used car warranty date issue

woodformoretrees

Hi, I am looking for some (any) advice as Googling the question has left me more confused.
3 months ago my son purchased a used van from a dealer, which has now developed a serious fault. If a used car warranty is set for 3 months, dated, if a fault has appeared on the second to last day of the warranty, (which can be proven via a chain of messenger conversations/emails) but the fault has not been identified by diagnostics until after the warranty is over due to mechanic workload......would the fault still be covered for repair?
I can't work out whether it's the fault, or the repair that has to have happened within the dates. The dealer says the repair (Not sure if their word is be-all-and-end all and that the warranty is just some form of courtesy, or if actually there is still any point in arguing the case)
If it is that the repair ha to have taken place that seems to be somewhat in the lap of the gods with garage availability etc, and kind of easy to weasel out of covering work within the last couple of weeks of the warranty.
I would be hugely grateful for any advice on the date issue.

Car_54

Did your son buy the van for business use?

woodformoretrees

He's an apprentice, (employed) So he uses the van to drive to and from work and carry his tools, but doesn't claim for mileage or claim the vehicle against tax.