Dynamo conversion to positive earth Alternator/Dynamator

[CSSType]

Hi guys. I have 1965 Stype 3.8 L Jag. All original. Its dynamo is dead. So I'm wondering what people think of the alternator selling as Dynamator on e-bay (link below) which is +ve earth hence no need to convert from +ve earth to -ve earth?
Thanks in advance.

https://rover.ebay.com/rover/1/705-5347 ... 1196.m2219

[cass3958]

There are several of these on the market I converted mine from the old generator to a Dynalite version in 2018 but I converted to negative earth at the same time so I could run a more modern radio system. Details of my conversion can be found here. http://www.jagstyperegister.com/forum_n ... earth#p802

The joy of these Dynamos is more power for running extra lights or radios but they look identical to the old generator when bolted to the side of the engine using the original bracketry. They still run the PAS in the same way the original generator does.If you are thinking of changing to a Dynamo then you should really look at converting to Negative earth. It is not hard to do so and my link will show you what to do. Apart from changing a couple of wires over and not being able to use the Jaguar clock (never worked anyway) it is very easy to do with more benefits than drawbacks.
I have not had a problem with mine and it is a great discreet upgrade.

[John Quilter]

I've been running the factory C48 dynamo in my S since new. Its output seems to be quite adequate for the car including a modern radio and a radiator cooling fan. Never had a battery run down situation. It ran reliably for decades, and some 120,000 miles but as a precaution during a major engine overhaul recently while it was off I had it rebuilt with new bearings and brushes. It is however a really heavy unit, 38 pounds including the PS pump.

[Treetrimmer]

Hi John,

It seems you are requesting opinions/experiences.
My S type is still using the original Dynamo, but the car has been converted to negative earth.
I have used numerous L.E.D. replacement bulbs, so the total electrical loading has been slightly reduced, and the Dynamo copes well.
However, if (when?) the Dynamo fails, I think I would replace it with one of the "alternators disguised as a Dynamo" because of ease of fitting, plus retention of the Power Steering pump drive.
Personally, I think it is sensible to convert to Negative earth, as ( as Cass points out) it permits the use of modern after market additions. Regarding the clock, I had mine rebuilt, using a modern quartz movement. This keeps excellent time, and utilises an external battery. The only downside is it is close to impossible to adjust the clock in situ. I therefore wired two external battery cases in parallel, so I could replace one battery at a time, without ever losing the supply to the clock.
Hope this helps you to decide on your course of action.

Richard

[CSSType]

Thank you gentlemen ! I think I will just convert to negative earth and use an Alternator... Many thanks for the replies, it does help in decision making.

[cass3958]

Not sure if you have power steering but a standard alternator will not have the pickup on the back for the PAS pump which is why theses Dynalites are so good as they use all the original housings and the PAS pump fits on the back.
The Dynalites come as + ve or - ve earth but they do not have the ability like the old generator to switch between positive and negative earth so once you have made your decision to convert the only way to go back (not that you would need to ) is to buy another Dynalite with the correct polarity or convert back to the original generator.

[Glyn Ruck]

PAS Dynalite rear.

Dynalite rear.JPG (47.22 KiB) Viewed 1323 times

[John Quilter]

Richard, FYI, my car has been converted to negative earth for a number of decades when I upgraded the radio/cassette player.

[CSSType]

Hi guys: Update: I bought a positive earth alternator fitted into dynamo body and have installed it. Its exactly like Dynalite unit (Glyn's pic). Now the next step is to identify the wires and do the correct wiring - for that I need access to the ignition switch and ignition light in the dash board. There is a relay that goes between the warning light and ignition switch. Not sure if this goes between the light and the push button starter or between the light and key-on switch. Any ideas?
Also how do I remove the dashboard to gain access to these wires? Thanks for replying.

[John Quilter]

Not sure why with this major change you would choose a positive earth alternator if negative earth ones are available. Positive earth complicates using almost all modern radio/stereo equipment, a Garman, and anything electronic. These accessories are the main reason many have converted, even their original dynamos, to negative earth. Perhaps the clock is the only thing that is not compatible with negative earth but they can be upgraded to negative if wanted and it is still even functioning.