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Garmin III Plus powers up on car adapter but not on batteries

Older GPS III Plus been working fine fo years. Over winter AA (4) batteries died while unit was idle. Replaced batteries, unit did not power up. My immediate thought was the internal memory battery needed to be replaced. However, plugged in unit to power adapter in car and unit powered up fine. All waypoints and routes were intact.

Could the internal coin battery be the issue even though unit powers up on car adapter ?

Thx for any and all help.



  • morrisrh 0 Points
    No replies yet to my question, but I'll post below what I did to close the loop on the question. Probably not a lot of users for these specific units anymore but may be useful to others in a generic sense.

    In summary, I replaced the internal battery and reassembled the unit. It now works on both AA batteries and car power. Some things I found:

    The battery springs in the compartment for the AA batteries were not corroded by old battery leakage. So I discounted that as the problem.

    Some documentation I saw on the internal battery refer to the internal battery as VL1220/VCN. Which is soldered directly to circuit board using the tangs connected to the battery. I ordered a couple from Mouser. When I cracked the case, however, I found the internal battery was a BR2032/VBN, attached to the inside of the case with 2 sided tape and 2 wires soldered to both the battery tangs and circuit board. I ordered that battery from Mouser. I desoldered the old battery, soldered in the wires for the new battery and reassembled.

    Connected unit via serial port to my computer and to a 12V power source. Powered up unit. First made sure the version was still the most current (2.06) and it was. I had to apply the GPSEOW fix again to get the unit to pick up the correct date from the satellite (post Y2K issue for old units), that also worked, and date was correct. Apparently, this fix is used in internal memory and not to the ROM firmware itself. So I guess I will have to apply every time the internal battery goes bad. From MapSource, then downloaded my backed up 300 waypoints and 20 routes from the PC to the GPS. All reloaded fine. Then disconnected the unit, powered off, put in 4 AA batteries, and unit powered up on it's own. So success. Now works on both external AA batteries and 12V power in the car. Rick
  • Boyd 1985 Points
    Thanks for taking the time to follow up Rick! :)
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