[ROVERNET - UK] P5 Changing Polarity

McArdle fmcardle at suffolk.lib.ny.us
Tue Aug 14 14:36:31 BST 2007

Hello Eric and all, 
      Changing polarity is very easy and simple with a few caveats. 
Just fliping the battery does the job great. If you have a saloon ( non
coupe) just rev the engine up to about 1800rpm or so as soon as you start
it up the first time after reversing the battery and you will see the
charge light come on stay on , get brighter then go out. The regulator has
now reversed it self. Let it keep running like this for a minute and then
the reversal is done except for the following. 
      If you have a radio that works and want to keep it you will have to
play with it. If its the factory Blaupunkt or similar period radio there
should be a polarity provision on the back, if not you wil either have to
isolate it or best bet get a good unit and save the factory one for
concours days. 
      Depending on the vintage of you fuel pump you may have to remove and
replace the little capacitors under the covers on top of the points. These
are polarity sensitive.If you still have the original pump it probably
will not have these and you shouldn't have to do anything . 
      Here's the deal if you have a Coupe. Wires to the operating
terminals of the ammeter with need to be reversed or the ammeter will read
backwards. The wiring to the tach will have to be changed also. The power
wires will need to be reversed and the current sensor that the tach uses
to sense the ignition pulses will need to be reversed, maybe! I have seen
this work both ways in the large P5 tach so just experiment. Both ways
might work or maybe just one way , it's easy . 
      Lastly DON"T change the wiring to the coil. The SW terminal should
ALWAYS have the power to it and the IGN terminal should ALWAYS have the
distributor/points wire to it. Coils only work correctly in one direction.
They don't care if its positive or negative power getting to them and
releasing but they do care VERY much where that electricity comes in and
goes out( gets grounded). 
     Hope this helps. Contact me if you have any questions. 
Pete McArdle
Classic Racing Ent
New York 

On Mon, 13 Aug 2007, Eric Russell wrote:

> Hi,  our friend who just bought that P5 already
> mentioned has a question about changing polarity.  Can
> anyone help?
> Eric
> *****************************************
> Hi Eric:
> I have another question for the Rovernet.
> My P5 is a positive-ground car.   I would like to
> convert it to negative-ground.  Is there a proper
> procedure for this?  The fuel pumps have already been
> fried by someone (prior owner) connecting the battery
> the other way around, so they need to be rebuilt with
> negative ground “Chicklets”.  The coil and ammeter
> wires are easily switched.  However,  if I remember
> correctly there is a procedure for re-polarizing the
> generator.
> Someone has installed an electronic ignition but I
> don’t see any brand name on the black box that was
> installed on the firewall.  Do they make these things
> for positive ground or maybe it does not make any
> difference?
> Thanks,
> William J. Goggin PE
> Webmaster of The Rover Car Club of Canada
> Website:  http://www.roverclub.ca/
> Webmaster of a variety of sites from:
> http://www.websrus.ca
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