Originally Posted by Throapy
sorry completely brain melted on particulars.
2004, GC, selec-trac, 6 cyl engine. battery is 1 year old, no apparent(obvious) drain on it.
I don't have the equip for a volt check, but unless there's some weird drain I don't think its the battery as I had it looked at today and mech says battery, alt, and starter are ok.
Any aftermarket ignition kill or security devices on the vehicle?
As for equipment for a voltage check, a cheap DVM can be had for under $20 bucks.
A bit more if you want the nice needle point probes that allow you to carefully probe thru wire covers.
If your mechanic is not an electrical/alternator specialist, try one.
Unfortunately, there are many causes, such as the transmission interlock, the interlock relays in the under hood relay box, etc.
You will be at the mercy of a mechanic's desire to put their kids thru college unless you buy a cheap volt/ohmmeter and a factory service manual for the wiring diagrams.
Mine turned out to be a !!@#$!@#$ ignition kill that the prior owner had half removed. On cold or extra wet days, no click, no nothing.
The noise when you turned your headlights on is interesting, but it could just be one of the relays behind the glove compartment chattering/whistling because the voltage is low. The light delay relay tends to do that if it ain't getting enough voltage.
On that 6 banger, if you have a jumper cable, try jumping the - post of the battery to ground next time this happens. The grounds are notoriously poor, but easy to fix.
However, the vehicle is also notorious for getting corrosion pretty much around the body, where the rear lights and lift gate are common areas...
A couple meter leads or similarly heavy wires to jumper across suspect areas helps, as does careful use of a jumper cable to bypass the cable from battery to starter solenoid, add an extra ground, etc.