99 ford crown vic pi...lights flicker.

i have a 1999 crown victoria police car. it starts great,runs great,all electric
stuff works great. my problem is: AT A DEAD STOP MY HEADLIGHTS AND DASHLIGHTS 'FLICKER' I have clean the battery post, checked both cables, and had the battery tested (its good). now thinking it is the alternator.
is there anything else i should know or try. I welcome any help. thanks.

It might very well be the alternator. Use a multimeter to test the voltage at the battery with the car in neutral idle and again with someone on the brakes in drive idle. If the voltage is below 13V, there is likely a problem with your alternator.

In addition to checking battery terminals, check ground points, too. Electricity doesn't flow through rust.

I would have a load test done on both the battery + alternator at your local Auto Parts store.

thanks for the info. It is the 1999 ford crown vic p71 and has the heavy duty alternator on it.
so can I just put a standard duty alt on it? It does not have all the police lights,radio,etc.
on It anymore. Also does it have a square plug or D shape plug (for alternator) on this year? once again thanks for all the help.

You need the heavy duty police alternator. The wiring harness for the standard duty is different. If you did want to go with a standard duty alternator, you will have to cut the old harness off and solder in the standard service alternator harness. You can get them from a junkyard civilian CV or Grand Marquis.

Definitely get your alternator checked. Right before mine died around 120k miles it hit 16 volts and fried my battery. Thankfully, I was barely able to limp it home from work that night.

I only wanted to spend about 100 bucks on a brand new alternator. Buy a new one if you can.

You probably don't need to spend extra for a 240A (amp) alternator unless you're running a big stereo amp. I'm having good luck in my '98 P71 with a 135A unit I purchased on eBay. Just make sure it's a Ford 6G family alternator for police w/6-groove pully and matching connector plug on the back for your wiring harness. There are a bunch of these alternators brand new on eBay right now for under 100 bucks w/ free shipping. But do have it bench tested first.

Same thing is happening to me. Its not going to be your alternator. It's most likely your headlight switch. When your headlights are on the switch is shorting out, due to the increase in current, and tripping your circuit breaker. If this doesnt fix it, check you LCM (Light Control Module). Good Luck! I know exactly how annoying this can be.

It was the alternator BUT it had damaged the battery too.
Replaced both.....NO MORE PROBLEMS.