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Thread: Wiring my MkIV

  1. #1
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    Wiring my MkIV

    With the body at the paint shop for the next 4-6 weeks, I thought I would start on the wiring. I'm using the Ron Francis harness, Russ Thompson turn signal assembly, Smith gauges (got the 7 gauge kit from Peter Bayer at Nisonger), rectangular tail lights (**********), Lucas switches and Optima 34R Red Top battery. I'm waiting on a glove box kit and dash vinyl from Alex Dailey so just installed the switches, gauges and lights in the bare dash for the wiring mock up. Pretty much followed the instructions in the RF manual for all of the gauges. Once I had that completed, I fitted the dash in the car and started connecting the various switches.

    I had purchased a Lucas ignition switch (with no ACC - I later found out Lucas does make an ignition switch with an ACC connection for $50). The RF harness had ring terminals on the switch wires but the Lucas ignition switch had spade terminals. Posted on the forum as to handle the "spare" ACC wires in the harness but got no answers. I then decided to just buy a RF ignition switch (from Summit Racing) which is probably safe to say a more reliable component than the Lucas one. Also, it had male thread stud connectors so it was very easy to attach all of the switch wires (RF switch has ACC connector). Fortunately it fit the 3/4" hole I had made in the dash for the Lucas switch.

    I had wired the relay and mini starter I bought from Mark Reynolds exactly as was illustrated in the RF manual but got nothing when I turned the key. Researched the forums and found similar posts and a member had posted a picture of the suggested wiring layout. The relay has two large posts and one small one. I had run the cable from the battery and the wires from the alternator, ignition and fuse panel to one of the large post and the cable from the mini starter to the other post. The small post held the wire from the clutch safety switch that I had modified to a push button under the dash.

    The revised layout per the forum post had the cable from the mini starter moved to the same post as the cable from the battery. They had then run a #12 wire from the large post to the small post on the starter solenoid. I changed my wiring to this layout and the starter ran but sounded like the gear was not engaging with the flywheel. I pulled the starter and saw some mark on the edge of the gear ring so thought maybe the starter gear wasn't engaging all the way. I took it to the local auto electric garage and the owner tested it and showed me that it was working properly. I explained to him how I had wired it and he told me both of the large cables should not be on the same post. He told me to move it back to how I had it and he would add a jumper wire from the large cable post on the starter solenoid to the small one (see pic). I put the starter back on the engine and tried starting it again, For a second or two, the starter didn't engage but then it caught and now works fine. I need to add coolant and gas to the tank and the engine will be ready to fire.

    I did get lucky and the wipers worked correctly on the first try of the switch. I had followed the diagram that came with the wiper kit and no problems. I temporarily connected the headlights and front and rear turn signal lights. The front and rear light connectors are WeatherPack units which makes it a little tricky to temporarily connect wires to them for testing. I took some 18-20 gauge butt connectors and pushed the metal connector out of the plastic housing. I connected one end to the various light tail pieces and was then able to push the connector over the pins inside the WeatherPack connectors. Worked pretty good and the fit was tight enough to hold them in place.

    I'm using the rectangular tail lights so I had to modify the wiring since the light only has a single, double filament bulb. I wired the tail light so one bulb filament was for the tail/park lights and the turn/brake used the other filament. Actually it was simple....just put a double tail on the wire that was connected to the taller filament (which was the less bright of the two filaments). Works perfectly with the Russ Thompson turn signal setup and the stock pedal brake light switch. Since the rear of the light is open, like many members I made a rear cover for the light. I made out of fiberglass and lined it with silver foil tape that is highly reflective. Also, I replaced the stock 1157 bulbs with some RF Bright Bulbs that are 25% brighter.

    I did have a problem with the 4-way hazard switch I installed. It kept interfering with the regular turn signals. Turns out the Lucas toggle switch I was using wasn't a DPST switch which is what's required. Researching the forum I found out that you can use a SPST simple ON-OFF switch if you install some diodes in the turn signal wires. I also discovered that Lucas doesn't make a DPST toggle switch so that option is off the table. However, I had a spare wiper switch so played with it for a few minutes and got it to work without any modifications other than you have to move the toggle twice to active the 4 way flasher (the wiper switch is a OFF-ON-ON unit).

    I was real happy that I had installed a Moroso heavy duty battery disconnect switch in the trunk. It allowed me to easily disconnect the battery when I was playing with all of the wires behind the dash. I'm not making any permanent connections since I have to pull the dash to cover it. Also, while the dash is in place. I've been mapping out the best way to route the wires. The large plug connectors on the end of the dash harness and main harness really get in the way.

    Sorry for the long post. Hopefully something here will be a help to someone. The extra wires in the battery pic are for the Battery Tender charger. I just have to plug it in to the connector tied to one of the frame tubes. Works great.

    Ron

    Wire1.jpgWire2.jpgWire3.jpgWire4.jpgWire5.jpg

  2. #2
    Senior Member Big Blocker's Avatar
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    {quote} I wired the tail light so one bulb filament was for the tail/park lights and the turn/brake used the other filament. Actually it was simple....just put a double tail on the wire that was connected to the taller filament (which was the less bright of the two filaments). Works perfectly with the Russ Thompson turn signal setup and the stock pedal brake light switch. {end quote}
    I'd be interested in more detail here . . . if the (now double) tail light circuit is on at night, what does the other wire feed from that it will have any effect on the lower element?
    You are correct in wiring the brighter element to the brake/turn signal, what separates them if the TS is active and you step on the brakes?
    Sorry for the questions but separating the brake from the TS with just one element to work with is a little more complicated then adding a wire to the completely separated tail light circuit.
    I'm really, really curious and would like more details if possible.

    Doc

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    Doc,
    Thanks for the feedback on my post. Although I didn't specifically state it, you are correct that the brighter filament should be for the turn/brake circuit. The rectangular light uses a single 1157 bulb that has a double filament. One is 3 cp (for the tail light) and the other 32 cp (for the turn/brake).
    After playing with the wiring for days, I guess I was just happy to get the tail, turn and brake lights to work. I can't remember whether the brake lights over ride the turn signals or the other way around but will test some more today and post the results. Even then, I will be the first to admit that electrics is not my strong point. I followed a wiring diagram in Tex Smith's "How To Do Electrical Systems" but it didn't detail the type of turn signal assembly to be used.

    Ron

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    Doc,

    Hooked up the tail light to the rear harness plug and tested the lights again. The tail light (3 cp filament) comes on when the headlight switch is in either the "park" or "headlight" position (using Lucas OFF-ON-ON toggle switch for headlights and separate ON-ON toggle switch for dimmer) so that appears to be working correctly. I took the two wires from the turn/brake wire and connected one to the brake wire in the harness plug and the other to the turn signal plug connector. With the turn signal on, the light flashes as it should (with the tail light either on or off). When I apply the brakes, the brake light comes of and the turn signal stops flashing. I guess the question is "is this correct"? I wish I had an older vehicle with a single bulb tail light so I could check.

  5. #5
    Senior Member Big Blocker's Avatar
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    Answered with complete schematics thru PM.

    Doc

  6. #6
    Senior Member DaleG's Avatar
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    Doc, I'm going with the rect. tail lights also. Please PM schematics to me, also?
    SOLD 03/2013: MK II #5004: 5.0 EFI: 8.8, 3.55, E303, TW heads, GT40 intake, 24#, 70mm MAF

    Ordered MK IV Coyote Complete Kit.

  7. #7
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    A big thanks to Doc for sending me the schematics for the modifications so my rectangular lights work properly.

    Ron

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    Round taillight schematic

    Quote Originally Posted by Big Blocker View Post
    Answered with complete schematics thru PM.

    Doc

    Hey doc I am having the same problem but i have the two round taillights, the problem is were when the brake is on or running lights the flashers don't flash over them, I have diodes in the circuit's but obviously I don have them right, if you possibly have a schematic or could lead me in the right direction I'd very much appreciate it. Thanks Jon M.

    Have a

  9. #9
    Senior Member Big Blocker's Avatar
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    OK guys, give me this weekend to find what I sent to SCFFR . . . I send out quite a few drawings for different harnesses so I need to go back and look thru my past PM's
    If you guys want to send me a PM now with your harness and HOW you want the rear lights to work, I can send the appropriate schematic(s). Diodes don't play any part of making this work, diodes are for separating the different sides from "back-feeding" and powering the other side. Brake lights will ALWAYS over-ride TS flashers, the [brake] circuit powers the bulbs continuously - hence, NO FLASH (interrupted power to bulb).

    Doc
    FFR3712K (MKII) in Lost Wages Nevada.
    5.0 w/tubular GT-40 EFI, E303 cam, Custom 4 into 4 headers, T5, 3-Link 3.73 rear. Full F5 tubular suspension. Drop Butt mod, Dash forward mod, custom foot box air vents, custom turn signal system. 13" PBR brakes, Fiero E-Brake mod, Flaming River 18:1 rack w/ F5 bump steer kit on Breeze bushings. 17" Chrome Cobra "R's" w/ 275 fronts and 315 rears. MKIV seats. FORD Royal Blue w/ Arctic White stripes.

  10. #10
    Senior Member Big Blocker's Avatar
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    UPDATE: Seems as though Photobucket is messed up again and images won't show properly. Send me a PM and I'll send directly to anyone that needs them.

    Pretty sure this is what I sent out to almost everyone with a Ron Francis harness:



    Any questions, PM me and we can start up a conversation about your individual setup.

    This will work with either two round tail lights wired together to work as one - OR - the rectangular mod with either one or two bulbs.

    Dash indicators are not shown connected in this drawing but in application, connect to the front TS "bright" element

    This circuit is NOT for those that want upper for Brake and lower for turn signals (or vise-versa).

    Doc
    Last edited by Big Blocker; 07-23-2017 at 08:43 AM.
    FFR3712K (MKII) in Lost Wages Nevada.
    5.0 w/tubular GT-40 EFI, E303 cam, Custom 4 into 4 headers, T5, 3-Link 3.73 rear. Full F5 tubular suspension. Drop Butt mod, Dash forward mod, custom foot box air vents, custom turn signal system. 13" PBR brakes, Fiero E-Brake mod, Flaming River 18:1 rack w/ F5 bump steer kit on Breeze bushings. 17" Chrome Cobra "R's" w/ 275 fronts and 315 rears. MKIV seats. FORD Royal Blue w/ Arctic White stripes.

  11. #11
    Senior Member CraigS's Avatar
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    SCFFR, I see only one change I could recommend. That wiring going down to the starter could be slipped around to the top of that 1x1 tube. W/ the possibility of some engine rocking happening it makes me nervous having it between the tube and the bell housing.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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