The fuel pump is in the fuel tank.
The coolant fan switch is located close to the thermostat.
the ecm on this van is on the passenger side behind the plastic kick plate
in the tank
According to the HAYNES REPAIR MANUAL the 1990 Astro Van has a 17 gallon tank.
Yes it did. I own (still) a 1990 Astro camper-conversion van with crank up windows.
1990 Chevrolet Lumina temperature sender is located on the back side of the thermostat housing. The sender has a wire that goes to the temperature gauge.
Yes. The lug pattern is the same on all Astro vans up to 2001. 2002 they went to a six lug pattern.
Drain the 90 Astros radiator into a pan. Dispose of the coolant properly as it is toxic to animals. Remove the top radiator hose and water inlet. Remove the thermostat from under the inlet and replace. reverse the procedures to finish the installation.
I own a 1990 Chevy Astro Van and the turn signal flasher is located underneath the steering wheel below the lever for the engine hood. An easy way to find it is to signal left and listen for the flasher unit clicking.