For the last few years my passenger side window would go down quickly but struggle to get back up. It finally stopped working all together. I replaced the regulator and motor. It works but still goes up slowly. I lubed the guides but it didn't help much. I don't really want to burn up another motor. Any ideas?

 

I hooked it up directly to the battery and it works fine. I must have one or more weak connections or possibly a bad switch.

 

Once you get the actual problem figured out, will you try swapping the old parts back in, and then if they're ok, try to return the new ones?

 

Does the windows struggle the same if it's operated from the driver's switch AND the passenger switch? Or does it run better from one switch and not the other. Because the passenger window is grounded at one place on the passenger B pillar. But the two switches get power from two different splices.

Always start an electrical diagnosis with the GROUND side of the system.
The ground for the passenger window is located on the passenger B pillar. It's a black wire. Remove it, clean the connection, apply a dab of dielectric grease and reassemble. Then test the window. If it runs faster, you're done. If not, check for corrosion in the passenger window switch connector.

The power feed for the passenger switch comes from the circuit breaker to splice S322 located in the driver's door on the white/pink wire. From there the white/pink wire runs to the passenger door and through another splice S340 near the passenger window switch. So you'd want to do a visual check of the splices as well as a voltage drop test while the window is operating.

The power feed to the driver's switch also goes through splice S322 and then through a second splice S346 near the driver's switch