Wild Electrical Probs - 2000 Explorer

[SteveK2]

Hi All,
My first post here -- great forum!

My son's 2000 Ford Explorer started throwing a "fit" last night that seemed to be affect most/all electrical systems. Some examples: headlights, fog lights, instrument cluster all dimmed by about 50%, heat/AC fan blower not blowing (or at really low speed), ABS light ON, transmission making thumping/whining sounds.

We plugged in a code reader into the OBD port -- no codes stored, but as soon as the reader was plugged-in all of the problems disappeared and all electricals worked as usual. Then un-plugged the reader and the problems re-occurred.

So we disconnected the battery for 2 mins. Everything seemed fine and went for a short drive around the block. Within a 1/4 mile, the problem started again...same symptoms.

Is there any likely cause for this behavior -- electrical short, computer controller failure, etc? I've searched the forum and haven't found anything similar, so any help or advice is greatly appreciated.

TIA

 

[robertoa1a]

Perhaps a bad relay or a bad ground wire.

 

[hworksinc]

Sounds like either a bad short or ground somewhere. I doubt it has anything to do with the computer etc. - more than likely the electrical fluctuations are causing issues with the computer (ABS, trans, etc.) than the other way around.

I'd start by tracing the large power wires (both positive and negative), follow the wire down to the starter, also to the alternator. Check for frays, shorts, bad connections, etc.

Also, a failing alternator "could" cause problems like that - might want to have it checked.

 

[SteveK2]

Thanks for the suggestions, guys. It was indeed a loose ground connection behind the driver-side headlight (near the battery). Tightening up the ground has solved the problem. Thanks again!