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  1. #21
    Join Date
    Feb 2010
    Location
    Essex
    Posts
    232
    Hi Alan.

    I checked the V. Regulator prior to testing both temp and fuel connections looked ok as was the earth and the 'TOP' was uppermost. Fuel gauge ok when running apart from always heading towards empty 😊😊. Think i will start by swapping the sender and see how that fairs.

    Cheers

    Barry

  2. #22
    Join Date
    Jan 2017
    Location
    Mayfield, East Sussex
    Age
    51
    Posts
    126
    Hi Alan (or anyone!)

    Can I just ask quick question on voltage stabilisers - I can t find a definitive answer online. I have a similar problem as Barry - 351 Windsor runs up towards 90 deg at idle once up to temp but once the car gets moving comes down to 60 deg and I also have a very flighty fuel gauge. I just added a clock and voltmeter to the dash making 7 Smiths gauges in all (electrical rev counter, mechanical speedo, oil pressure, water temp, Fuel, voltmeter & clock) I swear that before fitting the two extra gauges the temp gauge before just sat at 90 deg most of the time. So I read online that you need a voltage stabiliser per 3 electrical smiths gauges but it worked fine before and guess the clock is excluded as just takes a straight feed and I would have assumed the same for a voltmeter - so could I need another voltage stabiliser?

    Apologies Barry for jumping in on your thread but didnt think it was worth starting a new one.

    Andrew

  3. #23
    Join Date
    May 2004
    Location
    Cowbridge, United Kingdom
    Age
    61
    Posts
    9,894
    Andrew it depends if you have the older style gauge mechanical gauges or the later digital ones.
    If the older then yes you need a second stabilizer.
    I have a new one which I bought and didn't use because my Smiths gauges are the digital variety.
    Kev Davies
    South Wales Area Rep. UKCC Membership Secretary
    DAX Mk4, 383 Chevy Stroker, Tremec. SOLD
    Contemporary CCX 3-4028, 445ci Big Block FORD FE,TKO 600, Old School IVA'd and SOLD
    Dax De Dion LS2 and T56 IVA'd June '17 SOLD
    1965 Ford Mustang 289 Convertible FOR SALE
    In build- Hawk 289 Sebring

  4. #24
    Join Date
    Feb 2010
    Location
    Essex
    Posts
    232
    Np Andrew - post on here if you stumble upon a remedy and I will do the same

    Barry

  5. #25
    Join Date
    Mar 2006
    Location
    Oxfordshire
    Age
    68
    Posts
    1,633
    Andrew,

    The voltage stabiliser is only needed for analogue gauges that measure the resistance of a sender - so that's oil/water temperature and fuel gauges. One stabiliser can feed three gauges, so with your set-up you should be OK with the one, provided you connected the new gauges to 12v rather than the 10v output from the stabiliser. However, when you modified the wiring behind the dash to add the new clock and voltmeter, it's possible you may have disturbed a wire or connector somewhere in the process - particularly earth connections.

    I was having problems with my Smiths voltmeter recently, which was reading over two volts too low. All the instruments are earthed via a bellhousing bolt. When I connected a multimeter between the bellhousing bolt and the negative terminal of the battery it showed 2.4 volts rather than zero! The problem was the earthing strap to the engine block - after cleaning this up and smearing it with Vaseline before retightening, all was well. It's quick and easy to do, so I suggest it's worthwhile checking your engine earth connection.
    Alan

    CRC Thames Valley Regional Rep
    UK Rep for European Cobra Club (eurocobra.boards.net)
    Dax 427 DeDion - Huddart SBC 383

  6. #26
    Join Date
    Jan 2017
    Location
    Mayfield, East Sussex
    Age
    51
    Posts
    126
    Thanks for all the answers - I will tinker this weekend.

    Alan - thanks for that - TBH the wiring behind the dash was pigs breakfast and I did my best to tidy it up when adding the gauges and removing the cigar lighter sockets that were front and central! I quite possibly disturbed something. The headlamp flash, horn and hazards didnt work before and still dont so the dash has to come out again anyway! Will also take a good look at the engine earth connection.

    Andrew

  7. #27
    Join Date
    Aug 2004
    Location
    Christchurch, NZ
    Age
    58
    Posts
    2,290
    My understanding of how the old 'voltage stabilisers' work is that they are simply a resistor that goes open-circuit when it gets hot. If this is the case then running two or more gauges from the same regulator is asking for trouble since the changing resistance in one sensor will affect the reading of the other gauge and vice versa. The newer solid state types do not have this problem.
    Last edited by mylesdw; 10-05-17 at 01:37 AM.
    Cheers

    Myles D-W

  8. #28
    Join Date
    May 2004
    Location
    Finchampstead, Berkshire, UK.
    Age
    54
    Posts
    3,581
    GD Mk3 Jag based
    Supercharged LS1
    GD J1M

  9. #29
    Join Date
    Jun 2003
    Location
    Brackley, Northants, England.
    Posts
    821
    There are two types of Smiths Stabilisers that I know of used with the Smiths thermal type Fuel and Water/Oil Temperature indicators.

    The first is the early Bi-Metal stabiliser that Myles D-W referred to.
    These are simply a small coil of resistance wire wound around a Bi-Metal strip contact. 12V is fed to to one side of a normally closed contact and the other side through the little coil of resistance wire the other end of which goes to ground. 12V on the unit causes the Bi-Metal strip to heat up and bend which opens the contact switching off the supply until it cools down and the cycle repeats. (It's exactly the same principle as an electric bell which uses an electromagnet instead of a heater.) The voltage across the little coil of the resistor is effectively a square waveform which switches between 12V and zero. The Bi-metal strip and resistance of the coil has been chosen such that it gives an average output of 10V out. So for 12V in and IF it was set for 6V out it would give 12V out for 50% of the time and zero for the other 50% of the time. An increase in supply voltage would cause the coil to heat up quicker so the on off ratio changes to maintain a relatively constant average of 6V. The on off ratio in the actual unit is set to give 10V out (you work out the timing!!) Of course the actual instruments being thermally operated as well don't really notice that the average 10V is really a 12V supply being interrupted. It's a very crude item but back in the late 50s and 60s there weren't many ways of producing a stabilised 10V supply at very low cost.
    Frankly I'd be very surprised if there are any of these still about. I still have one as a curiosity marked BR1307/00 or is it B81307/00 and are easily identifiable as they have a little adjusting screw located to the side of the I (Instument) Terminal.

    Later units have no adjusting screw and are a simple all Electronic transistor assisted Zener Diode stabilisers. Note that the internals of one I have here shows it has no short circuit protection so if you short it out you will almost certainly Zap it.
    I can't see any reason why the early versions wouldn't drive three instruments and certainly the later electronic types will drive three instruments according to the documentation.

    Denis

    If you take something to bits often enough, eventually you'll have two of them......


    GD427E039

  10. #30
    Join Date
    Jun 2003
    Location
    Brackley, Northants, England.
    Posts
    821
    Ah well that was a waste of time Happy Jim got his reply in whilst I was typing...
    By the way the article Happy Jim referred to suggests replacing the internals with a 3 terminal regulator a very good idea. The Regulators suggested aren't really the best bet for Automotive use but the LM2940 is and available in a 10V output.

    http://www.ti.com/lit/ds/symlink/lm2940-n.pdf

    I use these on two of my cars

    Denis

    If you take something to bits often enough, eventually you'll have two of them......


    GD427E039

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