So I was cruising through the junkyard a few months back and I noticed that the ford crown vic's use the same alternator as the 5.4 and 6.8 motors and the police package vics came with 200amp alternators from the factory. My truck being an 03 I grabbed an alternator off of an 04 crown vic for $40 out the door and finally got around to installing it on my truck this past weekend. before with the stereo blasting, headlights and brake lights on my battery voltages would dip down to around 12.80-12.50 on my trailer brake controller. After installing my $40 alternator I'm lucky if I can get the battery volts to drop past 13.40. Also a strange side note my truck seems to run a bit better and the shifts seem slightly firmer with the new alternator.



The best part was it was almost an entirely bolt in operation, the bigger alternator has a larger lug on it so I had to enlarge the hole on the wire from the alternator. I do plan to upgrade my power feed from the alternator to the battery, but using the stock wiring it should work for now.

If you want to upgrade your alternator just look under the hood of a crown vic and look for an alternator that has an overun clutch on it like the one below, if you pull it out there should be a tag on the side that has a ford part number and says "200" on it.

 

great project.....how is your "at idle" battery voltage?

 

At idle with all of the accessories off is at 13.80-13.90 on my trailer brake controller. Looking up the specs on the alternator it kicks out 130 amps at idle and 200 amps at higher rpms.

 

thats very good. a lot of rewound alternators have such a reduced idle output that they come with overly small pulleys so that the RPMs on the alternator spin up. smaller pulley puts a lot of drag on the engine.

btw, you don't need to change the wire to your battery.....the battery charge rate is not going to be very high and the default cable is already larger than what it needs to be.

 

Cop alternators were designed to kick out decent current at idle, since cops spend a lot of time idling.

 

I have heard ambulance alternators are high output also..

The car stereo guys turned me on to them..

 

This is a copy and paste from another thread:

Hello. I've been reading a lot on this. I have a 2003 Excursion with a V10. I have a Western Wide-Out plow on it, so I decided to up the amperage on the alternator. I went with the 200a one for the 2003 Crown Vic Interceptor. I installed it, and put 0 gauge positive and negative to the battery. It doesn't put out any amperage. I think that it's because the alternator has 3 wires, and the truck has the same plug, but only 2 wires. The wire that is missing evidently goes to the pcm on the donor car. I can get the 3-wire plug no problem, but where can I get that signal from? Thanks for any info.