Discoloration in evaporator

This was a subdivision home appx. 3 years old. York brand hvac.

Found discoloration / staining on coils of evaporator and rusting on framework of a-coil.

Has there been leakage to make the discoloration, or is this not unusual? Isn’t rusting on this age unit premature?

I haven’t seen discoloration like this before, and recommended for HVAC evaluation.


The cooling fins look like they have a pretty significant amount of dust buil up on them. I would guess that there have been previous problems with the unit freezing up which would contribute to the rusting. The staining on the cooling fins is more than likely the result of the condensation picking up rust from the rusting steel brackets as the unit thaws out. The unit can probably be serviced by a qualified HVACR technician.

Refrigerant leak at the lower part of the staining. (if this is an upflow “A Coil”)

That is oil, which leaks with the refrigerant.

Don’t concern yourself with the rust. The evaporator coil is soaking wet during operation. Poor metal will rust.

It is an upflow ‘a coil’.

I thought it might be leakage. I know if seen on the condenser, I would look for leak in the area of discoloration.

This house had been model home, and the people were coming up to the end of the 1 yr warranty period.

Hope they listened, I advised to have serviced / evaluated by hvac.