Why is one radiator not heating up when others are fine?

Diagnosing a Single Cold Radiator

When just one radiator isn't heating while others work fine, the problem is localised to that radiator or its valves.

Common Causes

1. Stuck Thermostatic Radiator Valve (TRV)

The most common cause - the pin inside the TRV can seize:

• Remove the TRV head (usually unscrews or lifts off)
• Check if the pin moves freely up and down
• If stuck, gently tap with a hammer handle or spray with WD-40
• Work the pin up and down until it moves freely
• Replace the TRV head and turn to maximum

2. Lockshield Valve Closed

The small valve at the other end controls flow rate:

• Remove the plastic cap
• Use pliers or an adjustable spanner to open it
• Turn anti-clockwise to open (usually 1-2 full turns)

3. Air Lock

Air trapped in this specific radiator:

• Bleed the radiator using a radiator key
• Listen for hissing air escaping
• Close valve when water appears

4. Localised Sludge Blockage

If above steps don't work, sludge may be blocking flow:

• Radiator may need removing and flushing
• Consider a system powerflush
• Professional diagnosis recommended

Quick Diagnostic

• Both pipes cold = Flow problem (blocked or valve closed)
• One pipe hot, one cold = Blockage inside radiator
• Both pipes hot, radiator cold = Severe internal blockage

When to Call Us

• TRV pin is completely stuck
• Radiator needs removing to flush
• Problem persists after trying above steps
• Multiple radiators affected

NK Gas Services can diagnose and fix radiator problems same-day. Call 07404 922458 for Wolverhampton, Walsall, and Cannock areas.