I've been noticing lately that when I drive with my headlights, foglights, and defrost all on at the same time, my lights sometimes have a very faint flicker. It's like they dim a little bit for a split second, then immediately return to normal. It's not really affecting anything, but it annoys the crap out of me. My theory is that when the AC compressor kicks on for the defrost, it draws current away from the lights and dims them. What do you guys think? And do you have any suggestions on fixing it?

 

The only thing that comes to mind is if you were sitting still and the a/c compressor kicked on, the lag between that and the engine catching up to the extra load would slow down the speed of the engine - therefore the alternator and make the lights flicker dimly. There is a decent amount of current draw (not a ton, but your wiring/alternator may vary) with the fog lights and headlights running (not to mention the other 20 some odd bulbs in the vehicle).

Does anyone know if the electronicly engaged clutch on the a/c compressor can short out? That would make a flicker at any speed if the short was decent enough.

Sorry if this doesn't give you a better answer, but hopefully I can steer you in the right direction.

 

help me too!!!
Sometimes ill be driving with my lights on and they just shut off. and i need to push in the botton then pull it back out to get them to turn back on.... bad switch er something?

 

Mine does it to when the ac cluch kicks on. I'm writing it off to the amp draw

 

Are you using higher wattage than stock bulbs on stock wiring? If so, that is a known cause of that phenomenon. The fix for this issue if that is the case is purchasing or building a new headlight harness to handle the increased load.

 

Sounds like a switch to me. Is it all the lights or just the headlights?

 

The lights going off, is most likely a bad switch.....


the Flicker......
Power drain and the alternator is having a hard time keeping up with it, or the wiring is having trouble carryin the amps.
One of the best headlight mods on the XJ is to rewire them to relays, two for eeach headlight, one for low beam, and the other for high beam.
This will also be easier on the switch since it doesn't have to carry large amperage and is easier on the whole harness.
Your going to use you stock wiring to trigger the relays, and run new wires to each relay, and connect the other side of the relay to a headlight.
This will allow you to get more amperage to the lights and you will be surprised at how much batter your lights will light things up.

 

It may help to check & clean the battery connections and the ground connections.
Doug

 

will the relay trick work on a zj?

 

It should work on anything. When you build a harness with relays to bypass the stock wiring, you reduce the load that the old factory harnesses have to handle, and you put more voltage to the bulbs. Win-Win.

 

The "technical" key to all of this is eliminating voltage drop at the bulb. Even when I still ran stock headlight bulbs, if you turned the vehicle off with the headlights on, you could notice them dim (you were dropping from 13.6-14 volts down to 12 ish) and as the voltage decreases, the amp requirement increases. More amps need bigger wire. This is not to say that if your lights dim when you shut off your car that your headlight harness is bad, but it is just a symptom of components that are already at capacity. If you run aftermarket "hotter" bulbs in your rig, you should definately be using a bigger harness to deal with the demands. I ran some 80 watt lowbeams on a stock harness for a while until I saw that the harness was slowly melting from the draw of the bulbs heating the wires and connectors (over about 6 months of use). I overbuilt a new harness and haven't looked back as I love the brighter headlights for it. I'm probably ranting, but that's ok.

 

^
x2

 

Yeah, I built mine out of 10 ga wire with four 40 amp relays. Minus one failed relay that was entirely my fault, it's been flawless.

 

This:

http://www.kelleyswip.com/electric.html

And this:

http://www.eautoworks.com/Putco-H4--...s-PRD7540.aspx