TB123A Terminal Block — What Part Fixes This Problem?

Understanding the Problem

Brief explanation: TB123A is commonly used as an internal identifier for a terminal block or wiring connector on appliances (dryers, ranges, ovens, some washers). A terminal block is the point where the incoming mains leads connect to the appliance wiring. When it fails it can cause loss of power, intermittent power, arcing, burning smell, or overheating at the back of the appliance. Diagnostic and repair steps: 1) Confirm what TB123A refers to on your appliance: check the appliance wiring diagram or the nameplate/model manual — TB or TB### often labels the terminal block on schematics. If unsure, take clear photos of the connector and model nameplate and look up parts by the appliance model number online. 2) Safety first: unplug the appliance (or shut off the circuit breaker for hardwired appliances). Wait a few minutes for capacitors to discharge. Use insulated tools and follow lockout/tagout if available. 3) Visual inspection: remove the rear access panel (or console access) to expose the terminal area. Look for melted plastic, black/brown scorch marks, cracked insulation, or discolored screws. Smell for burned insulation. 4) Check for loose connections: with power still off, try to gently wiggle each wire where it attaches to the block. Loose or corroded wire ends are common causes of heat and arcing. 5) Continuity test (power off): use a multimeter set to continuity/ohms to check continuity through the block where applicable (e.g., from incoming L1 to appliance L1 feed). A complete open where there should be continuity indicates a failed connector. 6) Voltage test (power on — use extreme caution): if you are comfortable and experienced, restore power and measure incoming mains at the terminal block (L1 to L2 for dryers/ranges or L to N for single-phase). Look for voltage drop under load — a high resistance connection will show significant voltage drop or heating. If you are not trained, stop here and call a pro. 7) Replace the terminal block if you find physical damage, no continuity, or heat-damaged screws/insulators. Replacement is preferred over repair when insulation or mounting points are compromised. 8) Replacement steps (general): a) Unplug appliance / shut off breaker. b) Photograph and/or label every wire on the terminal block (use masking tape + marker). Note screw positions and any jumpers. c) Loosen and remove mounting screws; carefully disconnect wires. If wires are pushed into a crimp connector that is damaged, you may need to trim back and re-strip the wire and install new crimp terminals or ring/spade connectors rated for the appliance. d) Install the new terminal block in the same orientation. Reattach wires to the exact corresponding terminals and tighten screws to the manufacturer-specified torque (hand-tight plus a small additional quarter-turn is common; do not overtighten to avoid crushing terminals). e) Reinstall access panels, restore power, and test appliance for normal operation. Re-check screws after a short period of operation to ensure no loosening or heating. How to fix (practical tips): - If the wire ends are corroded or the copper is frayed, cut back to clean copper and re-strip. Use properly sized ring or spade terminals crimped with the correct tool and heat-shrink where appropriate. - Replace any damaged lockwashers or mounting screws with OEM or equivalent stainless/heat-resistant hardware. - If the appliance is hardwired and the terminal block secures conduit or strain relief, ensure strain relief is reinstalled to prevent wire movement. Safety note: This part connects to mains voltage. If you are not comfortable working around live voltages or cannot positively identify wires and connections, hire a qualified appliance technician or electrician. Always disconnect power before touching wiring.

Common Symptoms

No power to the appliance, intermittent power/cycling, burning smell or scorch marks at the rear connection, visible melting of the terminal block, or appliance trips the breaker when plugged in.

Common Causes

• Loose or improperly tightened terminal screws causing high-resistance connections and heat
• Corroded or frayed wire ends or crimp terminals
• Physical damage or melted plastic from overheating or past arcing
• Incorrect replacement parts or improper installation lacking proper strain relief

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