Electrical Changing from 65 gauge cluster to 66 gauge cluster

Discussion in 'Classic Mustang Specific Tech' started by 65fastbackresto, Feb 19, 2013.


  1. 65fastbackresto

    65fastbackresto Active Member

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    Ok guys been awhile since I been on here but getting geared up to get some things done. I have a 5 gauge cluster from a 66 mustang I want to put in my 65 that has the old cluster with the sweeping speedometer.

    I have an Autometer guage set under the dash with water, oil, and amp gauge. So I think all I need to work are fuel, speedometer, and background lighting on the new 66 gauges.

    I`m sure alot of you guys have done this upgrade to their cars, I`d love to hear some good ideas on how to do this, and of course I`d like to hear anything that gone wrong while doing this, as breaking things I`m working on seems to be the best talent I`ve shown thus far.
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  2. horse sence

    horse sence Please don't call me Mom SN Certified Technician

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    the mounting tabs will have to be bent forward a little to work with the 66 cluster,
    you may have to slice a little at both sides of each tab ,the last one i did i just bent them. the cluster wireing will be different from 65 -66
    #2
  3. Mr67Stang

    Mr67Stang Active Member

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    I had a '66 for a while that had bad/spliced and diced wiring under the dash. I got my hand on a complete and great condition '65 under dash wiring harness. Guess what? They are totaly different. was not trying to switch gauge clusters but as I recall, the '65 harness would not work with the '66 guage cluster. Take a look though since you already have the cluster.
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  4. 65fastbackresto

    65fastbackresto Active Member

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    Well somethings going to give, after all, all I need is working speedometer, fuel gauge, and dashlights.
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  5. Smitten65

    Smitten65 Member

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    The dash lights will work, fuel gauge, temp, hi-beam light and spedometer also. The turn signal for 65 has two wires (left and right) into the same bulb. You will need a new bulb holder (actually, two) and need to separate the wires to run to the two bulb holders. The oil pressure gauge will need to be rewired and the switch itself replaced. The pressure switch is bigger than the 65 one and will need an extention to attach to the block. They are available from most part vendors. The ammeter, however, will be a dead gauge unless you convert (or replace) and wire it for volts.
    #5
  6. 65fastbackresto

    65fastbackresto Active Member

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    Well it`s mounted in the dash, and with the advice I had from you guys about a little trimming here and there it`s looking pretty good. I would have to say this was really easy compared to what I thought it was going to be like. Thanks guys again.
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  7. Smitten65

    Smitten65 Member

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    I don't think you said if your 5 gauge cluster was from a 65 or 66 but if from a 66, I am told you CAN make the ammeter work, even with an upgraded, more powerful alternator, if you have done that also. The 66 ammeter bis a 'shunt' style ammeter that you could wire up to detect current flow. I'm not sure if it can be done with the 65 5 gauge cluster, but all you would need to do on the 66 is put an additional wire in parallel with the existing wire that goes to the battery terminal on the solenoid. Run it from the alt to the gauge and then back out to the battery. Some current will flow through that wire when charging, the bulk of the current through the heavier gauge wire charging the battery . I have not done this yet but plan on doing so later this spring.
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  8. 65fastbackresto

    65fastbackresto Active Member

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    I think it`s a 66 I`ll check it out and see if I can make that work. Thanks.
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  9. blkfrd

    blkfrd Member

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    It can be tricky to get the sensitivity of the ammeter just right without some additional tweaking. It will probably deflect more than you wish by simply putting a parallel path in for it although this is how it is designed to work (poor Ford design to begin with). You can simply put a low ohm 5 watt resistor in series with the ammeter circuit to "calibrate" the ammeter so to speak and to limit current. A fuse in line is also recommended. It only takes a few amps to fully deflect the 66 ammeter so a 5A fuse will work and will protect the ammeter from excessive current. Buy a few different resistances such as 5, 10, 15 and 20 ohms and try each of them. The ammeter should not be set up for full deflection. Only a 1/4 deflection for the highest battery load expected will be sufficient.
    #9
  10. Smitten65

    Smitten65 Member

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    Thanks, blkfrd! That is the specific information I needed but didn't have. I was going to try to do this beofe mounting the cluster. This makes it easy now to get a working ammeter!
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