A damp floor mat after a car wash is easy to dismiss. So is a faint musty smell that fades with the windows down. Water that gets inside a car rarely announces itself as a repair, and by the time it does, the fix may be a tracing job rather than a part swap. Before you sign any service contract, it is worth knowing what the early signs look like and how a contract may treat them.

What the early signs look like

Look for carpet that stays damp under the mats for days after the car has dried out. Press a hand flat on the carpet at the front footwells and near the rear seat anchors. A cold, wet patch is a clue even if nothing is pooled.

Watch the windows. Glass that fogs on the inside and keeps fogging, even with the fan on, can point to moisture that has nowhere to go. Water marks on the headliner, staining on the door trim, or a smell that returns after a rain are all worth writing down with the date you noticed them.

If the car has a sunroof, check whether it drips into the cabin after rain or after a wash. A sunroof that leaks is often a drain problem, and drains are easy to overlook.

Where water usually gets in

Water tends to enter through a few predictable routes. Door seals and window channels can harden, split, or sit out of line after years of use. The drain holes at the base of the windshield, under the cowl panel, can fill with leaves and grit and back water up into the footwells. Sunroof drain tubes can clog or come loose. Hose connections and grommets through the firewall can also let moisture in.

Check the spare tire well and the trunk floor too. Standing water there can point to the same kind of drain or seal problem, and it is often missed because nobody lifts the trunk floor after a wet week.

Why a contract does not settle it

A leak is often caused by a seal, a drain, or a trim fitting. Each of those parts can be treated as wear, as maintenance, or as damage from an outside source, and a contract may handle each differently. Read how the form defines wear, maintenance, and water or moisture damage. A definition that sounds narrow can decide the claim before anyone looks at the car.

Also find out who decides the cause. Tracing a water leak can take more than one visit, and it can end with a finding that the leak is excluded or was already present when the contract started. Ask whether the contract requires you to keep drains clear, and whether a failure to do so can be used to deny a claim.

What to check in the driveway

Before you buy, lift each floor mat and press the carpet. Look under the cowl panel at the base of the windshield for leaves or grit. If you can, open the sunroof and check the drain tubes at the corners. Look at the door seals for cracks or flat spots. Note anything you see, and ask the seller to explain any staining or repair work you find.

None of this is a diagnosis. A damp carpet can have more than one cause, and only a shop that is willing to trace the leak can say which one it is. The point of the check is to know what you are signing with, and to put any concern in writing before the contract starts.

Questions to ask before you sign

Ask whether water or moisture damage is listed as an exclusion, and whether a leak that is already present on the start date is treated as a known condition. Ask who pays to trace a leak, and whether the diagnosis must be done at an approved shop. Ask whether the contract requires proof of drain or seal maintenance, and what proof counts. Ask how long the waiting period lasts, and whether a leak that appears inside that period is handled differently.

Ask for the full form, not only the summary. If the company posts a sample contract, read it first. You can find companies that publish a sample on this site's list of providers that post a sample contract, and the published figures for each company are in the comparison pages linked from the top of this report.

Put it in writing

If the seller or the company tells you that a leak is covered, ask for that answer in writing and point to the clause that says so. A verbal promise about a water problem is hard to enforce once the car is in the shop. Keep the signed form, the sample you read, and your notes from the driveway check together in one folder.