{"id":689,"date":"2021-01-18T11:00:58","date_gmt":"2021-01-18T16:00:58","guid":{"rendered":"https:\/\/www.premierhvacpa.com\/blog\/?p=689"},"modified":"2026-09-21T11:37:32","modified_gmt":"2026-09-21T15:37:32","slug":"when-furnace-blows-cold-air-troubleshooting-heater","status":"publish","type":"post","link":"https:\/\/www.premierhvacpa.com\/blog\/when-furnace-blows-cold-air-troubleshooting-heater\/","title":{"rendered":"When a Furnace Blows Cold Air: Troubleshooting Your Heater"},"content":{"rendered":"<div class=\"wp-block-image\">\n<figure class=\"alignright\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"219\" src=\"https:\/\/www.premierhvacpa.com\/blog\/wp-content\/uploads\/2021\/01\/When-a-Furnace-Blows-Cold-Air-Troubleshooting-Your-Heater-300x219.jpg\" alt=\"Woman wrapped in a blanket warming her hands in a cold home needing heating repair.\" class=\"wp-image-692\" srcset=\"https:\/\/www.premierhvacpa.com\/blog\/wp-content\/uploads\/2021\/01\/When-a-Furnace-Blows-Cold-Air-Troubleshooting-Your-Heater-300x219.jpg 300w, https:\/\/www.premierhvacpa.com\/blog\/wp-content\/uploads\/2021\/01\/When-a-Furnace-Blows-Cold-Air-Troubleshooting-Your-Heater-768x562.jpg 768w, https:\/\/www.premierhvacpa.com\/blog\/wp-content\/uploads\/2021\/01\/When-a-Furnace-Blows-Cold-Air-Troubleshooting-Your-Heater.jpg 800w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/figure><\/div>\n\n\n<p>It\u2019s time to re-explore an issue that we get called about a lot during this time of the year\u2014a furnace that\u2019s blowing cold air. This is of course a very unsettling problem and not one that you want to face. When your furnace suddenly starts blowing out cold or lukewarm air from the vents, it\u2019s easy to panic. But before you do, check out our advice below. <\/p>\n\n\n\n<p>The thing is, there are a number of reasons that a furnace may experience this problem. Some of them amount to nothing more than \u201cuser error\u201d while others are of course more serious and will require a professional to fix. Read on to determine which is the case for you. <\/p>\n\n\n\n<!--more-->\n\n\n\n<h2 class=\"wp-block-heading\">When Should You Call for Furnace Repair if Your Heater Blows Cold Air?<\/h2>\n\n\n\n<p>A furnace blowing cold or lukewarm air does not always mean the system has failed, but persistent problems may require professional furnace repair. Common causes include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Incorrect thermostat settings:<\/strong> A thermostat set to \u201con\u201d instead of \u201cauto\u201d can circulate unheated air between heating cycles.<\/li>\n\n\n\n<li><strong>Dirty air filter:<\/strong> Restricted airflow can cause the furnace to overheat and shut down the heating process.<\/li>\n\n\n\n<li><strong>Broken heating elements:<\/strong> Electric furnaces may blow cold air when one or more heating elements fail.<\/li>\n\n\n\n<li><strong>Damaged ductwork:<\/strong> Leaking ducts can lose heated air and allow colder air into the ventilation system.<\/li>\n<\/ul>\n\n\n\n<p>If basic thermostat and filter checks do not solve the problem, professional heating repair can identify and correct the underlying issue.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Thermostat Trouble<\/h2>\n\n\n\n<p>Sometimes a problem with a furnace isn&#8217;t a problem with a furnace at all. What we mean, is that the problem might be coming from the thermostat. Yes, it could be malfunctioning and reading indoor temperatures incorrectly or not properly regulating the temperatures, but another possibility is that user error we mentioned above. <\/p>\n\n\n\n<p>There\u2019s no reason to be embarrassed (you don\u2019t even have to\nadmit to us that this is what happened) but what we\u2019ve found in a few cases is\nthat homeowners have their thermostat set to \u201con\u201d instead of \u201cauto,\u201d and when\nthey feel cold or lukewarm air, it\u2019s because the fan is on, but the furnace isn\u2019t\ngenerating heat because the indoor temperature is <em>already <\/em>what you have set on the thermostat. <\/p>\n\n\n\n<p>Check to see if this is the case. If it\u2019s not, read on! <\/p>\n\n\n\n<h2 class=\"wp-block-heading\">A Dirty\/Clogged Air Filter<\/h2>\n\n\n\n<p>When the furnace air filter gets too clogged up, it can\nstart causing problems. What happens is that it restricts airflow <em>into <\/em>the furnace, which causes the\nsystem to overheat. When this occurs, the system will shut down as a safety\nmeasure. The fan, however, will keep blowing air to cool down the heat\nexchanger, so as a result you might feel cool air coming through the vents. <\/p>\n\n\n\n<p>You can prevent this from happening by changing your air filter out every 1\u20133 months, depending on the type of filter. Please don\u2019t hesitate to ask our professionals for guidance if you\u2019re unsure how often you should be changing yours. <\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Broken Heating Elements<\/h2>\n\n\n\n<p>So let\u2019s say the neither the thermostat or the air filter are to blame. If you have a gas-powered furnace, this doesn\u2019t apply to you, as combustion gas heats up these types of systems. But an electric furnace can suffer from broken heating elements. Our professionals can closely inspect each element to pinpoint the exact source of the problem and repair it accordingly. You want any broken heating elements repaired right away to restore functionality.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Damaged Ductwork<\/h2>\n\n\n\n<p>When there\u2019s a breach in your air ducts, warmed air can leak\nfrom the ventilation system. In addition, a breach will cause air from other\nparts of the home, most of it colder than the air from the furnace, to enter\nyour furnace. This will cause a drop in temperature. Fortunately, our team is\nhere to help. <\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Frequently Asked Questions<\/h2>\n\n\n\n<p><strong>Question: Why is my furnace blowing cold air?<\/strong><strong><br><\/strong><strong>Answer:<\/strong> A furnace may blow cold air because of an incorrect thermostat setting, a clogged air filter, broken heating elements, or damaged ductwork. Checking the thermostat and filter first can help rule out simple causes before professional furnace repair is needed.<\/p>\n\n\n\n<p><strong>Question: Should my thermostat be set to ON or AUTO for heat?<\/strong><strong><br><\/strong><strong>Answer:<\/strong> The thermostat fan should usually be set to AUTO so the blower runs only when the furnace is actively producing heat. When it is set to ON, the fan can continue circulating cool or lukewarm air between heating cycles.<\/p>\n\n\n\n<p><strong>Question: Can a dirty air filter cause my furnace to blow cold air?<\/strong><strong><br><\/strong><strong>Answer:<\/strong> Yes, a clogged air filter can restrict airflow and cause the furnace to overheat and shut down as a safety measure. The blower may continue running to cool the heat exchanger, resulting in cool air coming through your vents.<\/p>\n\n\n\n<p><strong>Question: How often should I change my furnace air filter?<\/strong><strong><br><\/strong><strong>Answer:<\/strong> Furnace air filters generally should be changed every one to three months, depending on the type of filter and your system\u2019s needs. Regular filter replacement helps maintain proper airflow and can reduce the risk of overheating and other heating problems.<\/p>\n\n\n\n<p><strong>Question: Can damaged ductwork make the air from my furnace feel cold?<\/strong><strong><br><\/strong><strong>Answer:<\/strong> Yes, damaged or leaking ductwork can allow heated air to escape before it reaches the rooms in your home. Gaps in the ducts can also draw in colder surrounding air, lowering the temperature of the air coming from your vents.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><strong>For expert <a rel=\"noreferrer noopener\" aria-label=\"heating services in Chambersburg, PA (opens in a new tab)\" href=\"\/heating\" target=\"_blank\">heating services in Chambersburg, PA<\/a> and the surrounding communities, <a href=\"\/contact\/send-a-message\" target=\"_blank\" rel=\"noreferrer noopener\" aria-label=\"contact Premier HVAC Services (opens in a new tab)\">contact Premier HVAC Services<\/a> today! <\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"<p>This is of course a frustrating problem to have. The good news is, it&#8217;s not hopeless! Here&#8217;s what might be going on. <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[76],"tags":[89,129],"class_list":["post-689","post","type-post","status-publish","format-standard","hentry","category-heating-service","tag-hagerstown","tag-heating-services"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/posts\/689","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/comments?post=689"}],"version-history":[{"count":8,"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/posts\/689\/revisions"}],"predecessor-version":[{"id":1910,"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/posts\/689\/revisions\/1910"}],"wp:attachment":[{"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/media?parent=689"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/categories?post=689"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.premierhvacpa.com\/blog\/wp-json\/wp\/v2\/tags?post=689"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}