How to diagnose 18v Ryobi mower that won't start?

noelt

Hi, I have a Ryobi mower model number OLM1840BL, last time I used it, finished mowing and put it away. Got it out this time and it won’t go. Batteries are fully charged and all contacts are clean. Press the centre button and pull the leaver, 4 green lights come on then flashes red.

EricL

Hello @noelt

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your Ryobi mower.

That’s always frustrating when something was working perfectly last time and then suddenly refuses to cooperate.

On the Ryobi OLM1840BL, four green lights followed by a flashing red light usually means the mower’s protection system is stopping it from running. Even if the batteries show full charge, the mower may be detecting an overload, a motor issue, or a safety interlock problem.

The first thing I’d suggest is checking underneath the deck. Make sure there’s absolutely no grass build up packed around the blade or wedged between the blade and the housing. Even dried grass can cause enough resistance for the mower to trigger protection mode. With the battery removed, carefully tip it on its side and spin the blade by hand. It should rotate freely without grinding or feeling stiff.

Next, double check the safety systems. Make sure the handle is fully locked into position, as these mowers have a handle safety switch that prevents startup if it’s not properly engaged. Also confirm the catcher is seated correctly. If either of those switches isn’t fully engaged, it can cause the red flashing fault.

It’s also worth trying one battery at a time if you have two installed. Occasionally one battery can show fully charged but still fault under load. Insert just one battery, try starting, then swap and test the other.

If the blade spins freely, the safety switches are properly engaged, and both batteries behave the same way, the flashing red light may indicate a motor or controller fault. In that case it’s likely an internal issue rather than something simple you can reset. Sometimes leaving the batteries out for ten minutes can reset the control board, but if it still flashes red after that, it may need servicing.

How old is the mower? If it’s within the warranty period, Ryobi is usually pretty good with repairs or replacement. Please makes sure to bring your docket or proof of purchase should you decide to bring the mower to the store.

If you need further assistance, please let us know.

Eric