I am trying to replace an old bathroom fan with a light/fan combination. There is a single light switch. The unit has a blue and two white wires. The house wiring has a black, a white and a copper wire. I know the copper wire is a ground wire. I must not have the wires connected right because the light turns on but the fan doesn't. Which wires should be hooked together? The diagram in the instructions don't have the same colors of wires. Any help would be appreciated... we've spent hours trying to get this to work.

If you have 2 whites, you should also have 2 power leads,one for the light and one for the fan. Check for a wire somewhere. With 2 leads, you can have 2 switches. In your case, connect all whites to ceiling box white and power leads to the ceiling box black.

You are missing a wire in the new unit. The blue IS for the light, but there should also be a (probably) black for the fan. Open the unit and look again.