Pre-existing condition waiting periods apply to hospital cover,claims for hospital admissions and other benefits such as any Excess you may have had with a previous health fund.  

If you've upgraded your level of cover, a waiting period will apply to the upgraded benefits. 

During that waiting period, if you're admitted to hospital for a treatment related to the upgrade, you may be covered at your previous level cof cover, which can include an excess if your old policy had one.