CaptBeach

About to do the Dodge Headlight Relay Mod...scored two Bosch 40A SPST relays and pig tails, I've got the wire, shrink tubing and connectors...is this schematic one I can go by?

Also going to run a 20A breaker inline before the relays...is that enough? Also...can I run it straight off the alternators HOT + post instead of the battery?

440roadrunner

That looks OK. Some relays have diodes built in, across the coils. This is to protect against spikes in the switch circuit. Use your ohmeter, reverse the leads, and see if the coils measure same each way. If so........no diodes. If you have included diodes, they are polarity sensitive.

Good source for the supply is the starter relay battery stud. I would not hook to alternator, at least unless you have done the ammeter bypass

And don't shoot yourself in the foot on old wiring.........replace the headlight socket, and upgrade the headlight grounds. These old cars had minimal grounding from battery (engine) to body. One good way is to buy about a 1 ft starter (ring to ring) no4 cable. Look at the right front head. Those same holes!!! are available on the rear of the driver side head. Hook the cable there, and to something like a "heck" of a big through bolt through the firewall, or one of the master cylinder studs. Use star lock washers.

While you are at it, test for harness voltage drop which affects battery charging voltage.

First check running battery voltage, when warm. Should be no less than 13.5 with battery "up," everything off, and engine running fast. Should be no more than 14.5. "Best" is 13.8---14.2

If you are much above this, you have drop in the positive ignition harness. To check that, put one probe of your meter on the regulator IGN terminal, key on, engine off. With the meter in low DC volts, put the other probe on the battery pos. stud. You are hoping for a very low reading the LOWER the better. More than about .3V (three tenths of a volt) means you have a volt. drop problem.

Also check the GROUND side for drop. With engine running fast, stick one probe on the battery NEG post, the other onto the regulator mounting flange. Once more, you hope for a low reading. Check again with lights, heater, etc on. Over .3V means you need to improve the battery.....block.....body ground.

If you haven't done so, read here:

http://www.madelectrical.com/electrical-tech.shtml

ammeter bypass:

Even if you don't do this, it points out the pitfalls

http://www.madelectrical.com/electri...p-gauges.shtml

and this, on headlights

http://www.madelectrical.com/electri...adlights.shtml

CaptBeach

I was already leaning towards using that stud vs running wire to the hot side of the alternator...thanks...good scoop there...THAT is why I'm here...