I am going to install 2 8" 130 watt driving lights, together they will be pulling 21.9 amps. Is this load going to be too much for my stock alternator to handle? The truck is an 08 fx4, the only addons currently pulling power is a cobra radar detector and bully dog gt tuner.

 

[QUOTE=Taylor34;4658448]I am going to install 2 8" 130 watt driving lights, together they will be pulling 21.9 amps. Is this load going to be too much for my stock alternator to handle? The truck is an 08 fx4, the only addons currently pulling power is a cobra radar detector and bully dog gt tuner.


It shouldn't be. Do you know what amperage your alternator is? I know my '04 uses a 130 A alternator and, although it seems as though I read they lowered the amperage later, I definitely can't confirm that. The lowest it can be is 110 A and could well be 130 A. That should definitely be adaquate to handle the 22 A draw from the lights. What size battery do you have? While running the lights it should only be flowing through the battery, but they used a 540 CCA battery as standard (good grief, that's what came standard in the '88 Topaz 4Cyl. that my wife had), and though I hope you have a larger battery than that, it still should be OK as long as the lights are only run when the engine is running.

 

Thanks for the help. The battery is an 850 CCA, these lights will only be used when running down the highways in the Sandhills region of Nebraska where you can drive for a couple hours and only see one other car

 

ALL 04-08 truck have 110 amp small case 6g ford alternator, the 04/05 were OVERRATED at 130 amp output. that output should be more than fine since your have no other power robbing electrical items. fwiw the stock alts only come close to rated output over 4000 rpms, and only 65-75 amps at idle.

 

The biggest upgrade to the electrical system on these trucks is to do the 'BIG 3 (or4) ' wiring upgrade (in the 'how to' section). I had a small rough idle issue with my truck for what seemed like forever..enough so that I gave up on it. Anyway, after doing the up-grade it was like a total electrical rebuild, it took care of so many small issues (including the rough idle) I couldn't believe it. I know everyone will say I'm crazy...that's ok !! All I know it runs better now that it ever did new. Looks like a lot of 'heater hoses' under the hood, but, it works !!! And, yes, the standard alternator 04+ is the 110 Amp.

The only reason I bring this up in this thread is that you are starting to add items that have to find a good path back to ground. The Alt will be fine if the entire circuit is in good shape

 

Thanks for the input guys, After all this Im not to worried anymore since the lights will only be on while at highway speeds. Im definitely gonna look into doing the Big 3 wiring upgrade

 

JMT- now you've gone and burst my bubble. I was counting on that 130A, and I thought it was at idle!
65-75A at idle? What good is that? I can remember when a GM 6 cyl used a 33A alt. as standard equip., and I'm sure that WASN'T at idle! You've come a long way baby!

(course the ign., radio and headlights didn't draw much, and that's about ALL they had)