TB123B Terminal Block — What It Fixes and How to Replace It

Understanding the Problem

Brief explanation: TB123B is commonly used as a terminal block (wire connector/terminal strip) in many household appliances to connect the incoming power cord to internal wiring — especially on ranges, dryers, ovens and some washers. When the terminal block fails it can interrupt power or cause intermittent power, arcing, burning smells, or visible heat damage. Step-by-step diagnostic & repair steps: 1) Confirm the part and appliance: Verify TB123B is the terminal block listed for your appliance model (check the model number and OEM parts list). The physical part is usually at the rear where the power cord enters the appliance. 2) Safety first: Turn OFF power at the breaker or unplug the appliance. Use a non-contact voltage tester to confirm there is no live voltage present before touching wires. 3) Visual inspection: Remove the access panel to expose the terminal block. Look for melted plastic, brown/black discoloration, loose or burnt terminals, frayed wires, or a loose cord clamp/strain relief. 4) Photograph wiring: Take clear photos of wire locations and colors so you can re-attach exactly the same way. 5) Continuity and short tests with a multimeter: - Set meter to continuity or lowest ohms range. - Check continuity between the incoming power terminal and the corresponding outgoing terminal (should show near 0 ohms if intact). - Check for shorts to ground: there should be no continuity between hot terminals and chassis ground. - If the block is cracked/open you’ll see no continuity where there should be continuity. 6) Confirm symptoms tied to terminal block: - If appliance has no power or only intermittent power to a heater/motor and the block shows burn/damage or fails continuity, the block is the likely fault. - If block looks good and continuity is OK, continue testing the cord, fuses/thermal cutouts, heating element, motor or control board as applicable. 7) Replace the terminal block (if failed): - Remove any cord clamp/strain relief, loosen and remove screws holding wires, and remove mounting screws holding the terminal block in place. - Install the new TB123B in same orientation. Reattach wires to the exact terminals (use your photos). Tighten screw terminals securely — snug but don’t over-torque and strip the screw. - Refit the cord clamp/strain relief to prevent movement and wire chafing. - Reinstall access panel. 8) Restore power and test: Turn the breaker or plug back in, run the appliance briefly and watch/listen for arcing, burning smell, or loose connections. Re-check tightness if any issues. 9) If problem persists: If the terminal block replacement does not fix the symptom, test the incoming power cord, main fuses/thermal cutouts, heating element, motor, and control board. A burnt terminal block can be a symptom of an underlying overload or short elsewhere — rule that out. Safety note: Always disconnect power at the breaker or unplug the appliance before diagnosing or replacing electrical parts. Use insulated tools and a voltage tester to verify power is off. If you are not confident working with mains electricity, hire a qualified appliance technician.

Common Symptoms

No power to appliance or to heating element/motor, intermittent power or cycling, visible burning or melted plastic at cable entry, sparking/arcing at the terminal strip, burning smell near the cord entry.

Common Causes

• Loose or under-tightened screw connections causing arcing and heat
• Corrosion or moisture leading to high-resistance connections
• Overload or short circuit that burned the terminal block
• Physical damage from poor strain relief or cable movement

Popular Parts That Fix This Problem

These are the most common replacement parts that fix this problem. When you're ready to order, click below to find the right part at ProsourceParts.com — just search by your appliance model number for a guaranteed fit.

Frequently Asked Questions