My friend just called me to ask if i may know what may be causing his car to overheat.

heres the scoup:

Car doesnt overheat while cruising on highway even with a/c on.
once car comes to a stop / idle it begins to go up.

he checked the fuses, relays and they are all good. We're thinking its the thermastat but not sure.

what can the potential issues be?

theres a honda dealership by his job so if its a relay or something he'll go buy it and swap it out.