Per the recommendations from @Zed Head , here are two excellent upgrades you can make to improve your lighting situation: Headlight relay kit: https://www.thezstore.com/product/3861/headlight-relay-upgrade-harness-70-73-240z Parking light relay kit: https://www.thezstore.com/product/5031/parking-light-upgrade-harness-70-73-240z Take note of the fitment limitation regarding the Parking Light kit for the '73 240Z. Another improvement you can make is to switch out all of your small exterior bulbs to 3W LEDs. This would be front parking and turn signal, sidemarkers, rear tail light and brake, license. If you do so, rememebr to use LEDs that are the same color as the lens cover. If making this change for the turn signals, you will also need to swtich the OE flasher cans for the turn signals and hazard switch to aftermarket electro/mechanical units, a easy plug-and-play change. Your turn signal issues are possibly caused by the heat from high resistance in your wiring circuits: corroded bulb sockets, fouled terminals in the wiring, damage at the fuse block (check the underside), damaged wiring. Hope some of this helps.