I have an air compressor a customer got at harbor freight for me they paid for the extended warranty I no longer have there # can they do an exchange by looking up serial #?

Doubtful,there gonna do everything they can to not honor the warranty

They should exchange it on an in store credit.

Never had a problem with Harbor freight honoring a warranty.

Got. To have the one they bought to exchange

I agree with Brandon. Best bet is to call and ask but my hopes would not be up.