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Car Forum / UK Car Forums / Classic Cars (UK group) / July 2009Polarity Conversion '65 Jaguar 3.8s
I have a 1965 S Type [1] which is still positive earth - as the range of FM radios is limited [2] the sensible option is to change the polarity. I've had and converted +ve earth cars before but these were Minors and Heralds and the Jag has a few other bits that may cause potential problems. A couple of assumptions and queries: 1. The tacho is separate from the electrical system and relies on an AC generator so a change in polarity won't affect it. 2. The clock will continue to work (the replacement parts book from SNG Barrat makes no distinction over +/- ve earth replacements) 3. The fuel pumps are the original SUs - do they have a diode? The SNG book /does/ make a distinction but I now assume that's because the replacements are not original and have polarity sensitive solid state internals. Have I made the correct assumptions, anything else? [1] http://www.sweller.dynalias.org/images/DSCF5070sml.jpg [2] I'm looking at one of these, any views/experience: http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=13428  SignatureSimon > I have a 1965 S Type [1] which is still positive earth - as the range of > FM radios is limited [2] the sensible option is to change the polarity. > I've had and converted +ve earth cars before but these were Minors and > Heralds and the Jag has a few other bits that may cause potential > problems. > A couple of assumptions and queries: > 1. The tacho is separate from the electrical system and relies on an AC > generator so a change in polarity won't affect it. I'm not familiar with this design, but my gut feeling is there will be electronics to convert the frequency from the generator into linear DC to drive a conventional meter movement. > 2. The clock will continue to work (the replacement parts book from SNG > Barrat makes no distinction over +/- ve earth replacements) That could be the case. > 3. The fuel pumps are the original SUs - do they have a diode? The SNG > book /does/ make a distinction but I now assume that's because the > replacements are not original and have polarity sensitive solid state > internals. I'd ask Burlen Fuel systems. But it would be easy enough to reverse the diodes. Assuming removing the pumps is not too difficult. I'd have thought one of the Jaguar car clubs would have the answers. > Have I made the correct assumptions, anything else? > [1] http://www.sweller.dynalias.org/images/DSCF5070sml.jpg > [2] I'm looking at one of these, any views/experience: > http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=13428 Signature*I brake for no apparent reason. Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. > > 1. The tacho is separate from the electrical system and relies on an > > AC generator so a change in polarity won't affect it. > I'm not familiar with this design, but my gut feeling is there will be > electronics to convert the frequency from the generator into linear DC to > drive a conventional meter movement. For linear read proportional. But thinking on it, if it has extra electronics it would need a battery connection. Signature*Many hamsters only blink one eye at a time * Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. > I have a 1965 S Type [1] which is still positive earth - as the range of > FM radios is limited [2] the sensible option is to change the polarity. [quoted text clipped - 21 lines] > [2] I'm looking at one of these, any views/experience: > http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=13428 If you have a Jaguar of his era and the clock still works.... it's unique! Geoff MacK > If you have a Jaguar of his era and the clock still works.... it's > unique! If it's a standard Smiths movement - I had one on an S Series Bentley - what usually happens is the internal switch contacts get dirty/burned. Since they're operated by an escapement they are by nature pretty lightweight. A cleaner spray will often get them going again. It's ages ago - but I don't remember it being difficult to dismantle the clock. I also fitted a diode across them to reduce the 'burning' - same as later SU pumps did. But it will never regulate to being accurate. These days I'd try using a voltage regulator on the supply to it. The next generation Keinzel? clocks were a half decent clockwork movement electrically wound which were pretty good - before 'quartz' became available. Signature*Age is a very high price to pay for maturity. Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> If you have a Jaguar of his era and the clock still works.... it's >> unique! [quoted text clipped - 11 lines] > electrically wound which were pretty good - before 'quartz' became > available. My P6 has a Kienzle clock. Still keeps pretty good time as well. SignaturePete M - OMF#9 Rover P6 3500 Auto Range Rover V8 Turbo (sold) Volvo 850 T5 CD Estate Mk1 Golf GTi 1.8 (Sold) "In the beginning the Universe was created. This has made a lot of people very angry and is widely regarded as a bad move." > > The next generation Keinzel? clocks were a half decent clockwork > > movement electrically wound which were pretty good - before 'quartz' > > became available. > > > My P6 has a Kienzle clock. Still keeps pretty good time as well. Main snag with those is you can't easily fit a voltage sensing alarm - ie the type that uses the interior light coming on, etc, to trigger it. As each time the clock is wound by the motor it triggers the alarm. In theory you could reduce the current taken by the motor with a resistor and capacitor but it wasn't reliable enough. Signature*If at first you don't succeed, redefine success. Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> > The next generation Keinzel? clocks were a half decent clockwork >> > movement electrically wound which were pretty good - before 'quartz' [quoted text clipped - 7 lines] > you could reduce the current taken by the motor with a resistor and > capacitor but it wasn't reliable enough. Who in their right mind would want to fit an alarm to a P6 in the first place? > > Main snag with those is you can't easily fit a voltage sensing alarm - > > ie the type that uses the interior light coming on, etc, to trigger > > it. As each time the clock is wound by the motor it triggers the > > alarm. In theory you could reduce the current taken by the motor with > > a resistor and capacitor but it wasn't reliable enough. > Who in their right mind would want to fit an alarm to a P6 in the first > place? Mine was stolen once and the rear bumper stolen on a second occasion so yes I did fit an alarm/immobilizer Signature*Someday, we'll look back on this, laugh nervously and change the subject Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. |
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