Most service agreements describe your equipment as it stood when you signed. That starting point matters later. What the paper says about the system on the day it enrolled can shape what it covers after that, so read the enrollment wording as closely as the coverage list.
Find the inspection terms
Look for any language about an inspection, a checkup, or a condition report at enrollment. Find out who performs it, what it looks at, whether you need to attend, and whether the paper says what happens if the inspection finds a problem. Ask whether the inspection is a condition of starting the agreement, or only a record kept for later.
Read the pre-existing condition wording
A pre-existing condition clause usually separates problems that were present before the agreement began from problems that start afterward. Read the exact definition. Check what counts as present, what evidence the paper relies on, and whether a condition found at inspection is excluded, handled after a repair, or treated some other way. Ask the seller to walk you through a plain example, and compare that example with the words on the page.
Keep your own record of the starting point
Before you sign, write down the condition of the equipment. Photograph the nameplate, the thermostat, and any visible rust, staining, or past repair. Keep older service invoices together with the paper. If a question about the starting condition comes up later, your record shows what the system looked like when you enrolled.
Questions to ask before you sign
Ask what happens if the inspection finds a problem. Ask whether a repair made before enrollment changes how the condition is treated. Ask whether a finding can exclude the whole system or only one part. Ask what record of the starting condition the seller keeps, and how you get a copy for your own folder.
Match the paper to the equipment
Check that the system named in the paper matches the unit in your home. Model, type, and location should agree. If they do not, the paper may be describing a different system. Then compare the age of the unit with the published service life on this site, using the central air conditioner page or the appliances table, so the starting point makes sense against what you already know. The paper sets the terms. Your records and the published figures help you read them.