LB3500 will not turn on

[shermbb]

My 2.5 year old LB3500 will not turn on.  I have unplugged/plugged most, if not all, of the connectors.  The batteries read approximately 25 volts.  Vishal replaced the charger earlier this summer.  I don't recall the voltage reading for the charger, but I want to say that it was around 29 volts.

Does anyone have any suggestions for a next step for diagnosis?


I love the mower when it is working, which has unfortunately been a very small percentage of this summer.  I really must wonder if the mower is worth the continued investment after the warranty expired.

problems over the past 2 years:  2 bad blade motors, worn out front wheels, bad power supply, bad signal booster, frequent "no signal" errors, occasional "blackout" errors (even though the base includes a battery backup UPS).

[RobotLady]

I'm very sorry to hear about the trouble you have been having.

You should use the ohming feature of your multimeter to trace the connections from the recharging bolts to the motherboard.  Also make sure the bolts are making good contact with the plates.  I can tell you more, but I would have to charge a reasonable fee for the use of my time.

You can also try contacting KA directly.

[toolbelt]

Does it turn on if it's in the charger unit? If so then you most likely need a new battery.  Out of the charger the display is dead and you get zero response.  I just went through this and after installing the new battery it worked like new.  The voltage also read around 25 volts.  When in the charger unit it would read 29 volts (measuring at the charger nuts).  Hope that helps.

[mafster69]

I had this behavior. In my case, it turned out to be one of the fuses on the motherboard.

[RobotLady]

Right, I forgot about the fuses.  You definitely should check them first.

[shermbb]

I forgot to mention that I checked the two fuses on the circuit board, and they are fine.  Also, the mower will not turn on in the charging station either...

I can try to track down the voltage through the circuit board, but my gut tells me that the mother board is probably bad.  If this is the case, I'll likely decide next year if the mower is decommissioned.  My current thoughts are that the mower is not reliable enough to justify the continued expense.  As I have read in this board and others, the mower is great - but only when it is working.  Along this line of thought, I'm trying to think of any other appliances that have this kind of failure rate or poor uptime rates, and I'm drawing a blank....which happens to be the same response as the display on my mower.

[shermbb]

Make that 3 fuses

[prb238]

I had a similar issue several months ago with my robot. I checked all the fuses and they appeared to be ok. I then sent it in to Robotlady to have it checked out. I was very concerned that it was the motherboard. Well, it turned out after all to be just a fuse. I guess even though they all looked visibly ok, there was one that was bad.

If you haven't tried yet, I'd suggest replacing all the fuses even if they look ok. Pretty cheap to do and may save you from shipping it in if that turns out to be the issue.

[RobotLady]

Note, 25 Volts is not high enough.  It sounds like the battery is not getting charged properly.  Check the voltage on the plates.  Plug in the winter charger and check the voltage on the terminals that connect to the battery.  Should be 29.3V.  I don't think the battery is bad or you wouldn't get 25V.  That sounds like the voltage it stopped working at.

There are 3 fuses on the motherboard.  One is under a cover you have to carefully take off.  The other two are visible.  Check them all...