3 of the 4 power windows don't work

Yes, the switch is the next thing to check.

https://www.google.com/search?q=2008+pontiac+grand+prix+rear+defogger+not+working

https://fuse-box.info/pontiac/pontiac-grand-prix-2004-2008-fuses-and-relays

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All power originates/passes through the master control switch on the drivers door panel. Start by popping the drivers switch and with key on check power going to & through the master switch especially the switch that raises/lowers the window in question. Surely you've done checked the fuses and or relays? Hope this helps.

If you have a test light or a volt meter i can help you trouble shoot this. let me know and I'll get you the info you need.

Also what switch did you replace? the driver master switch or the right rear door switch. If you only replaced one than the other may be the problem.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

if the master switch dont make window work has to be the window motor. if its the driver side window where master switch is.remove window switch shake wires will working the switch if window try moving switch is bad. if power is at the window switch and using test light to see if power going to window motor if no window motor bad if power going to the power window motor and its trying to move window and you can hear motor working the window regulator causing binding keep window glass from going up or down.

No there all the same fuse ur window motor and regulator took a ****

If all four windows are out using the master switch you have a faulty master switch. Most of the time the master switch goes out either because the driver one time or another spilled a beverage on the switches or the wiring connector to the switch caused a short and fried the switches. Test for power at the switches. if you got power to the switches and no power at the window motors when testing you have a bad switch assembly.

mechanical or electrial ? eaither one could be cause by the window comming in out of track.

You might have a bad master switch. Generally, if a window, other than the drivers door, doesnt work at all from the mnaster switch, but does from the individual door switch, its usually a bad master.

try replacing the master switch it maybe malfunctioning due to wear.or may have shorted out by getting wet or something.since it is the primary control for all windows and power door locks.

I assume the fuses have been verified to be OK. As long as they are, it seems that either the window regulators in those doors have failed, or there is a break in the wiring between the doors. The most likely problem after fuses though is that the driver's door switches themselves have failed. Power is routed through the driver's door before being distributed to the other doors. If the driver's door switch module has died, then the other switches for those windows won't work either. A replacement driver's switch pod is easy to swap and runs around $10 at a salvage yard - I'd try that after verifying that the fusing is all OK.