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Radiator not getting hot? Here’s what to do

Don’t let a cool radiator get you down. We’ll help you troubleshoot the issue and talk you through what to do if it’s time to replace.

Don’t let a cool radiator get you down. We’ll help you troubleshoot the issue and talk you through what to do if it’s time to replace.

It’s freezing out, and your radiator won’t heat. Talk about a comfort nightmare. 

Cold homes in the winter aren’t just miserable to be in, they’ve also been known to increase respiratory health risks, so broken radiators are no small problem (1). 

Radiators work by using the heat from hot water or steam to warm the air around them. But there are a few roadblocks (both big and small) that can keep your radiators from working correctly. 

Let’s troubleshoot your radiator heating problem so you can get back to having a truly comfortable, cozy winter. 

In this article we’ll cover:

How to troubleshoot when your radiator won’t heat

Well-working radiators heat, of course. So if your radiator is running cold or lightly warm, there’s definitely a problem. But what’s the cause? 

Well, first off: Are all of your radiators not working—or just one? 

Check the radiators in your home with the heating system on and make sure each one of them is running hot. 

All checked? Cool.

Follow our troubleshooting guide accordingly:

One radiator not working

Are just one of your radiators acting up?

There are a few reasons only one of your radiators won’t heat—some issues you may be able to fix on your own, while others might require some professional help. 

  1. You have air pockets in the system.
  2. You have a radiator leak.
  3. There’s a radiator thermostat issue.
  4. There are blockages in your one radiator’s system.

Let’s dig in.

Reason #1: Air pockets in the system

If your radiator’s cold at the top and warm at the bottom, it’s likely an air pocket issue. When there’s a pocket of air in your radiator, air fills the space where hot water should go. This stops circulation in your radiator’s system.

The fix: Bleed your radiator

This odd problem has an odd-sounding fix: It’s time to “bleed your radiator,” which basically means releasing air that’s become trapped inside your radiator.

To bleed a radiator you’ll need to unscrew something called a bleed screw with a radiator key until you hear a hissing sound—that’s the air coming out! Keep going till you see water, then tighten the bleed screw and you’re good to go.

For a quick visual guide to bleeding a radiator, check out the video from Silverline Tools below.

Reason #2: Radiator leak

Radiators can leak at the hose, hose connections, or anywhere its parts are bolted to other pipes. The main cause of radiator leaks are corrosion or rusting in the radiator, but it can also leak due to poor maintenance or thermostat overheating problems. 

The fix for radiator leaks

Radiator leaks can be tricky to fix on your own.

The best way to know if your leak is a DIY project is… location, location, location.

The easier it is to locate and repair the radiator leak, the more likely it’ll be a DIY fix on your end.

Leaks near your thermostat valve pipe joint usually just need to be tightened up a bit: All you’ll need is a monkey wrench!

If your heating radiator in the home fails and leaks again, it can cause water damage, especially if there isn’t anybody home to notice it right away.

Now, sometimes a radiator leak is caused by rust and decay, which is a maintenance issue—and a full replacement may be needed.

The best way to know for sure is to have an HVAC pro come and take a look.

Reason #3: Radiator thermostat

Your radiator running cold might be a simple fix—your thermostatic valve is set incorrectly. A few things could cause this issue:

  • Your thermostat switched from a temperature setting to OFF. If this happened, all you have to do is switch your thermostatic radiator valve back to your preferred temperature. 
  • Your thermostat temperature is too high. This can cause your radiator valves to close. Check to see if your valves have closed. If they have, you can open them with your hand.
  • If you’ve tried opening your radiator valves and they won’t move, it may be time to call in an HVAC pro. When this happens, it’s called a seized valve, and it’s only fixed with a total valve replacement. 

Reason #4: Blockages within the system  

Remember how excess air in your radiator makes it cold up top and hot on the bottom? 

Well, trapped debris, a blockage, or sludge can have the opposite effect.

If the top of your radiator is hot to the touch but chilly down below, it usually means hot water can’t circulate due to build-up at the bottom of your radiator.

The fix for a blocked radiator

It’s time for a radiator power flush, friends! Power flushing gets rid of the debris and sludge that have built up over time in your radiators.

But before you put on your heavy-duty gloves, keep in mind that this is no small task and is usually best left to a professional.

More than one radiator not working

Are all your radiators not heating up in your house? Before we go any further, we’ve got a pro tip for you: Make sure your boiler switch and circuit breakers are set to ON! 

We know, we know, this sounds obvious.

Believe it or not, you wouldn’t be the first to assume your radiators are broken when all they needed was a power source.

Still not working? Here are some reasons why you might be having this issue.

  1. Boiler pressure
  2. Central heating controls
  3. Diverter valve fault
  4. Larger central heating and boiler issues

Reason #1: Boiler pressure

If your boiler doesn’t have enough pressure, it won’t be able to heat your house.

The fix for boiler pressure issues

To check your boiler pressure, look at the front of the boiler or the head of the cylinder, which is usually in the airing cupboard. 

If the pressure is too low, turn the top-up valve to increase it. And be careful!

You don’t want too much water to get into the system. Make sure to read your appliance manual to make sure you do this correctly.

Reason #2: Central heating controls

So your boiler seems to be working as it should, but your radiators still won’t turn on?  It’s a rare problem, but that doesn’t stop this wonky electrical issue from confusing your heating system.

The fix for a central heating control issue

Central heating control panels operate the timing and signals to your boiler. Make sure your timer is set correctly and choose the ON option to make sure your radiators get hot.

If you notice it’s not working or timing correctly, it’s time to call your trusted, handy-dandy HVAC technician. 

Tinkering with boilers too much can lead to even more problems and expenses. If your boiler isn’t getting the heat to your radiators, leave this part to someone who knows what they’re doing. 

Reason #3: Diverter valve fault

If your radiator controls aren’t working and you have a circulation problem, but your pressure is just fine, it might be a broken diverter valve. 

A diverter valve opens and closes to direct hot water to your heating system, but sometimes it gets stuck.

The fix for a radiator diverter valve issue

Sorry friends, this is a fix for the pros. It’s a complex system that takes a radiator expert to crack. And this may be a sign that you need an overall heating system replacement.

Trying to decide if it’s worth repairing or replacing your boiler? Give us a call. We can help. 

Reason #4: Larger central heating boiler and radiator issues

If all of your radiators don’t heat up instead of just one or two, this could be a sign of a bigger problem with your whole heating system.

And if your boiler heating system and radiators are older, it may just be time for an upgrade.

The fix for old radiator problems

Remember when we said we’d let you know when to replace your radiator? Well, this is it friends.

Sometimes, even after troubleshooting or calling an HVAC pro the best thing you can do is start fresh. 

But this fix is a pricey one.

Radiator replacements cost anywhere from $700 to $1,300 per unit on average (2). And replacing a whole heating system (if you use boilers and radiators to heat your home) and cost you up to $15,000! 

But you’ve got another option. Read on to learn about the best alternative to replacing your old heating system that keeps causing trouble.

illustrated image of old heating equipment vs new heat pump

The best upgrade for old radiators and boilers? A cold climate heat pump!  

When radiators hit the scene around the mid-1800s, they were a hot commodity.

Almost 200 years later? There are now more comfortable, more efficient, healthier, and safer home heating options.

Radiators are hot to the touch, many still run on gas or oil, and in some cases, boilers and radiators can be a fire or carbon-monoxide hazard. 

Older heating systems are pretty uncomfortable and waste tons of energy.

In fact, carbon boilers waste as much as 35% of their energy (through air leaks in attics and other escapes) compared to less than 10% from modern heating systems (3). 

Not to mention, natural gas and heating oil heating systems aren’t great for home indoor air quality. 

The good news? HVAC technology has come a long way since the Reconstruction Era. 

Allow us to introduce you to heat pumps.

They’re 3 times more energy efficient than traditional heating systems and make your home feel amazing (4).

81% say their home comfort has improved by replacing their fossil fuel heaters with heat pumps.

Cool Products 2022 consumer analysis

Don’t let the word heat fool you. Heat pumps keep your home warm in winter, but they also cool your home in the summer by moving indoor heat out.

(Learn how heat pumps work and why they’re the best way to heat an older home.) 

How are heat pumps better?

  • Heat pumps regulate uneven temperatures in your home instead of relying on one stream of airflow
  • They’re a great option for older homes and historic properties since there are options that don’t require ductwork
  • They’re multiple appliances in one: they cool your home in summer, heat it in winter, and dehumidify and filter the air year-round
  • Heat pumps warm and cool a home three times more efficiently than traditional HVAC systems
  • Heat pumps can run on clean electricity instead of fossil fuels

If you’re looking for a more comfortable, greener way to stay cozy in your home look no further than the Tesla of HVAC systemsLearn how to switch from an oil heat to an electric heat pump.

A few temporary fixes while you solve your radiator problem

The absolute worst effect when a radiator isn’t working is an overall, ice-cold house.  

Did you know blocking drafts in your home can help ward off some of your chills while you figure out what’s happening with your radiator?

In fact, air leakage can cause up to 40% of wasted HVAC energy

 Here are a few free and budget-friendly ideas. 

  • Get creative and rearrange your furniture! It may sound silly, but there’s a method to our madness. Moving your furniture away from your radiators and vents helps unblock imbalanced or disrupted heat flow in your house. Plus, it doesn’t cost a thing! (Learn more ways to fix a draft house.) 
  • Opt for door sweeps to help block unwanted air coming from your doorways. 
  • Invest in thermal curtains. Thermal drapes are a great temporary remedy for uneven temperature and drafty rooms, and they can even help against energy waste. While you’re at it, check out our thermal curtain guide.

If you’re absolutely freezing in your own house right now, read How to stay warm in a cold house to get 21 quick tips to warm up fast.

Finally, a great way to keep warmth in your home in the winter and optimize the heating system you already have is to properly weatherize your home.

Check out our air sealing and insulation guides to find out how to get rid of uneven temperatures and have comfortable home year round

5 energy efficiency myths FREE ebook animated gif

Ready to make your house super comfortable and cut energy waste?

Check out our FREE home energy-efficiency guide to learn how 3 core efficiency upgrades can make your home more comfortable year-round.

And, you know, keep the heat you’re paying for inside your house.

Get the guide

Frequently asked questions

Still have questions? Check out common ones about radiators not working below.

Don’t see your question here but having trouble keeping your house warm?

Call us at 917-905-3788. We’re the home comfort and performance experts—and we can help get your house back on the right track.

Why is the radiator not getting hot?

If your radiator is running cool or warm instead of hot, the first thing you can do is find out if it’s just one or several radiators causing you trouble—then go from there. Tap here to get a list of troubleshooting options.

What do you do when one radiator is cold?

When one radiator is running cold, there’s definitely a problem. The first step is to troubleshoot. You might need to bleed the radiator or schedule a power flush with an HVAC pro. Tap here to see more tips for when one radiator’s not working.

Why does my radiator not get hot after bleeding?

If your radiator still doesn’t get hot after you bleed it, you have a bigger heating system issue that needs the help of an HVAC pro, or you’re in need of a radiator replacement. That can cost you anywhere from $700 to $7000 bucks, depending on the number of radiators you need fixed.

How do I get my radiator to work?

There are a few ways to troubleshoot a radiator that’s running cold. Tap here to be guided through step by step. Once you’ve done some troubleshooting, you may be able to do a quick fix on your own, or you may need to reach out to a contractor for help. 

Should you bleed radiators with heating on or off?

Always make sure your heat is off before you get started on any radiator tune-ups. Check your manual to determine if there are any other safety issues to keep in mind. 

Why are all my radiators hot except one?

Sometimes it’s one, sometimes it’s more, but it’s very possible for a single one of your radiators to act up. It may even be as simple as a wrong thermostat settings (which has a few quick fixes).

Replace your old heating system for good — at no upfront cost

It’s as easy as a 2-minute quiz.

Finally say goodbye to your vintage heating system that’s on its last leg and hello to modern, energy-efficient heat pumps. 

If your house qualifies to work with Sealed, you can get customized heat pump HVAC, high-performance insulation, and professional weatherization upgrades to your home at no (or very little) upfront cost.

We’ll do all the heavy lifting to make your house feel great. And we take all the guesswork out of finding trusted and vetted local professionals.

We’ll negotiate the price, manage the project, and make sure everything goes as planned. Take the quiz to see if your house is eligible.

November 18, 2022