How to change the battery in Brio's mighty red action locomotive train!

'Triangle Screws' are security screws so that you can't remove them. Your question is a bit to specialised for Fixya, so contact the maker direct. They may just say, "send it back and we will replace it, or repair it".

33592 Mighty Red Action Locomotive ' BRIO World Toy Trains

www.brio.us > railway > trains-wagon-and-vehicles > m...

Classic BRIO design: This durable, retro designed toy allows your child's imagination to flow and helps improve their fine motor skills and spatial awareness.

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I had the same problem with one old locomotive. There are three things to check:

1. the main power slide switch is set on the rigth position
2. on the bottom of the loco, there a small red bump, it is perhaps blocked in the pushed position
3. this one was the solution for me. Dismantle the battery cap and make sure that both metallical parts are in contact.

Here's the link to BRIO Customer Service, contact them for instructions.
Customer service BRIO

See my comment in this answer: Changed batteries in Brio train mighty red locomotive and still does not...

They are two AAA micro batteries.
Insert a cross-tipped screwdriver into the funnel of the engine, unscrew completely and the black nose comes off, revealing the batteries.

Look in to the funnel. Unscrew and the front comes off and then replace it...

Look for and remove little cross headed (not triangular) screw.

Hi Tarja, your question is 4 years old, but here is the answer:
You've probably seen the odd shaped tiny screws on the underside of the train. Ignore them - they require specialized tools and only lead to the wheels and gears.
You just need to insert a small cross-tip screwdriver into the exhaust funnel of the engine and remove the screw completely. The black front of the engine comes off and reveals AAA micro batteries which you gently shake out of the engine and replace.
As ever so often - once you know how to do it, it is very easy.
And - no, I didn't find out myself either *grin*

The battery is easy to replace. The screw is located in the black "smokestack" and will require a small size phillips-head screwdriver to unscrew. The rest is easy--lift up on the black smokestack (I usually leave the screw in place), and the two AA batteries are located end-to-end in the body.

Easy to do. You'll find a small phillips screw located at the bottom of the black smokestack. After unscrewing it, lift up the entire front black part and you will see two AA batteries inside the body of the locomotive. Careful not to strip the screw when replacing the black smokestack part, as it is the only thing holding it down!