Hi everyone my name is Matt and I own a 2003 Subaru Imprza WRX Turbo.

I have owned the car for about 8 months now and I have had this problem since i got it.

The problem occurs when I turn the lights, the heater and window wipers (and most of the other electrical equipment in the car) at which point the car begins to judder and hold back. So far I have put two different alternators on the car and a brand new battery.

Any help would be greatly appreciated.

Many Thanks

Matt.F

Hi n welcome,  first thing that springs to mind would be to check all earth's are making good contact and free from corrosion. Think There's two on the inlet manifold for the engine loom and 1 attached to the starter motor bolt . If they're still attached,  try giving them a clean to see if that helps your symptoms. 

If you can get the problem to happen when the car is sitting still ticking over there is an easy way to check the earths.

Connect a jump lead to the negative battery terminal. Connect the other end to a bare metal part of the engine. If the fault disappears then you need to do as savage bulldogs suggested. Remember to clean the area the terminals contact as well as the terminals themselves.

Might be an idea to check the other terminals at the alternator and battery. I've seen plenty alternators and batteries replaced and connected back up to manky corroded terminals.