I have a 97 ford ranger 2.3l 4cylinder 4x2. I just had the thermostat changed and fuel pump changed along with the cleaning of the mass air flow. Now it runs better but if I turn the lights on they are dim and the interior lights won't work. Also the windshield wipers won't work unless all the other things are turned off. The turn signals will not even work if the headlights or something else is on? The alternator battery and starter all check out good. Please help me figure out what it might be. If I just run one of the lights or wipers its fine or acts sluggish or dim with the lights.

 

Sounds like it might be a ground problem. Check ground points under hood. There should be one by the battery on radiator support and another by BJB on the left hand side of fender.

 

Yes, could be a ground issue.

Battery ground cable often has 2 leads, a large one for the engine(starter motor) and a smaller one going to the Radiator Support, that's the head light ground.

Should also be a ground wire/strap from engine to firewall and/or frame.
There are 4 things that need good clean grounds
Rad support
Engine block
Frame
Firewall
These 4 things are separated by rubber mounts so need to be grounded together with cables.

If you have a Voltmeter measure battery voltage, then with key on, engine off, pull some fuses out(one at a time) and measure voltage from the fuse connection to ground, bolt or bare metal on body, if voltage is less than battery voltage then run a wire from negative on battery to your meter, if voltage goes up then you have a ground issue, if voltage stays low then you have a 12v issue, full 12v power is not getting from battery to power distribution areas.