MY REVERSE LIGHT WILL NOT COME ON WHEN I PUT MY 1997 SATURN SL1 IN REVERSE

08 mercury mariner ? reverse lamps ?
Reverse lamps relay could be the problem . located in the under hood fuse / relay box. Fuse box diagram here http://www.bbbind.com/free-tsb/ enter vehicle info. year , make , model an engine . Under system click on electrical distribution , then under subsystem click on fuse panel . Click the search button ,then the blue link. The first diagram is the under hood fuse/relay box . Upper right side , along side fuel pump relay . Try replacing the relay .

reverse is a whole different circuit. via the transmission reverse switch..
my guess is you have burned out lamps.
im looking at alldata.com now. (so can you)
and i will pick the Reverse page, its boy scout simple
battery, fuse 39, wires a switch and 2 lamps.

i bet fuse 39 is blow,
replace, it. some that look good, are in fact not (micro cracks)
or use an ohm meter (dmm set to ohm low)
0 ohms good
infinity bad.

there is a fuse box in engine bay and cab.

passenger side fuse panel... change the body fuse

on the passenger side on the side of the center console

it is not really hard but make sure the ignition switch and security system will still work if you relplace it, if it has a security light in the dash when you open the door, it is harder, if it doesn't then you can do it...
remove all bottom plastic panels, all wiring connections, disconnect the yoke on the engine side of the compartment on the bottom, there are two or 4 big screws holding the column up, loosen them from the bottom, and follow steps, make sure battery is disconnected and air bag fuse is removed...this is just a general instruction.

Check the continuity of your power cables leading from the battery to the starter as well as the lines from the ignition switch. You could have a faulty connection or a bad switch.

For 1997 Saturn SL1 1.9L MFI SOHC 4cyl the Engine Control Computer is located in seating area, driver side, behind dash, upper corner, mounted on dash support brackets.

Hope help with this (remember comment and rated this).

Look for a missing / poor ground connection on the drivers side lamps.

sounds like your alternator is not charging.I would have that checked first.Also check battery terminal bolts/ cables

if there is no heat coming from the vents i would bleed the coolant system for air, usually trapped air in the system will cause this lack of heat.