Help with parasitic battery drain, '99 DX hatchback

[5forfighting]

Hoping for advice from someone who's been down this road before....

My daughter's 1998 Civic DX hatchback (all stock) has had a prolblem with battery drain when it's not being driven on a regular basis. If the car isn't driven for a week or more, it's difficult to start. The previous owner replaced the battery but that didn't fix the problem.

This weekend I tested all the circuits for parasitic drain and found TWO issues:

ISSUE 1: The car has the original stock Honda AM/FM radio and single CD player. They are drawing 150 to 200 milliamps all by themselves. The CD player is actually on it's own circuit and appears to be drawing nearly all the amperage on this circuit....so I'll be off to get an aftermarket CD/radio installed. Easy enough.

ISSUE 2: The "interior lamp" circuit is drawing 80 to 100 milliamps, which is odd since the only "interior lamp" is the dome light. The ON/DOOR/OFF switch has a lot of slop in it so I'll be replacing that (if I can find one)....could that sloppy switch cause the extra draw, or should I be focusing on something elsewhere in that circuit?

Thanks in advance.

 

[RonJ]

ISSUE 2: The "interior lamp" circuit is drawing 80 to 100 milliamps, which is odd since the only "interior lamp" is the dome light. The ON/DOOR/OFF switch has a lot of slop in it so I'll be replacing that (if I can find one)....could that sloppy switch cause the extra draw, or should I be focusing on something elsewhere in that circuit?

Does the ceiling light or trunk open indicator light in the cluster remain on? The trunk light (if you have one), the cluster trunk indicator light, and the OBDII data link connector are on the same circuit as the ceiling light.

 

[5forfighting]

No dash indicator lights are on at all, not even a "door ajar". There is no trunk light and no dome light switch for the hatchback door, only for the driver & passenger doors. Can a datalink draw amps when the ignition is off?

 

[RonJ]

Can a datalink draw amps when the ignition is off?

I don't see why not. It gets power through fuse 43, which is independent of the ignition switch. As you can see from the circuit diagram below, the drain could also come from the integrated control unit or the dash fuse box, which are also on the fuse 43 circuit.

Why do you think there is a parasitic drain from the ceiling light circuit? Did you remove fuse 43 and the drain was reduced or eliminated?

 

[5forfighting]

I connected a multimeter in series between the negative battery cable and the negative post of the battery and found a draw of between 200 and 300 milliamps...can't be much more accurate since my meter jumps from a 200ma setting to a 10amp setting. Then I removed and replaced all fuses & relays on the inside box and the underhood box, checking for any change in amp draw. I also unattached/reattached every coupling I could get my hands on in the wiring harnesses under the dash.

Only two fuses made a difference, both of them in the underhood box:

- removing the 7.5A fuse labeled "Back Up (Radio)" dropped the draw by around 200ma
- removing the 7.5A fuse labeled "Interior Light" dropped the draw another 80ma or so. This is probably fuse #43 on your chart.

I've read that at one time, the Civic dome light shared a wiring circuit with the radio but I believe that was only '96-'98.

And thanks a lot for the posts and scans.

 

[RonJ]

The "Radio" fuse, also referred to as the 7.5A Back Up fuse (#47), protects the circuits for the radio as well as the heater control panel and the ECU.

 

[RonJ]

I've read that at one time, the Civic dome light shared a wiring circuit with the radio but I believe that was only '96-'98.

You are correct. This is only relevant to 96-98 not 99-00 Civics.

 

[5forfighting]

This car runs great in every way and the battery runs down when the car's been sitting for a couple of weeks....turns over very slow and *barely* starts. Had to jumpstart it once after it sat a couple weeks in cold weather. Not an issue if the car's driven regularly, but my daughter can go a week or two at college without needing to drive anywhere.

With the two fuses removed, the amp draw is only around 50ma, which makes me wonder...does anyone know what a *normal* parasitic drain rate would be on a stock car like this '99 hatchback, bone stock? Is this even documented anywhere?

 

[RonJ]

This car runs great in every way and the battery runs down when the car's been sitting for a couple of weeks....turns over very slow and *barely* starts. Had to jumpstart it once after it sat a couple weeks in cold weather. Not an issue if the car's driven regularly, but my daughter can go a week or two at college without needing to drive anywhere.

With the two fuses removed, the amp draw is only around 50ma, which makes me wonder...does anyone know what a *normal* parasitic drain rate would be on a stock car like this '99 hatchback, bone stock? Is this even documented anywhere?

Any of the components protected by fuse 43 and 47 are potential sources for the drain.

I don't know what normal drain is for a 99 Civic DX, but in general it should be no more than 25-50 mA. Your drain is clearly too high on both fuse circuits.

 

[5forfighting]

Thanks.

I buttoned up the car for the night and hooked the battery back up...as an afterthought, I set my multimeter to check for AC voltage and placed the probes across the battery. It read 27.5. I vaguely remembered this as a check for bad diodes in an alternator, which can also cause battery drain. Is this correct? The car was not running when I did this check, does it have to be running?

Thanks in advance.

 

[RonJ]

I buttoned up the car for the night and hooked the battery back up...as an afterthought, I set my multimeter to check for AC voltage and placed the probes across the battery. It read 27.5. I vaguely remembered this as a check for bad diodes in an alternator, which can also cause battery drain. Is this correct? The car was not running when I did this check, does it have to be running?

Because the engine was not running, there's no chance to produce AC voltage, so I don't think your test is meaningful. In addition, the alternator circuit has nothing to do with fuses 43 and 47. If you thought the alternator contributes to the drain, then test for DC drain with the alternator connector unplugged.