Safest power draw for relays OR how to disable your ammeter

[paulr]

Hopefully a technical whiz can shed light here. Or, you might just find this interesting.

Got around to installing headlight relays recently...I know this is just a bandage and what is really needed is a whole car harness replacement. Let's face it, I don't have the $3grand for what is needed, which in my opinion is not a faithful replacement of the original, because, let's face it, the original is somewhat underwired from the factory, and by somewhat I don't mean somewhat. For starters, the design is missing universal terminal blocks for safe accessory mounting and/or grounding, but I digress.

Uh, the headlight relay. Keep in mind, the '64 has the quaint ammeter which is fundamentally a 10 gauge wire circuit from the alternator to the positive terminal of the solenoid with a splice in the middle, that's the ammeter safely tucked in the dash. The boiler-plate headlight relay plan is to draw power from that solenoid terminal or the battery, soldering in a fuse or fusible link. I chose a 30-amp circuit breaker and connected to the solenoid. Before replacing my old-timey headlights with anything bright, I fired her up, and initially achieved success, but noted a disabled ammeter. Previously trustworthy, now dead. It's not a question of soldering; multi-meter shows continuity through all splices.

Furthermore, if I remove the red wire to the relays and restore the black wire to the ammeter, circuit's closed and it works again.

These are my questions. Why does the inline power draw, taken off the discharge side of the ammeter cause this? And would I be better off/safer to draw power from the back of the alternator instead? Does anyone here create a terminal block such applications? Is '64 an exception to the "no-brainer" headlight relay plan?

Please don't see this as poking at Ford. I love my car. Tbird gooood. Fire baaaad.

Paul

[paulr]

Well, it's a phenomenon. When relay power is drawn from the normal place on this '64, the ammeter goes dark without explanation. YMMV. I've had enough empirical experience with my wire connected to the alternator instead to feel ok--in fact, good. The ammeter rides more steady than it did before I installed the relays, possibly because the headlight power doesn't ride there anymore, and there is certainly no compromise in headlight power.

14.1 volts measured at the back of the headlight with high RPM, high-beams on, heater on high after relays installed (and ammeter showing a "charge").

Things I like:
Confidence in the car's systems while I drive
Bright lights at night
Information from my gauges
Quantifiability

Things I don't like:
Fire--in da car
Ambivalent gauge readings
Nowhere to retrofit for safety upgrades
Creepy electrical coincidences

Next stop: Complete gauge overhaul, though my original gauges work now. This is my driver, I have to know what's going on.

For those still wondering if more voltage at the headlights make a visible difference, old light on the passenger side, new on the right:
(the right side low & high are on, the passenger side high beam was dead)


I dropped the exposure to get this definition; these are plain jane halogens with an LED halo that I wired for a manually switched DRL. The LEDs are at least as bright as the halogens. The relays are located behind the washer bag and the fuses are behind the battery. I haven't decided where to mount the switch yet, as I want it to be easily reached but invisible.