I replaced the ignition switch in my 1995 ford ranger now the alarm won't stop

Disconnect both battery terminals, wait a minute the renect starting with positive. Check you fuse as well or a crossed wire while you moved them

95 Ford Ranger Auto Alarm Wiring Diagram.

You need to re-check your ignition wiring. Here is the wiring for the alarm.

Battery Constant 12v+ Positive Wire (+): Yellow
Battery Constant 12v+ Positive Wire Location: Ignition Switch Harness

Starter Positive Wire (+): Red/Light Blue
Starter Positive Wire Location: Ignition Switch Harness

Ignition Positive Wire (+): Light Green/Purple
Ignition Positive Wire Location: Ignition Switch Harness

Second Ignition Positive Wire (+): Black/Light Green
Second Ignition Positive Wire Location: Ignition Switch Harness

Accessory Positive Wire (+): Gray/Yellow
Accessory Positive Wire Location: Ignition Switch Harness

Parking Light Positive Wire (+): White/Black Or Brown
Parking Light Positive Wire Location: At Headlight Switch Or Low In Drivers Kick Panel

Power Door Lock Negative Wire (-): Pink/Yellow (Type B)
Power Door Lock Negative Wire Location: In Either Kick Panel

Power Door Unlock Negative Wire (-): Pink/Light Green (Type B)
Power Door Unlock Negative Wire Location: In Either Kick Panel

Door Trigger Positive Wire (+): Black/Light Blue
Door Trigger Positive Wire Location: In Drivers Kick Panel

Domelight Supervision Wire: Use Door Trigger (Requires Relay)
Domelight Supervision Wire Location: N/A

Horn Negative Wire (-): Yellow/Light Green
Horn Negative Wire Location: At Steering Column Harness

Tachometer Wire Negative Wire (-): Any Wire With A Tan Stripe Or A Yellow Stripe
Tachometer Wire Negative Wire Location: At Ignition Coil

Brake Light Positive Wire (+): Light Green
Brake Light Positive Wire Location: At Switch Above Brake Pedal

Factory Alarm Disarm Wire (-): Dark Green/Purple
Factory Alarm Disarm Wire Location: Low In Drivers Kick Panel

Factory Anti-Theft System: N/A
Factory Anti-Theft System Location: N/A