Tachometer goes crazy and engine lugs when I turn on the lights

Nothing. Just try not to use the headlights unless it's dark or foggy

Is car engine running at 800 rpm or more,

the battery is dead, or its ONLY discharged,12.6v is charged.

there are many fail points

battery weak,, or alternator dead.

power feeds to fuse boxes rusty

lots. and we dont worry or guess, we use a voltmeter,

and find cause in 5min, (ask any shop to do this its childs play for ase with full car electrics under belt)

the engine running, got 13.3 to 15vdc running ?

if not the CHARGE systems are failiing

note i never said any part is bad.

if you want wild guessing, you will see that here,

but not,me

we test, and never guess. ever.

"laws of physics rule" me.

get it serviced, ever hear that?

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