Dynamo Replacement UK

[EastEndJohn]

My recently acquired 1948 P3 came with the Dynamo disassembled. Can anyone advise where I could get it re built and tested or alternatively where to acquire a replacement. I am not even sure if the car is + pos or - Neg earth as it came without a battery? many thanks

[TonyG]

John, there is very little alteration required to convert from +ve to -ve earth working on your car apart from repolarising the dynamo, reconnecting the battery the other way and swapping around the coil connections. If there is an electric fuel pump it will, most likely, be polarity conscious as well. The starter motor and wipers are unaffected.
As such, it sounds as though the only polarity indication you may have is the coil terminal connections. If SW or -ve (depending on coil age) go towards the points it is -ve earth.
However, it sounds as though you are at the stage where you can make it whatever you want. I’ve converted both my P1 and P2 to -ve working as part of their restorations. I’ve also opted to replace the dynamos with Dynamators. Clearly a departure from originality but one that ensures excellent charging at all times and probably the most sensible alteration I’ve made for modern driving. It also does away with the voltage regulator, so much simpler if you are rewiring the car. A Dynamator is an alternator that looks a bit like a dynamo and costs around £150. You will need the pulley from your old dynamo.
As an observation of a number of old cars at shows, I would urge owners to replace their original looms for new ones from Autosparks. At £200-£300 it removes so many potential faults, improves headlight functionality and helps reduce the fire risk of disintegrating wires. I’ve seen any number of cars with a nightmare of old wiring and subsequent repairs etc.
Not an easy job to replace but a bit simpler if using an alternator. Autosparks will make the loom to accommodate this and electric pumps etc, as required.
The wiring diagrams are in the workshop manual. I laid out the new loom sections on the kitchen table and identified and labelled each conductor using masking tape and writing on if it was going to or from a component. Then a matter of putting the loom in the car and joining up the sections etc. As I said, not easy but within the capability of a competent diy restorer.

I hope that helps.

Tony Gilbert

[EastEndJohn]

Very Helpful thank you Tony.

[luli]

Excellent advice!

[Spyder]

Hi Tony,

Just read your article on the Dynamator conversion. A question, what alteration did you need to make to the control box/voltage regulator since this is now within the Dynamator?

Thanks
Simon

[TonyG]

Simon,

I’m afraid I cannot say for certain how to convert existing wiring to accommodate a Dynamator. When I re wired my Tourer I specified a loom from Accuspark that was modified for alternator connection. Then I used the diagrams from the RSR workshop manual to puzzle through the modification. It was almost five years ago but I don’t recall any difficulty, just a matter of taking time and having a meter to test circuits etc.

This year I will be re fitting a recently made loom into my Saloon. This was produced to original spec so I will be modifying to accommodate a Dynamator and negative earth. Would have done it already but the lockdown has prevented me using the garage where I keep this car.

In preparation I have modified the regulator box and removed the relays etc so it will become a simple two fuse connection; one switched by the ignition and the other unswitched. To simplify this I re made the solder connections on the rear of the unit, but this isn’t really necessary. Also this renders the regulator box useless for anyone wishing to return the car to dynamo working.

Exactly how the loom needs modifying I don’t know, but I guess you are at that stage. In simple terms the alternator has two connections; one to the battery connection at the starter solenoid and one to the ignition lamp on the dash. As the connections are on the rear of the Dynamator ensure they are effectively insulated as they sit close to the distributor and you don’t want any unplanned arc welding when adjusting the points etc! You maybe able to make these two connections and leave the regulator unit untouched, isolating the old dynamo connections of course. However, without studying the diagrams I couldn’t say for certain.

My apologies that I cannot be more specific since I approached the task from a different angle, I.e re wiring with modified loom. It will be good to hear how you get on though as this may be useful when I do my other car.

Tony.

[TonyG]

My apologies, my modified loom was made by Autosparks not Accuspark. Accuspark make the Dynamator unit.

Tony.

[Spyder]

Thanks Tony for the quick reply. Mine is a special so not fully compliant wiring loom.
I'll look into this.
Thanks again.
Simon