How do I test a fridge door seal, and can I replace it myself?

A door seal is a magnetic gasket in a flexible channel, and it fails in three ways: it gets dirty and stops compressing evenly, it goes hard and takes a permanent set, or it tears at a corner. Any of those lets warm humid room air into the cabinet continuously, which makes the appliance run longer, builds frost inside, and eventually stops it holding temperature at all. It is the cheapest part on the appliance and one of the most consequential.

What you'll need

• A sheet of ordinary paper, or a £5 note
• Warm soapy water, cloths and an old toothbrush
• A hairdryer, for reshaping a distorted gasket (optional)
• A replacement gasket for your exact model (optional)
• A cross-head screwdriver, for screw-retained gaskets (optional)

Step by step

1. Clean the seal thoroughly before testing it.Warm soapy water and an old toothbrush, folding the gasket back to reach inside the channel. Crumbs, spills and mould in the folds stop it compressing. Wipe the cabinet face it seals against too, and dry both. A surprising number of failing seals pass after this.
2. Run the paper test all the way round.Close the door on a sheet of paper so half is inside, then pull it out. It should grip and drag. Repeat every 100mm along all four edges, both doors. Note precisely where it slides out freely — the location tells you what kind of failure it is.
3. Read the pattern of failures.Failure along the whole hinge side suggests the door is dropping or the appliance is out of level. Failure at the bottom corners suggests a gasket that has taken a set. A single failing section suggests a tear or a hardened spot. Failure everywhere suggests an old gasket at the end of its life.
4. Check the appliance is level and the door self-closes.A spirit level across the top and front to back. Most cold appliances are designed to sit slightly tilted back so the doors close under their own weight. Adjust the front feet. Fixing a levelling problem sometimes fixes the seal entirely.
5. Try reshaping a distorted gasket before buying a new one.Warm the flattened section gently with a hairdryer on low, keeping it moving and never letting it get hot enough to soften the plastic behind it, then work the folds back out with your fingers and hold the door shut while it cools. It often recovers a gasket that has taken a set from being squashed.
6. Identify how your gasket is fixed before ordering.Peel the inner lip back and look. A push-fit gasket has a barbed tongue pressed into a channel around the door liner. A screw-retained one is trapped by the inner door panel, held by a row of screws under the lip. A bayonet or clip-in type engages moulded lugs. Photograph it.
7. Order the gasket by model and serial number, not by measurement.Both are on the rating plate inside the fridge compartment. Gaskets are model-specific and a nearly-right one will not seal. UK and EU rules require manufacturers to keep door gaskets available for a period after a model is discontinued.
8. Let the new gasket relax before fitting it.It arrives folded in a box and will be creased and stiff. Lay it out flat in a warm room for a few hours, or drop it in warm water for a couple of minutes, so it takes its proper shape.
9. Fit a push-fit gasket from the corners inwards.Ease the old one out of the channel by pulling steadily. Start the new one at all four corners first so the lengths are right, then work the tongue into the channel along each side with your thumbs. Do not stretch it — a stretched gasket shrinks back and pulls the corners open.
10. Loosen, seat and retighten a screw-retained gasket.Slacken the screws around the inner door panel without removing them, ease the old gasket out from under the panel edge, slide the new one in, then tighten the screws progressively from the middle outwards. Removing the screws entirely lets the inner panel drop and makes the job much harder.
11. Retest with paper, and check again after a day.A new gasket beds in as it warms and compresses. Test it immediately, then again after 24 hours, and reshape any stubborn section with a hairdryer as above.

Common mistakes

• Judging a seal by looking at it — A gasket that has gone hard looks completely normal and seals nothing. The paper test takes two minutes and is the only reliable check.
• Stretching a new gasket to make it fit — It will contract as it settles and pull the corners away from the cabinet, which is exactly the failure you were trying to fix.
• Using oil or petroleum jelly to soften an old seal — It degrades the rubber and attracts dirt, so the seal fails faster. Clean it with soapy water and, if it has taken a set, reshape it with gentle heat.

If it doesn't work

Questions people ask