Lighting and amps on stock electrical system-jeep yj

[LUDELVR]

Been doing some reading and just wondering how much the factory jeep yj electrical system can handle. At present I have installed some fog lights that power on with the park lights. I will admit that I used a little bit thinner gauge wire than I should have but it seems to be doing fine.

I also have a pair of spot lights (55 watt) on the windshield hinges as well as the same pair on the top of the bumper. These only come on when needed and all 4 are wired together in parallel in a 30 amp relay with a 25 amp fuse but again, the wire is a little thin but seems to be okay. I never use them for long.

I do like the look of the light bar across the top of the windscreen and am considering putting 4-5 more spot lights up top, the same 55 watt lights, and run them also in parallel but my question is, with my current setup, can my factory alternator handle the strain? These would only be on for short periods of time.

[BerserkerCatSplat]

What amperage is your current alternator? YJs came with alts of various outputs depending on option package, I think 75A was standard and 90A came if you had A/C, something like that.

2x 55W fogs + 2x 55W spots + 5x 55W spots = 495W, which is 42A current draw at 12V. That's a hefty amount of draw, especially if you've just got the 75A alt.

The good news is that alternator upgrades for the YJ are easy and pretty cheap (ZJ alts swap in with some slight grinding on the alt bracket and apparently you re-use the YJ alt's plastic wire guard). I've got a 90A you can have for free if that's more than your current alt outputs, alternatively there are also 136A units available.

[LUDELVR]

Originally posted by BerserkerCatSplat
What amperage is your current alternator? YJs came with alts of various outputs depending on option package, I think 75A was standard and 90A came if you had A/C, something like that.

2x 55W fogs + 2x 55W spots + 5x 55W spots = 495W, which is 42A current draw at 12V. That's a hefty amount of draw, especially if you've just got the 75A alt.

The good news is that alternator upgrades for the YJ are easy and pretty cheap (ZJ alts swap in with some slight grinding on the alt bracket and apparently you re-use the YJ alt's plastic wire guard). I've got a 90A you can have for free if that's more than your current alt outputs, alternatively there are also 136A units available.

You're forgetting an extra pair of spots! So it'd be 11 x 55!!

Plus, wouldn't the stock headlights, park lights, etc also contribute to the draw on the stock electrical system? So my questions are, how long would my stock electrical system take before it feels the burden of this electrical load and secondly, if I do upgrade my alternator, what type of amperes am I looking at to safely run without worry of killing my electrical system?

If your stock 90 amp alternator will work, I'd be glad to take it off of your hands but if I need something gruntier, I might as well get that. What are you running for electrical since this one is out?

[BerserkerCatSplat]

Originally posted by LUDELVR


You're forgetting an extra pair of spots! So it'd be 11 x 55!!

Plus, wouldn't the stock headlights, park lights, etc also contribute to the draw on the stock electrical system? So my questions are, how long would my stock electrical system take before it feels the burden of this electrical load and secondly, if I do upgrade my alternator, what type of amperes am I looking at to safely run without worry of killing my electrical system?

If your stock 90 amp alternator will work, I'd be glad to take it off of your hands but if I need something gruntier, I might as well get that. What are you running for electrical since this one is out?

That's a lot of lights, man.

But yes, that's draw on top of everything used to run the vehicle. Also keep in mind that advertised alternator output is peak output - at idle your alt puts out only 50-60% of its rated amperage. If you're drawing more amps than your alternator can produce, the battery will start to drain to make up the difference - which is very hard on both the alternator and the battery.

Frankly, if you're planning to install all the lights listed I'd skip the 90A and go straight to the 136A out of a '96-'98 5.2L Grand Cherokee. With that said, the first step is still to know what you've got under the hood now. Get any part numbers from your current alt so we can check the output rating, for all we know the previous owner upgraded it already.

I've currently got a 136A in my Jeep but it'll be moved to backup duty when my fresh 150A goes in this weekend. The 90A stocker is my current backup part.