Although the bad guy's helicopter is referred to as a "Huey" this is not correct. The Bell UH1 Huey has a much taller main rotor shaft and a 2 bladed main rotor. The bad guy's helicopter has a 4 bladed main rotor. Appears to be a Sikorsky S70i.
When Blue Thunder was malfunctioning near the power transformers the "rotor overspeed" indicator was showing and then the "Low Rotor RPM". It is not possible to have both at the same (or nearly the same) time. Of course this MAY have been done on purpose to add to the drama of the malfunction.