You should be able to find a shop manual at your local library -- make copies of the right sections as they are usually only available in the REFERENCE section...good luck :)
The 2000 Buick Regal cooling fan circuit relay switch can be found in the fuse box. The fuse box is located in the engine compartment.
pull it and switch it with your wiper relay or a similar same part numbered one.
I believe yours has a starter mounted solenoid and not a relay.
fuse relay wiring switch
I had a similar problem w/ a 2000 Regal. The ignition switch has a circuit that is shared with the turn signals (draw up to 9A) and also controls the ignition relay. That circuit had a bad contact in the switch. I work in electronics & I worked @ this for quite a while. Had the ignition switch changed out (about $60 for switch + labor) . You still use the same lock so no change of key is required. Changed out over 3 yrs. ago & no issues since.
It could be the ignition switch or a fuse. Maybe a relay.
The 1996 Buick Century horn relay switch is located behind the dashboard. The relay switch will be on the drivers side of the dashboard.
bad relay
Mounted inside the fuel tank.
On the top of the starter where wires connect
Depending on the year, the Regal could have a relay to control the high beams. Check the distribution box under the hood to see if there is a bad headlight relay.
The 1995 Buick windshield wiper relay switch can be found in the fuse box. The windshield wiper relay switch will be in the third column, third from the top.