 14.39v
Total of 0.14v OVER battery voltage
Passenger side
+ batt to + brake light wire: 1.93v
- batt to - brake light wire: 0.14v
+ brake light wire to – brake light wire: 12.06v
Total: 14.13v
Total of 0.12v under battery voltage
Light on rear parcel shelf in rear window
+ batt to + brake light wire: 2.00v
- batt to - brake light wire: 0.40v
+ brake light wire to – brake light wire: 11.90v
Total: 14.30v
Total of 0.05 v OVER battery voltage
Voltage at brake light switch with ignition on/car off
11.11volts
