My advice is to hire an electrician. I, like you, am a do it yourself type person, but you have to know when to call an expert. They have the correct tools to follow the circuits and to verify they are wired correctly and that there is no damage to the wires inside the walls. I work for an electrical distributor and hear horror stories from electricians all the time about having to correct something someone did wrong or even worse to rewire after a fire. Unless you did the original wiring yourself, you have no way of knowing without testing that things were done right by the last person. Err on the side of caution, get a professional.
Hubby is an electrician and suggests you see what voltage is marked on the heaters as they may be 220v and not 120v . In the older homes they used a black and a white as 220. for baseboards which is 2 hots, and therefore it won't work on a 120v receptacle as you need a neutral.
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