Where are the bolts to remove a starter 1990 oldsmobile regency 98?

If its a 98 model, its an Oldsmobile instead of a Buick.
You should be able to take the two main bolts out plus the small brace on the end of the starter (if equipped) then drop the starter down enough to take the wires off. The solenoid stays on the starter until you get it out of the car.
Which engine is it ?

Have you asked an auto parts store to test the charging system? Usually free.

if the defroster blows then you have actutator doors not opening to the other vents.

Do you mean the two bolts on the bottom that are 9/16 right next to each other

This is what I found on the 98 Regency instructions: Crankshaft Damper REMOVAL & INSTALLATION

1. Disconnect the negative battery cable.
2. Remove the belts from the crankshaft pulley.
3. Remove the crankshaft damper attaching bolt.
4. Attach a suitable puller to the damper and remove the damper from the crankshaft. NOTE: On certain models, removal of the cooling fan, fan shroud or radiator may be necessary for clearance. WARNING
   DO NOT pry on the damper assembly to remove it from the vehicle or component damage will result. Remove the damper using a puller only.
   
5. Installation is the reverse of removal. Torque the damper bolt to specification. Fig. 1: One example of a crankshaft damper puller tool
   Fig. 2: Removing the crankshaft damper bolt Fig. 3: Do not attempt to pry on the damper to remove it from the crankshaft, use a puller only Fig. 4: Removing the damper from the crankshaft Fig. 5: When installing the damper, thread the bolt by hand first to prevent cross-threading

The starter motor for your Oldsmobile is mounted at the front lower part of the engine, just behind the radiator.
Book time to replace by an experience person is 1.1 hours.
If you are looking to do this yourself, disconnect the battery negative terminal and isolate it.
Remove any covers or braces in order to access and remove the starter.
Remove the wires to the solenoid on the starter, then the bolts retaining the starter to the engine.
There may be some shims between the starter and the engine. You may need to replace these with the new starter.
Hope your repair goes well.

KL

Review this Wiring Schematic about Olds 98 ('89, '90 & '91):
1989 1
1989 2

1990 1
1990 2

1991 1
1991 2

I really hope help you with this (remember rated this help). Good luck.

You can get a free online repair manual at autozone.com. It is free to register and gives you a repair manual for your entire car.

Those window motors are kinda tricky. Mostly just hard to get at.
Disconnect the wire harness.
Than remove the 3 bolts that hold the motor and bracket.
Remove motor from bracket.

it is under the back by the fuel tank

Code #62 in the Haynes repair manual refers to the transaxle gear switch signal circuits. Hope this answers your question..