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Thread: Improving electrical wiring weaknesses in the SVO

  1. #1
    Building Boost venomizd93's Avatar
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    Improving electrical wiring weaknesses in the SVO

    So the other day while reading some recent posts I came accross the Fuel pump resistance bypass article the Mike wrote up. This got me thinking that while I have my whole car stripped out for a resto and access to all the harnesses what are ALL the wiring weaknesses in the SVO that should be upgraded so that I(we) are not going to run into issues(fires,etc.) in the future. I wrote the legend himself and he suggested a TECH tread on this when he sent his answer back. I was thinking once we got a solid list we could make it a sticky in the Electrical section. Mikes thoughts on upgrades were as follows:

    - The fuel pump circuit http://www.svocop.com/forum/showthre...ce-Wire-Bypass
    - All EEC grounds and the engine-to-chassis grounds
    - The ground wiring section for both sides of the front lights, which includes the fog circuit
    - Cooling fan power and ground circuits
    - Charging system (alternator)

    I posted the linkfor the fuel pump, but if anyone knows of other threads that have pics, diagrams, etc. that cover the other areas please feel free to add. If this does bocome a sticky maybe an administrator can modify as necessary. Just my thoughts and thanks for yoru help Mike!

  2. #2
    Some Boost JTurbo's Avatar
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    Headlight / Fog light relays....
    1979 Pace Car ~ 1982 GT T-Top
    1986 1C SVO ~ 1986 GT vert

  3. #3
    Half Boost Raven855's Avatar
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    This list could be quite extensive, what do you want to see? Simply listing the common stuff that people have done, changed, improved or had issues with :
    Alternator---3G conversion, 6G conversion, replacement
    Voltage regulator ground
    Head Light Relay
    Head light switch
    PIP
    TFI remote mount
    Fuel pump wiring
    SS Fan controller---fix, manual conversion, standard relay conversion
    Fan relay
    Fan Control Switch
    Coolant temperature sensor
    Upgrading the EEC wiring supply and ground
    IVR
    O2 sensor---ground return, 1,3, 4 wire conversion, WB conversion
    Ignition switch
    Window motors
    LED upgrades or additions
    bulbs
    Fog lights
    Ground under the battery
    Coil Ground
    Additional engine grounds
    Injector power
    wiring connectors

    This list does not cover repairing the zenier diodes in the EEC, EEC upgrades, ground loops, ground noise, ground upgrades, wire sizing, supply wire upgrades, or electrolysis.

  4. #4
    Red Captain MikeFleming's Avatar
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    Most relay installations (modifications) only deal with the power supply side of the circuit. The power return side needs some attention also, especially for the front lights and more so with higher power bulbs.

    Each side of lights (for example the right side headlight high/low, fog lamp, right inner and outer corner marker) all have ONE ground wire. Same for the left side (all those have their own ground wire). On my 84, each of those lamps had it's own ~16 gauge ground wire that were all crimped (no solder!) into ONE 16ga ground wire then screwed to the radiator core support.

    < The voices are calling me away - will add pics later >
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  5. #5
    Moderator Bob Holmes's Avatar
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    I'm not sure we have enough bandwidth to deal with this subject.
    Enough of that, it was giving me a headache.

  6. #6
    Red Captain MikeFleming's Avatar
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    I'm not sure we have enough bandwidth to deal with this subject.
    I was hoping to break it down into several "sections":

    - Repairs that don't need improvements, things where the insulation has fallen off or crumbled and can be replaced with a new wire, not needing a larger capacity wire. A poor quality wa=ire was ued but the design is correct.

    - Things that need to be improved: Need larger capacity cable, for example. This would include the design flaws such as the cooling fan controller and associated wiring; alternator feed cables and connectors, etc.

    - Things that need to be modified to handle other mods: Like adding a higher-capacity fuel pump that uses more electrical power than the stock wiring can handle; or higher wattage head/fog lamps.

    Once we get it all compiled, there won't be that many things to cover. The biggest will be the poor quality, although properly-sized, stock wiring on the 84 models. IMHO.
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  7. #7
    Building Boost venomizd93's Avatar
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    Don't know much about the differences between the 84, 85, & 86 electrical design. Did they realize the short comings in the wiring and overall design or did it carry through the model years?

  8. #8
    Red Captain MikeFleming's Avatar
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    ^
    For the most part, the design remained the same while the quality of the components used improved dramatically. In some cases no progress was made (like the alternator and charging harness and connectors) and in others it improved a bunch (the 84 has the rear window defogger wire leaving the back side of the dash, going out the RF firewall into the engine compartment, to the radiator core support, across from right to left, back to the left side of the firewall then through the A-pillar hollow areas, to the floor and on to the rear of the chassis on the left side.

    For 86 it leaves the dash switch and goes immediately left to the left side a-pillar then rearwards. Saving at least 15 feet of 12ga cable.
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  9. #9
    Half Boost Raven855's Avatar
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    They went forward with the coolant fan switch in the intake manifold. The 84-early 85 was a single wire with grounding through the engine. The 85.5-86 was 2 wires with grounding by wire to the computer. They went backwards on the O2 sensor. It was 3 wire in 84-early 85 and they dropped the heater function of the sensor and went to a single wire in 85.5-86.

  10. #10
    Red Captain MikeFleming's Avatar
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    ^
    Just a few corrections.

    The coolant temp fan switch does not go to the EEC computer, it connects to the fan controller - same as in the early cars. And Yes, feeding a single and return wire is more better electrically, with a cost and weight penalty.

    The reason to not use the more expensive heated O2 sensor was the newer, two-wire (one wire through the case) woke up faster and the EEC electronics control of fuel trim values (in the PE) was vastly improved over the earlier EEC. The 83.5/84 EFI turbo was one of the first to be managed by the EEC-IV, so the EEC development was very primitive, relatively, in those early years.

    But, alas IMHO, Ford is more run by bean counters and not so much by engineers. Still.
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  11. #11
    Half Boost rodster's Avatar
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    Quote Originally Posted by Raven855 View Post
    This list could be quite extensive, .....................
    I'm going to torch my car..... I don't want to add to the 'To Do' list.


    Great idea though to have a list for reference.

  12. #12
    Some Boost Under Pressure's Avatar
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    Mike when you replaced the connections for the alternator wires I know you used a 4 gauge for the battery did you use 10 for the other wires, F, S,A? So why did Ford keep changing the color of wire when it leaves a connector?
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  13. #13
    Some Boost SchoolBoy's Avatar
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    For me if I was start over with another svo that wasn't a 80k mile or less survivor.... I'd do these things: the 3g swap first; put the cooling fan on a relay to remove the load off the stock controller; then the relays for the lights; and on down the list from there.... This doesn't take into account any bad/burnt/butchered wiring that would need to be addressed 1st.

  14. #14
    Some Boost Under Pressure's Avatar
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    I did a lot of wire replacement and repair. I used 4 ga. for the battery to G3 150 amp Tuff Stuff and 16 ga. for the Field wire. I also eliminated a connector & a few wires. No load 13.87 volts, A/C on blower high, lights on bright, turn signal on, radio on at idle 14.22 volts no strain on this alternator. A/C works great. Good stuff.
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  15. #15
    Red Captain MikeFleming's Avatar
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    Quote Originally Posted by Under Pressure View Post
    Mike when you replaced the connections for the alternator wires I know you used a 4 gauge for the battery did you use 10 for the other wires, F, S,A? So why did Ford keep changing the color of wire when it leaves a connector?
    Some notes:

    - The alternator wire to batt + (battery level signal to the internal voltage regulator) never pulls more than 2 Amps total. All of the actual field current comes from the regulator directly to the rotor brushes - the sensor wire is just a reference line to allow the internal regulator to know battery voltage. So that wire can be 18ga and work just fine. 16ga is fine too,. anything larger is just adding weight.

    - Remember that the alternator ground comes via the bracket mounting, to the head, to the block, to the heavy ground cable that mounts near the lower power steering bracket (block), and goes onto the battery neg post. So be sure the alternator bracket to the head does not have any paint blocking the electrical path (not a good idea to just have the fastener threads carry all the current), and that the alternator body where it mounts on the large pivot bolt does not nave any anodizing or paint between those surfaces.

    - Regarding adding a 150/200A fuse in the 4ga power cable to the starter solenoid / batt terminal. Recall that the battery voltage sensing line (formerly the field wire) goes to the starter solenoid/battery + side. If the fuse blows, the alternator will still generate power as the battery voltage decreases. It's a good idea to keep the sensor wire on the alternator side of the fuse so if the fuse blows, the alternator does not over-voltage itself.
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  16. #16
    Building Boost
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    Quote Originally Posted by Bob Holmes View Post
    I'm not sure we have enough bandwidth to deal with this subject.
    HA! Love that reply...

  17. #17
    Building Boost
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    Been there... Done that...

    Over the years, I've patched, repolaced, and upgraded much of my cars wiring and pigtails.
    Add to that, the mistake of having my car soda-blasted, without removing the dash, and engine, and wiring (They masked it off, but that stuff gets in everything!)
    I've taken almost every connector apart, cleaned it, blown out baking soda, and put them back together.
    To this day (car saw soda blasted and painted 16 years ago) Whenver I drive hard in an autocross, or open track event, I still end up with little piles of baking soda on the carpet, or in my eyes. I have to wear a helmet of sunglasses at all times.

  18. #18
    Red Captain MikeFleming's Avatar
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    Pretty much need to vinegar dip the whole car after soda blasting to disolve/remove the soda residue.

    A local SVO owner here had his 65 'stang walnut shell blasted before paint. No recovery from that. Same issues you have except it's shell husks everywhere. Forever.
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  19. #19
    Some Boost Under Pressure's Avatar
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    I put a 75 amp fuse inline and cleaned all grounds. I checked the amp draw with everything turned on A/C on high 2 amps was the highest I saw. Dive real good and cool.
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