Do two wall controls mean there are two separate heaters?
Not necessarily. They may control separate equipment or parts of one system. Use the actual setup and records; do not guess from the number of displays.
Record the symptom
Give each control a location name and list the rooms associated with it, if known. Record the displayed room reading and target separately. Describe any response already observed when the normal schedule called for heat.
If a room addition has its own control, say whether the space was ever heated satisfactorily. A longstanding comfort problem and a new loss of response may need different findings. Avoid adjusting installer settings to make one control resemble the other.
Plan the access
If rooms were changed, gather the plans, old invoices or label photos you already have. They can help show which system serves the space. Keep walls and hidden spaces closed.
If you are unsure about past permits, give the address to the building office. The county has a process for work done without required permits. That does not mean your home has a violation.
Define the repair decision
Ask whether the request reaches the correct system or zone and whether the control setup matches it. First confirm that the system serves that room. A new wall control cannot fix an unrelated unit.
Confirm whether a plan affects one control, a zone device or the equipment itself. Have every person who approves the shared system changes understand that scope before work begins.
Questions about this repair
Should I set both controls identically for diagnosis?
Record their normal intended settings instead. The proper relationship depends on the installed system and should be established during check.