Hey there everyone, I just though that I would log my efforts from yesterday and today to find a parasitic draw in my 1990 civic hatchback.
So, I drove to Portland and back the other day. My 12v outlet was not working prior to the journey and I wanted it for charging my phone, etc. I took off the center lower console and made quick work of the problem. I then made the journey and came back in the same day (10 hours of driving). The following morning the car would not start. I immediately thought of Occam's Razor in an attempt to diagnose the problem.
I knew that the battery was good as it is fairly new. I hypothesized that there must be some kind of a draw. The amp meter connected in line with the negative terminal indicated a 1.5 amp draw at 8 volts. After charging the battery, that draw went up to 2 amps at 12 volts. I started pulling fuses. I removed every single pull fuse to no avail.
After some searching, I decided I'd better start unscrewing main fuses. I started with the 60 amp fuse in the engine bay fusebox. The draw went to 0.00 amps immediately. That particular fuse is what connects both wires at the fusebox held in by screws which sit directly next to each other. Following the wire led me to a loom which ran under the intake. That loom split and connected to the alternator. I removed the wire off the alternator (charging wire held on with a 10mm nut) and the draw disappeared. In an attempt to be thorough, I made a jumper cable and connected it to the alternator on one end and the positive terminal of the battery on the other, having disconnected all other wiring from the battery. I measured the draw again. 1.5amps at 8v. The alternator is draining my battery while the car is off.
My suggestion for all those who find themselves in a similar situation is to pull fuses one at a time while monitoring the draw on the battery. If no fuse eliminates the draw consider the objects that have a static connection to the battery under all circumstances. That is the starter, the alternator, etc.
I hope this helps someone in a bind at some point.
All the best!
So, I drove to Portland and back the other day. My 12v outlet was not working prior to the journey and I wanted it for charging my phone, etc. I took off the center lower console and made quick work of the problem. I then made the journey and came back in the same day (10 hours of driving). The following morning the car would not start. I immediately thought of Occam's Razor in an attempt to diagnose the problem.
I knew that the battery was good as it is fairly new. I hypothesized that there must be some kind of a draw. The amp meter connected in line with the negative terminal indicated a 1.5 amp draw at 8 volts. After charging the battery, that draw went up to 2 amps at 12 volts. I started pulling fuses. I removed every single pull fuse to no avail.
After some searching, I decided I'd better start unscrewing main fuses. I started with the 60 amp fuse in the engine bay fusebox. The draw went to 0.00 amps immediately. That particular fuse is what connects both wires at the fusebox held in by screws which sit directly next to each other. Following the wire led me to a loom which ran under the intake. That loom split and connected to the alternator. I removed the wire off the alternator (charging wire held on with a 10mm nut) and the draw disappeared. In an attempt to be thorough, I made a jumper cable and connected it to the alternator on one end and the positive terminal of the battery on the other, having disconnected all other wiring from the battery. I measured the draw again. 1.5amps at 8v. The alternator is draining my battery while the car is off.
My suggestion for all those who find themselves in a similar situation is to pull fuses one at a time while monitoring the draw on the battery. If no fuse eliminates the draw consider the objects that have a static connection to the battery under all circumstances. That is the starter, the alternator, etc.
I hope this helps someone in a bind at some point.
All the best!
Honda-Tech Member
Great write up for parasitic draw diagnostics. Just to continue on a bit; to pin point the cause of the problem once after discovering the problematic circuit would be discounting portions of wire harness plugs as well as even tugging on the suspected bad wire harness while watching your multimeter for drop/fluctuations which will help isolate the area of problem.
Another few tips look out for: any aftermarket electronic equipment such as alarms, gauges and stereo systems that have been tapped into factory wire harness and especially self tapping screws that may have been screwed into your harness during installation of aftermarket equipment can be a major issue over time which I have seen many times over the years.
Another few tips look out for: any aftermarket electronic equipment such as alarms, gauges and stereo systems that have been tapped into factory wire harness and especially self tapping screws that may have been screwed into your harness during installation of aftermarket equipment can be a major issue over time which I have seen many times over the years.