Strange behavior

[jdf915]

I am looking at this for a friend, so me being the mechanic I can't get it to do what it is doing for me. Its symptoms are it will run fine drive fine you pull into a store get out come back go to start it and all you get is a dim air bag light then here recently it quit twice in the road now it does fine. What this? Also the vehicle is a 2003 Ford Expedition eddy Bauer edition.

 

[GAINMOB]

possible alt going bad...

 

[jdf915]

Alternator was replaced already.

 

[Bowesmobile]

I would check all electrical connections and grounds to make sure they are clean and connected firmly. Including the ones at the alternator. Pull codes and see if the PCM has anything stored.

 

[jdf915]

No codes, I was going to do the grounds already. I'll post back with results.

 

[stamp11127]

Load test the battery and voltage drop test on the positive post of the battery to alt connection and negative post to engine block.

A fully charged battery should read above 10 volts after a 15 sec load at 1/2 CCA, the VD test is limited to .5v total on both sides of the circuit.

 

[jdf915]

Load test is at 12.7 volts. Going to test grounds on Sunday.

 

[stamp11127]

Voltage seems high. How did you do the load test?

 

[jdf915]

With a volt tester while the motor was running.

 

[jdf915]

Volt tester has load test switch.

 

[stamp11127]

With the engine running tests the alternator output. A quick way is to disable the fuel pump and crank the engine for 15 seconds without interruption, watching the resulting battery voltage at the 15 second mark. This will put a load of 100-250 amps on the battery. Depending on ambient temp, above 40 degrees is 9.6v. I just call it at 10 volts above 40.

 

[Red92lx]

Check the fuse box (lower pass side), evidentially many have had to be replaced on these year expeditions.

 

[jdf915]

Check the fuse box (lower pass side), evidentially many have had to be replaced on these year expeditions.

I'll do that.