1990 Ford Truck draining battery

Check charging system
Need to have BATTERY DRAIN TEST
NOTE: Amperage draw will vary from vehicle to vehicle depending on equipment package.
No production vehicle should have more than a 50 mA (0.050 amp) draw.
BATTERY DRAIN TEST
1. Ensure junction box/fuse panels are accessible without turning on interior and hood lights. Drive vehicle over 30 MPH for at least 5 minutes. Park vehicle and allow to sit with ignition off for at least 40 minutes to allow electronic modules to power down.

2. Connect a fused jumper wire between negative battery cable and negative battery post. Disconnect negative battery cable from negative battery post, without breaking the jumper wire connection to prevent modules from resetting.

NOTE: It is very important that continuity is not broken between negative battery post and negative battery cable when disconnecting battery cable or connecting ammeter. If continuity is broken, go to step 1.
3. Ensure ammeter is set to read milliamps with at least a 10 amp capability. Connect ammeter between negative battery cable and negative battery post. Remove fused jumper wire.

4. If excessive current draw is present (50 mA or more), pull fuses from battery/central junction box one at a time and note any current drop when each fuse is removed. DO NOT reinstall fuses until test is complete.

5. Check wiring diagrams for any circuits that run from battery without passing through battery/central junction box. Disconnect these circuits if current draw still exists. Repair appropriate circuits as necessary.