1986 Chevy El Camino Electric Motors

Ususally in cases like this it primarily a bad ground connection or the battery cables are dirty. Especially the side post batteries. Also the fan belt loosens up as well. Chevrolet's were hard on alternator belts. Clean the battery terminals and charge teh battery have it checked to see if it's anygood, most auto parts stores can do this for no charge. If they start to speed up after doiong this and your window motors don't go so fast, spray silicone in the window channels front and rear and take off the door panels and lube the regulators with white grease. The spray type works good here.

You need to do a voltage drop test on the positive and negative cables.