Black mould often appears as slimy or fuzzy patches with a dark green or black coloration.

This typically grows in clusters and spreads out from a source.

Dust is usually granular or powdery.

It may vary in color depending on its composition but is typically brown, tan, or gray. Dirt doesn't usually have a defined pattern, and tends to accumulate in layers or piles.

Generally, any noise you hear that's unusual should be checked. However, if you're unsure, here is a list of some common faults represented by sound alone.

• Scraping - this could be an indoor or outdoor fan that has misaligned either due to bearing wear, or movement of the bracket or rubber.

• buzzing/popping - Relays or contactors are usually a culprit for such sounds, but it's generally reflecting a partially open circuit somewhere in your control circuit. Contact a professional immediately if you notice any of this.

• Grinding - This could be indicative of a compressor malfunction, or a bearing failure.

Yes, you can! 

Though, quotes are prepared using current commercial data, which is subject to change.

The normal expiration dates range from 30 to 40 days, but the prices will usually stay around the same even after a few months.