CVR Rebuild

Discussion in 'General IH Tech' started by George Womack, Mar 14, 2013.


  1. George Womack

    George Womack Y-Block King

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    I posted this over on JustIH.org; thought I would post here, too.



    I've made new CVR units using solid state components for my 800s, but had never replaced one in a Scout II. The Scout 800 CVR connects with regular spade terminals, so there's no need to use the OEM metal case when replacing the CVR. But the Scout II unit is different. When the gauges went haywire this week in GF Lauren's Terra, I traced to problem to a non-functional CVR. Since the Scout II CVR screws to the back of the TEMPERATURE/OIL PRESSURE gauge unit and makes contact with the back of the printed circuit board, I thought it would be cool to use the stock metal case of the CVR and replace the innards with solid state components. It's easy to do, and just requires two components--a 5VDC regulator and a 10uF capacitor. Here's a quickie overview of the job.

    [​IMG]
    Here's the stock CVR. The little tabs on the back of the "board" contact the printed circuit board on the back of the gauge unit. You will reuse the board with these tabs. Bend the metal of the case so you can remove the board. I used a small chisel and pliers. Be careful not to damage the board.


    [​IMG]
    Here's what's inside. You can see the broken wire on the heating coil. Break off everything, leaving the rivets that hold the tabs shown in the previous photo. Solder the components together and attach the 5VDC voltage regulator to the case using a small machine screw & nut. I used heat sink compound on the back of the regulator; this helps the transfer of heat from the regulator to the metal case.


    [​IMG]
    The new components installed in the metal case. Solder wires to the prongs of the regulator, and solder the other ends of the wires to the rivets on the board. Extra points for using green wire! The center prong of the regulator is the ground. I soldered a wire to this prong and then soldered the wire to the case after drilling a hole for it. Put the board back in place and bend the lips of the case back around it. Now the rebuilt CVR unit can be reinstalled just like stock.

    See my component list and schematic in post #6 of this thread: http://www.binderplanet.com/forums/showthread.php?t=92188&highlight=CVR
    Note that plan is for a Scout 800 and uses a separate heat sink; all you need in this case are the 276-1770 regulator and the 272-1025 capacitor.


    Attached Thumbnails



    keywords CVR constant voltage regulator 5V volt volts
     

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  2. tdruxpin

    tdruxpin Farmall Cub

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    Last edited: Mar 14, 2013
  3. George Womack

    George Womack Y-Block King

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    Thanks, I corrected the link.
     
  4. black670

    black670 Farmall Cub

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    Okay, I have a 76 II, 345, 4 speed, etc... Tried the BW307, followed the schematics given by Caperodder. Hook it up and noticed smoke coming from my dash... Shut the vehicle down and checked the gauge pod. I did not notice any burn marks but I think a tab from the 307 may have been touching the metal dash. bent the tab, reattached the pod and I still have nothing... Before my Temp gauge would register, fuel gauge was hit and miss, and the oil pressure was nada. Even put a new oil pressure sending unit in.

    After I did all this, now my temp gauge doesent even register... Hmm? Any help...
     
  5. westww

    westww Farmall Cub

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    Thanks for the great info. I tried it your way but apparently I am not as skilled with the soldering iron as you. By they time i got connections working there was no way it was going to fit back in the old CVR case. So, I put your schematic and hardware on the outside of the old case and used it as a heat sink. Then wired it similar to the ones at scout parts.com and in the knowledge base article. It seems to be working so far. Thanks again for the great write up[​IMG][​IMG]

    Sent from my Nexus 7 using Tapatalk
     

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