you go to ecruteak city and a man gives it to you there
In a house that's in Ecruteak City.
At Seafoam islands. Use dowsing MCHN
In Ecruteak city in the house right of the Pokemon gym
There are 3 hidden in the game, you can only find them with dowsing machines
In Ecruteak City. Go to the house in the middle of the gym and the Pokemon Center. Talk to the character standing at the table and answer yes to his questions. He'll give you the Dowsing MCHN.
There's one in Route 34, Violet City, and Ecruteak (Dowsing Machine.).
Use the dowsing machine on Cinnabar Island, you may need the HM Rock Climb to get to it. I believe there is also an Electirizer there.
You can find a rare candy in heartgold in... Johto: Route 34, Violet City, Ecruteak City (With Dowsing MCHN), Olivine City (With Dowsing MCHN), Radio Tower (Earn 25 Points at Buena's Password), Mt. Mortar (With Dowsing MCHN), Mt. Mortar, Tin Tower, Whirl Islands (With Dowsing MCHN), Whirl Islands (With Dowsing MCHN), Mt. Silver (With Dowsing MCHN), Shining Lighthouse Kanto: Route 27, Route 28 (With Dowsing MCHN), Vermillion City (Fan Club President), Cinnabar Island (With Dowsing MCHN), Indigo Plateau (With Dowsing MCHN), Cerulean Cave (With Dowsing MCHN), Victory Road Shop: Johto: Battle Frontier, Pokeathlon Dome Pokéwalker: Sinnoh Field (5000+ Steps), Sightseeing (5000+ Steps) . I think that's everything.
The dowsing machine is on the pokewalker.
Max Revives: Route 44, Ruins of Alph, Radio Tower (Goldenrod Loterry Ptize), Mt. Mortar (On ground and Dowsing MCHN), Tin Tower, Dark Cave (Dowsing MCHN), Whirl Islands, Mt. Silver (Dowsing MCHN), Lake of Rage, Pewter City (Dowsing MCHN), Diglett's Cave (Dowsing MCHN), Mt. Moon (Dowsing MCHN), Cerlean Cave (On ground and Dowsing MCHN), Seafoam Islands (Dowsing MCHN), and Victory Road (On ground and Dowsing MCHN).Rare Candy: Route 34, Violet City, Ecruteak City (Dowsing MCHN), Olivine City (Dowsing MCHN), Radio Tower (Earn 25 Points), Mt. Mortar (On ground and Dowsing MCHN), Tin Tower, Whirl Islands (Dowsing MCHN), Mt. Silver (Dowsing MCHN), Shining Lighthouse, Route 27, Route 28 (Dowsing MCHN), Vermilion City (Fan Club President), Cinnabar Island (Dowsing MCHN), Indigo Plateau (Dowsing MCHN), Cerulean Cave (Dowsing MCHN), and Victory Road.
It's called the dowsing machine in SoulSilver and HeartGold, you get it from either Ethan/Lyra, or someone you have to do a job for. I can't remember which, I know you have to beat the goldenrod Gym first.
In any random place.Sometimes u need the dowsing machine.Sometimes in the Pokeathalon they are prizes for like 2000 points. You could cheat and get lots, but then again that's cheating.