I have an overheating problem when I turn on my A/C within 5 minutes my car is overheating. It is a 2003 Infiniti G35 with a 3.5 liter engine. I have had the water pump replaced and have also replaced the thermostat.
Sounds like your high speed fan isn’t coming on. Since your car only has one cooling fan the speed is controlled with separate relays. Your vehicle has 3 separate relays to control the fan speed. The fan must be operational itself as it does not overheat unless you are running your air conditioning. Most likely one of the three relays is no longer functioning. I double checked to make sure this relay will fit your 203 Infiniti G35. They just pop in and out similar to a fuse. They are conveniently located in the under hood power distribution module engine room.