Garmin Forerunner 305 Battery Charging Failure – Solved!

I’ve had my Garmin Forerunner 305 sports GPS for nearly three years now and it’s logged several thousand km of running and cycling. Up until recently it worked pretty flawlessly, but during my recent training tour to Sweden, during a particularly wet and physical run, I noticed it kept switching off. Further investigation revealed that, on tapping the unit, it would switch off. Jumping down various ledges in the tough Swedish terrain was presumably having the same effect. For subsequent runs, it refused to switch on at all, even when doing a soft reset (holding down Mode+Reset and then powering up) or a hard reset (holding down Mode+Enter while switching on).

While being plugged into the charger, the unit would operate fine – although when charging, the “Charging in Progress” would always switch to “Charging Complete” after around five seconds, and on unplugging the charger, the unit would switch off immediately, indicating the battery was completely uncharged.

Scanning various web forums talking about such issues, the soft or hard resets, or a firmware software downgrade/upgrade, were the standard fixes – having tried all of these, it looked like my only solution would be sending the unit back to Garmin for an out-of-warrenty replacement. Apparently, some forums said, they are willing to do this for free, with a quick turnaround, due to a “known manufacturing fault”.

I need my Garmin fixed for Thursday, when it has to navigate me 1000km from Land’s End back to London, so that return-to-manufacturer wasn’t an option. Thankfully, I was able to solve the problem with a little prodding around inside the case.

The Forerunner 305 case is pretty easy to open up, as there are no screws for clips holding the front and the back together – just some weak glue. Prising the two parts apart with a small kitchen knife was straightfoward to do, and on examining the interior, the problem was obvious.

There are eight brass pins on the inside back part of the unit, on the other side of the case from the four charging/communicating contacts that connect to the docking station. The pins are bent back on themselves to provide a hinge to the corresponding eights contacts on the inside front part. The left-most metal pin was completely corroded and had gone green, presumably due to an electrolysis reaction with some water or sweat that had got in the case. Not all of the eight pins are connected to the four charging contacts – the affected one wasn’t, which was why communication with the docking station was working fine. However, this was presumably one that was connected to the battery, which was why the battery was unable to charge.

On touching the corroded pin, the raised section immediately came apart (not good.) After cleaning the gunk away with a pencil eraser, I used the kitchen knife to gently prize the remaining slab under the pin upwards, and bent it back on itself, so that it formed a new, shorter pin. I then put the case back together, joining the two halves with sellotape (for now – I need some silicon glue to make a good fit) and the unit now started charging normally, and appears to work fine.

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20 Comments

  1. Stumbled across this trying to see if my 305 is able to charge whilst the unit is being used, and I have to say that it made an entertaining read … Having performed the same “operation” on various HR devices (Sigma Onyx Easy being the most recent one) I am glad I’m not alone in the world of duff seals, ingenuity and fettling.

    Cheers, and happy runs,

    Al.

  2. Cheers for this! I’m experiencing exactly the same issue – especially the tapping on the screen to switch it off! I’m not sure if I’m going to open it up yet as I can usually dismantle, but i’m good at the “dis” and not so good on the “mantling” part…

    On a side note – it was freaky finding your blog as you’ve got exactly the same WP theme as i have – looking good!

  3. I tried doing this as well but can’t seem to open up the watch? I’ve ran a knife inside to kill as much of the glue but just can’t open the unit… any help?

  4. Exactly the same problem, TWICE now. The first time the face fell off all by itself and Taiwan Garmin replaced the whole unit for US$80 or so. Now, a year later, after merely being exposed to rain and sweat, it has packed up AGAIN. This time they need ANOTHER US$80 to repair/replace it. When the unit is “submersible to one meter for up to 30 minutes”, this is UNACCEPTABLE and I am very pissed off!
    I have carried out your procedure and unfortunately there is nothing left at all of pin number 8. Has anyone out there convinced Garmin to replace FREE OF CHARGE, as they obviously should, along with a warning that the units are NOT water resistant AT ALL?

  5. I phone Garmin to get my battery replaced. They said to send it in to them and they would send me a brand new Forerunner 305. They turned it around in 4 days and it cost £58. That’s £58 for a brand new device – amazing.

  6. I have. 110 watch 15 mths old , it won’t work at all , They want £44 for to replace it , Any have one had better luck with them

  7. Ollie, just a quick thank you for this…… having had my Garmin 305 for over 6 years, I thought it had finally run it’s last race. The symptoms were as described above, so I had nothing to lose by prising the watch open with a ‘Stanley’ blade. I was presented with exactly the same corroded pin on the left, which crumbled when touched. I was able to gently bend what remained of the pin upwards to make contact again with the (inside) face of the watch. I then reassembled and placed in the charging cradle (held the lot together with an elastic band) to be sure the contacts were indeed touching…….. and hey presto !, fully charged in the morning and picking up a signal in seconds. Job done, thanks again.

    1. Good to know! I’m on my second one now, but it is doing just fine.

  8. Thank you so much for your suggestions. I had the EXACT same problem with my Garmin Forerunner 305 – charging in progress, quickly followed by charging complete. When I took it off the cradle, it wouldn’t power up. Garmin support said the watch was at the end of its life and they could not fix it. Interestingly, the support person never had me do any of the reset steps I’ve seen on the internet. After trying all of the reset options I could find, without success, I came across your post and decided to give your suggestions a try. Just as you said, the watch pried open easily. The pins were corroded and in trying to gently clean them, the pin furthest to the left broke in half. I carefully bent the pin up, just as you did, put the watch back together and it worked! I glued the watch together and let it dry for about 5 days. Today was the first day I took the watch out running and it worked perfectly! Let’s hope it has some more life in it. Thank you again, especially for your detailed instructions. I really appreciate it.

  9. You’re a bloody legend. Initially bought a new battery but then still did the same. About to give up but love my 305. Exactly the same problem. Thank you!

    Dom

  10. In my case the left most pin on the back of the front (when looking at the back of the front) was very frail and flattened down relative to the other pins. I gently bent it up, put the front and back back together and it’s now charging properly. Thanks a bunch.

  11. Found this when searching for a solution for my broken GPS, I took my Garmin 305 apart and found the two outer pins were broken. I followed your lead and lifted the contacts and bent them over to the same height as the other connections. I then reassembled the two halves of the case and held them together with some electrical tape,turned on and everything works perfectly. Great advice thank you.

  12. Thank you for this, after 8 years of service I thought my Garmin 305 had died, but found this article, took it apart and found the exact same thing. Scraped off the corrosion, the broken pin fell off so I bent the remaining bit up, put it back together and it’s as good as new! Thank you so much!

  13. Thank you for this great article. Had exact same problem with my 305 after a long day in constant rain during a 50 mile race. A couple of days later it would only power on in charging cradle. Did exactly as here, opened case, found broken pin, bent it up– now works perfect

  14. I parted company with my Garmin 305 today, or rather it parted company with me. I glanced at my watch while out running and to my horror I was just looking at a strap and battery, the face having fallen off some where along route. It looks like the whole module has gone as people have described re removing it. I wasn’t able to find where I had parted company and it looks like I will need a new watch.

  15. Had the same issue, and followed the same procedure described. I was so shocked by how easily it was for me to dismantle this watch!! Inside I found a pin that was almost fell off. Then, I did what the post said, closed it again (although the two parts dont hold on together), turned the unit on, and it worked!! now I need to find some kind of glue that seals the watch… silicon perhaps…

  16. I replaced my battery (thinking it was defective) and came up with this symptom. My pin was so corroded that it did not look like a pin. After scraping it under a lighted magnifier, I tried to bend it as described. It would not make contact. The pin ended up breaking off. I was able to take a razor and literally chop off that portion of the connector, and get a solder dob on the little pad on the board. Then solder a jumper wire to both terminations. It took a few tries, I almost threw it in the trash. Looks like I got it, waiting 12 hours for the glue to cure.

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