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  1. #1

    Default Brittle instrument cluster backplate

    Hi,
    I have a 1978 Mercury Zephyr Z7 that I bought recently. The car, a very clean one with 302 & auto C4, has only 56,000 original miles (sat for the last 10 years, with only a few starts on a monthly basis). I am doing some maintenance and little upgrades to make it a daily driver.

    I noticed a couple of "burnt" 194 bulbs on the gauge cluster and proceeded to remove the cluster to do so and check and clean the printed circuit board (PCB). Well, the 194 bulbs were not burned, but the holes retaining the bulb holders are eroded and thus not making contact with the PCB. The back half of the instrument cluster (aka the cluster backplate) is so brittle it literally falls apart touching it lightly. Conversely, the front panel (i.e. mask) and lens, and gauges (the simple kind with speedometer, fuel gauge and idiot lights), and the PCB are in great shape. The part number of this cluster backplate is: D8BF-10848 1$

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    The same thing happened to my 1979 F150 years ago, and I was able to get a new reproduction cluster backplate (from Dennis Carpenter) and easily transferred over the front panel and gauges to it, reusing the PCB.

    Does anybody have a good leads where could I buy a cluster backplate that fits this simpler gauge cluster with idiot lights (maybe from a 4cyl and 6-cyl Mustang 1979-1982)? I suspect there is no way to make a good contact of the bulbs with the PCB without relying on a good shape backplate hole?

    Thanks for any tips/suggestions!

    Raul
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    Last edited by chivaceae; 04-06-2020 at 12:09 AM. Reason: Corrections

  2. #2
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    Similar thing happens to the same part on the 74-78 Mustang II. I’m not sure if it is year specific. Some have it and some don’t. I have not seen it on a 74 so it might be more 77-78 plastics.
    Fox Body/3rd Gen MCA Gold Card Judge
    84 SVO 24K miles, 85 Mclaren Capri Vert. 84 GT Turbo Vert.
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    03 Mach 1 7900 miles, 74 Mustang II, 69 Mustang, 67 Mustang, 07 GT500,
    14 Mustang CS/GT, 15 F150 FTX Tuscany, 16 F250 Crewcab, 67 Tbird 47K miles

  3. #3
    FEP Super Member gr79's Avatar
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    http://vb.foureyedpride.com/showthre...-into-fairmont
    http://vb.foureyedpride.com/showthre...airmont-Zephyr

    Have same prob in my 79 Mustang. Crummy brittle plastic. WTF were the engineers thinking?
    Caused by bulb heat cycles? Whatever. The left side row of warning bulb sockets and brite light socket are ok.

    Without a spare cluster, had to improvise. Flickering or no gauge lighting sucks.

    Solved the cluster lighting problem by fabbing a custom wire harness using five rubber wedge bulb pigtails.
    Hard wired all in parallel to the hvac light circuit. If one goes out, the others stay lit like the flex pcb is.
    Added spade connectors to long wire ends for easy disconnect when removing cluster.
    They are now independent from the flex circuit power and dim normally.
    The two wire bulb sockets are rubber and fit nice and snug into the damaged holes.
    Almost 10 years of trouble free lighting since first mod.
    First mod in 2010, i used marker light pigtails inserted into rubber grommets. Ok but needed improving.
    Found the rubber socket style for the second and final config. No grommets needed, clearances ok.
    There is limited clearance back there for taller bulb socket wires when cluster is reinstalled, but they fit.
    The wiring is a little messy, but good black duct tape secures them down to the housing just fine.
    Sockets are 1/2" dia x 7/8" long, wires about 4" long.

    Example:
    https://www.parts-express.com/wedge-...SABEgIGo_D_BwE

  4. #4

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    gr79 Thanks a lot for the information and links! Now I have a couple of options. I'll look first to the one option with the rubber wedge bulb pigtails. In my case the non-functioning bulbs due to the eroded cavities are the turn signal indicators and the high beam light (the three top ones).

    I definitively need a 79-85 Mustang instrument cluster, or if I could save some $ to get me a set of Dakota Digital VHX-1014 gauges. I have seen these installed in a sleeper 10-second 4-door 1981 Zephyr (see Hot Rod magazine January 2020), and these gauges look great and "almost stock" with all the features of a full six gauge set. The cost of the Dakota VHX-1014 set is about $750, which is comparable to a full set of AutoMeter gauges, but the wiring will be tidier compared to 6 gauges plus all the ancillary lights. The pictures below show these Dakota gauges in the above mentioned 1981 four door Zephyr - pretty much the same dashboard as in my 1978 Z7 Zephyr

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    Thanks again!

    Raul
    Last edited by chivaceae; 04-07-2020 at 12:49 AM.

  5. #5
    FEP Super Member gr79's Avatar
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    Glad to help a little. Repair options help to form a plan and with decisions. More working leeway.
    Those 3 would be harder to wire prob tap into the main harness before the cluster.
    I replaced as needed, left the good ones alone untill the mod proved itself to work.
    The only ones i had to change were the back lighting sockets..

    It did not seem to make a difference to the lighting as to where the power came from.
    Did all because figured eventually the good ones would go too.
    The cluster of course is no fun to pull and install on a regular basis.

  6. #6
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    Crummy plastic instrument cluster plastic isn't limited to Ford. The cluster on my 1989 Chevy PU is in the same condition. Cost cutting, planned vehicle replacement interval, environmental concerns, pick one.

  7. #7

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    To the OP-
    I was wondering if the baking soda and super glue trick would work on the white plastic on your cluster?
    i have used this method on guitar stuff before

    79 Zephyr, 4.6L 4v/4r70w swap, with team z front and rear suspension, 8.8 and upgraded brakes and coil overs. Running Holley Terminator X Max.

  8. #8
    FEP Super Member gr79's Avatar
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    hot melt glue? Epoxy? Butyl is too soft. Tape dries out or is not tacky enough.
    The loose bulb socket contact to the printed circuit is why i used separate wired sockets.
    Could not find any way to keep the twist in sockets tight enough to stay conductive.
    Thought about some kind of metal spring to push down on them but how would the retaining screw stay in soft plastic?
    I reasoned attempts to reform the slots would only crumble more plastic supporting the repair.
    That is when i decided to use push in lighting sockets similar to some aftermarket gauges and the old way it was done.
    A push in metal bulb holder might work but heat transfer from the socket to housing plastic would be my concern.
    Am using #2825/W5W 5w 4.0 cp wedge bulbs. Brighter and get hotter than 2cp #194.
    Removed the blue bulb masks for more clearance. They were loose anyway and heat was too much for them.
    https://www.ebay.com/itm/10pcs-T10-W...oAAOSwTEpcmek1

    Have used super glue with sand (fine grains, like table salt) on metal successfully.
    Repaired a wall sconce light. The light's support tube to wall base.

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