Lights blinking

[qokuh]

When I go past 70mph (on the dot) my lights (interior) start to flicker slightly. This is an alturnator issue? I think it is but i am wondering if it is the belt slipping too?! Please help. If I need a new alt. how much is it on average to get installed?

Thanks.

 

[Tony2005]

Could be belt, tensioner, wiring or alternator. Check condition of belt and tensioner. What year, engine and mileage?

 

[95SVT]

I had a similar problem once, but at low speeds. At night the headlight intensity varied with the dash lights. Turned out that the nut holding the main power cable on the alternator wasn't tight.