The dreaded my dishwasher sometimes leaks or doesn't clean call

[Michael Peters]

About once or twice a month I receive a maintenance request for a dishwasher that's working but not quite right.  Either its leaking occasionally, doesn't clean like it used to, or has a weird smell.  Some are legitimate but many issues we can't recreate during a diagnosis only to leave and get another maintenance request in the next few weeks.  I'm sure more then a few of you can relate.

Wanted to see if anyone has a good rule of thumb on how to deal with these?  For appliances I have a rule of thumb that if the parts and labor exceed 50% of the cost of a new unit I'll just swap it out.  If its old or updating was already on the mind it might be half that.  With these types of dishwasher complaints I could potentially send someone out 3 times for $75-100 each and find nothing.  The real issue could be anything from its truly sporadic, dishes could be overloaded, baking sheets covering the soap dispenser, or the tenants expectations are just unreasonable.

So at what point to do just replace it or tell the tenant that they'll be charged if you have another visit that finds nothing?  Any other suggestions would be greatly appreciated.