Electrical problems 2000 Expy - Resolved

[Petesexpy]

2000 expedition with 235K miles. Some weird stuff going on. First, the ABS light comes on, but braking normal. Then, tried to hook up trailer. On the trailer lights - have rear lights and turn signals, but no brake lights (normal on the car). When braking with lights on, the lights go off.
Finally, yesterday, when idling with headlights on, the driver side headlight dims, and car stalls. Cannot start the car unless lights are off (OK with PARKING lights on). Car runs normal with lights off.

Today, I tested battery (2 month old) and alternator. Battery solid 12.6 V with engine on and off. Alternator 15.6 V and no dip even when adding load, even the headlights. Interestingly, the driver side headlight dimmed and the engine stalled after about 30 seconds. Still no drop in voltage from the alt. Except now ABS light blinks about once every 5 seconds . WTF???????

 

[stamp11127]

Have alternator tested or take the voltage reading again with a second meter. The 15.6 reading is about 1v too high.

Make sure the battery connections are clean and tight before proceeding.
To load test the battery in the car, disable the fuel pump, connect meter to battery posts. Crank the starter for 30 seconds while watching the voltage reading. Let the starter cool for a minimum of two minutes (important). Crank the engine again for 30 seconds. Voltage should stay above 10.5 during the test. Should it drop below that amount the cranking capacity is too low.

Whith the engine running you should see a charging voltage between 13.5 - 14.5 volts. One problem you have is the charging voltage.

How did you get 12.6 and 15.6 with the engine running?

Sort out the battery issues then you can move to voltage drop testing.

 

[Petesexpy]

Problems resolved. Regulator went so needed new alternator. The electrical problems were two-fold - 1) after I had radiator support installed, the shop connected the ground to a painted surface, and 2) battery posts were lose. after both issues were corrected, no more electrical problems.