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Thread: huge 3.5A Parasitic battery drain, fuse test did not locate the issue

  1. #1
    DX User
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    Jun 2016
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    1989 Honda accord LX
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    huge 3.5A Parasitic battery drain, fuse test did not locate the issue

    Good evening folks. Working on the old 1989 LX accord again.

    Car drives fine when jumped, but battery has been going flat after a short time not driving.

    I will give a short history if it helps: When I first obtained this car about two years ago, there was a parasitic drain already. I did the standard ammeter test and found that the problem circuit was the hazard lights, so I just pulled that fuse and this problem has not come up again until now. About a year ago, a coolant hose above the alternator leaked and shorted out the main alternator wire and blew a fuse. I replaced the fuse and alternator after that, but the battery light has been sporadically on while driving ever since, even when there is good charging voltage. I have actually replaced the alternator in the car three times total since then, as the reman ones seem to die often. The same random battery light remains. Last replacement was about three months ago, and things have been running ok since then. Currently alternator gives good 14+ volts charging.

    Now for troubleshooting the drain, I disconnected the (likely well worn by now) battery and ran the test using the battery from another car which was healthy. With doors closed, Key off, all lights/etc off, I started reading 3.8A drain, which over time slowly lowered on its own to ~3.5A, clearly this is a huge short. I had someone monitor the meter and pulled each fuse on the driver side inside and the passenger side engine bay blocks. The only one which changed anything significantly was the 'Battery' one under 'Main Fuse' - current dropped to zero, but obviously this does not give any useful information except that maybe the problem is not with the starter / alternator. (I manually checked these too by removing the main post wires - they were not the cause of the drain) There was no obvious damage / degradation of insulation on the positive / negative cables, which was the last thing I could think to check offhand.

    Are there any other electrical connections on these cars which do not go through the fuse block to look at? Any other possibilities?

    Thanks much!



  2. #2

    Dr_Snooz's Avatar
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    1989 Accord LX-i
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    Re: huge 3.5A Parasitic battery drain, fuse test did not locate the issue

    Try doing a search on here for "choke heater short". If you have a coupe, unplug the seat belts in the doors.
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


    1989 Honda Accord LX-i Coupe, 240k miles, MT swap, rear disc swap

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  3. #3
    SEi User Hauntd ca3's Avatar
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    Re: huge 3.5A Parasitic battery drain, fuse test did not locate the issue

    Put a fresh battery in it and check the charging under load .
    Any less than 13.5v under full load at 2000 rpm suggests a failing rectifier .
    A failing diode in the rectifier can cause them to draw rotor current which is approx 3.5 - 4 amps .
    You could also disconnect the battery cable and regulator plug from the alternator and see if the draw goes away .

  4. #4


    Join Date
    Nov 2004
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    88 LXi
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    Knoxville TN
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    Re: huge 3.5A Parasitic battery drain, fuse test did not locate the issue

    Seat belt retractors is one load if there stuck.

    Diode in the alt can like haunted said.

    Headlight motors.

    if you search around there a couple others
    1988 Lxi owner since August 1995
    336k miles running strong!
    Now running E85.

    Oldblueaccord <<< MY YOUTUBE PAGE!

  5. #5
    DX User
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    May 2023
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    1989 Honda Accord LXi
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    Mexico
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    1

    Re: huge 3.5A Parasitic battery drain, fuse test did not locate the issue

    Found a solution?
    I have a similar problem, replaced the alt a couple times already, as well as the battery, I tested for drain and it did have, after removing the headlight retractor fuse the drain went away, but the battery would still be drained after a couple hours.
    Also I'd like to know If the rectifier is the same as the regulator which is on the alternator itself, if not, I think I found my problem cuz I've never replaced the rectifier (idk where it is located).

  6. #6

    ShiRen's Avatar
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    May 2018
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    MO
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    Re: huge 3.5A Parasitic battery drain, fuse test did not locate the issue

    Yes it is. It would have been replaced if you didn't have to swap parts on your new alternator

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