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Voltage differences?

Discussion in 'FAST Support Forum' started by J-440, Dec 4, 2017.

  1. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    1964 - that brings back some memories. Seems like that was the year performance CD ignitions started appearing in Popular Mechanics, and was also when the direction an electron traveling in a DC circuit was proven. The CD ignition actually goes back much farther. Sadly, I'm so old I still remember when race wires were solid stranded copper or stainless steel with a cheap insulator jacket. I once drove a few miles home using lamp cord after someone stole the plug wires off my new '64 Ford in a parking lot. The resistor plug wasn't around either, until after manufacturers began having to comply with EMI standards of '61. So, interference on AM radios was a big deal with an engine running anywhere nearby with those solid core wires. The graphite resistance wires back then were also real garbage. We had transistor radios in cars - but I think I remember buying my first portable transistor radio in 1964 (a leather covered Realistic AM). Where I lived then, there were no FM stations until the late '60's - and only a few FM stations then. AM ruled the airwaves. Chrysler came out with the first transistor car radio in '55. In '58, a few high end cars began getting FM radios.
    Elvis was still the only king on the radio then.
    Today, I only listen to Digital radio stations - when not playing an oldies CD. Good wiring practices were always a necessity - especially around communications equipment.

    One more thing. In '64, my air conditioning was still always "4-60" - four windows down at 60 mph. Now, I wouldn't think of driving without it.:)
     
  2. J-440

    J-440 Member

    Joined:
    Jun 16, 2012
    Well that was a waste of $250. Ran 1 gauge wire from both posts from the alternator back to the battery and got a whopping 1 volt difference on my laptop. I even added my old 4 gauge wire from the starter post to the positive alternator post. I also added a 1 gauge ground wire from the alternator to the frame. Are ya'll sure I don't need a 180amp upgrade?
     
  3. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    If you got a 1 volt improvement, that does show you significantly lowered the Ohms - a very good thing for the system. So, it wasn't a waste. You need the battery terminal ground connected directly to the engine. The rest of the changes sound fine other than 1 gauge is .480", 1/0 is .526", and 2/0 is .564" thick. The thicker the better at reducing Ohms.

    Did you check/replace the ignition switch, and are the fuse box connections clean? Check that the ignition power you used for the ECU ignition power wire is not a resistor wire, and has no resistor built into it. What voltage do you get at the connection for the ECU ignition power wire? This reading should be the same as at the battery terminals with the engine not running. It should also be very close to the software reading. If it isn't, your ECU is defective - likely due to excessive ohms caused power interference. In this case, the ECU must be returned for repair before the software can show the correct voltage.
     
  4. J-440

    J-440 Member

    Joined:
    Jun 16, 2012
    Man AA, I thought "0" was the thickest wire? So now I'm finding out that 1 gauge and 1/0 gauge aren't the same and 2/0 is thicker? I love wrenching but this electrical is pissing me off. You ought to see the spider web of wires going to the trunk of my car, the Ring Brothers would be proud!! Meanwhile I checked under the hood of my daily driver 4 banger and it has the same thickness of wires and has more electrical doo-dads and my car, with a 1/4 of the sensors, is giving me crap.
    And yes the ignition switch is good and so are the fuses. I get 11.9 volts from the wire going to the ECU (the pink one) and the thick red one from the ECU to the battery also reads the same. The laptop also reads 11.9 with the engine off. I even took some jumper cables (negative side only) and ran it up to the motor with no change on my laptop. Guess I'll try some thicker ground wire from the battery to the motor. Any other ideas?
     
  5. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Okay, we now know the ECU is good. You're getting 11.9 volts, but what are the volts reading at the battery terminals with the engine off? If the thick, main power ECU wires at the main battery terminals read 11.9, then you either have a bad terminal or the battery is at 11.9 volts. A good 12 volt battery should consistently read 12.6 volts or better at its terminals. What battery are you using? You should be using a battery in good condition capable of at least 700 cold cranking Amps, and holding 12.6 volts only moments after a ten second crank with no start. I get very good life (years) using a PC1200 Odyssey front mounted battery (the Odyssey batteries supply 550 cold cranking Amps and more amperage at high discharge than standard lead acid - up to 1200 Amps for 5 seconds). I always use larger capacity for rear mounted batteries as they help overcome some cable resistance problems (especially age related connection problems) with their higher amperage rating - 900-1100 cold cranking Amps.

    Your 1 gauge cables are borderline, but may still work. With the engine running and the alternator putting out, voltage will increase for the ECU. Both main cables need to be sized larger - not just one. A smaller wire anywhere completing this main circuit becomes the weak link. Undersized wiring creates circuit heat you don't want. Smaller than needed cables place a big load on starter relays - shortening their lifespan and making it likely their internal components will eventually weld together - causing the starter to stay engaged after releasing the start switch, and burning up the starter and cables. Think of the wires this way, if you have two 1/2" pipes flowing a needed 40 PSI of water, 1/4" pipe or fittings added anywhere inline will reduce the needed flow at the outlet. Adding 100' of 1/2" pipe in the line, with no restrictions, will also reduce the needed flow at the outlet. So, you could need to increase the pipe size to 3/4"-1" for the required flow rate at the outlet.

    Keep the ECU main power wires at least a foot away from the other wires running parallel to them. They can cross other wires at an angle to gain clearance. You could also wrap a 16 gauge wire around the length of the ECU main power wires using a 1" twist around them to help reduce interference. Ground that wire at only one end to the chassis. Tape the other end so it won't touch anything.

    One good thing, what you learn from "the school of hard knocks" isn't easily forgotten. ;)
     
  6. J-440

    J-440 Member

    Joined:
    Jun 16, 2012
    Ok, I've got the ECU wires bundled up with some other wiring going to the battery, I can insulate those. The volts reading at the battery with the car off are 12.2 along with the ECU wire. It's a brand new Optima yellow top. We've had some really cold weather lately and it's only on a trickle charger. You mentioned insulating the main power wires going to the battery. I had to separate the FAST distributor wires from my MSD wires to the coil, they didn't get along and the ECU kept throwing alarms. Going to get back to it this Wednesday and let you know how that goes. Thanks again for all the help.
     
  7. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    A good battery that has been trickle charged should be showing at least 12.6-12.7 volts. A brand new Optima should be showing more volts. I would suspect the trickle charger is bad - and may be pulling the battery down. Cold weather won't pull a new Optima down - unless you are in the Arctic and don't keep it charged. Check your other wiring isn't draining your battery. Your Optima may be in need of de-sulfating to restore capacity. I use the BatteryMINDer chargers - that will bring batteries back unless they are damaged internally. Take the trickle charger off - it's possible it may be killing the capacity of your new battery. I've had one that did that while its built-in indicator light was still showing proper operation.

    Yes, get those ECU main power wires away from all other wiring and shield them.
     

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