Sounds like an issue with the battery or alternator. You have heat but the fan doesn't want to blow unless you rev the engine up. Check the alternator.

__________________
Lenny

There are only three sports: bullfighting, motor racing and mountaineering; all the rest are merely games. --Ernest Hemingway

'10 GL550/'04 BMW 545/'99 BMW 323/'98 ML320/'87 VW GTI (race)