Another approach to solving the headlight dimming problem is to install a 'Heavy Duty Headlight Wire Harness'. One such system is available from
www.suvlights.com
The harness is easy to install and does not require removing or altering the OEM system. It provides a direct connection, using heavy gauge wire, from the battery positive terminal through supplied relays to the headlights. The factory system is then used simply to energize the relays.
The installation provided a noticeable improvement. The headlights were brighter and whiter and there was no longer any dimming, even when turning the AC on. Although not included as part of the harness assembly, I also added a 4 gauge wire ~ 9" long between the battery negative terminal and the ground plate, in parallel with the factory ground wire, as this produced a small but measurable reduction in resistance between battery negative terminal and chassis ground. Since any resistance here appears in series with the headlight bulb filaments, any reduction in resistance here is worthwhile.