Dynostart wiring

[Andrew]

Hello Talboteers,
Enquiring if any of you experienced gearheads could offer some guidance? I'm up in Ayrshire Scotland replacing wiring on two separate Talbots, a 90 race replica chassis and a convertible 1932. I'm pretty decent at wiring but am still learning about Talbots as I go. These larger 24v dynostarts have two wire connections, the "field" smaller connection and the larger "starting" connection. I am using a Lucas basic voltage regulator instead of the original "cut out" switch - here's my question:

Does the larger starter wire also provide the charging output back to the battery? So that large connection (circuit 5) in addition to being connected to the 24v converter, would also be a circuit to the dyno output connection on the voltage regulator, while the smaller (circuit 7) is the "field" circuit which would go to the "F" on the voltage reg? This is my best impression after reading several pages of dynostart info and studying the various years wiring diagrams from the Talbot site and manual.

If so, if the dynostart is receiving 24v and there's a circuit back to the voltage regulator from the 24v connection, would that be a hazard to the voltage regulator, sending 24v up the pipe to the black box?

Thank you so much for reading, any tips you could provide would be welcome. I'm getting there, slowly!

Regards,

Andrew Horn
Stair Automotive

PS. I really enjoyed the latest issue of the magazine, with the profile of my new friend John Dodd and the double page spread of the famous race painting!

[Andrew]

We are in the middle of working this out with Ian Potts and John Dodd, and will report with a solution as soon as possible.

[Guy Gregory]

Hi Andrew. If you want I can send you the wiring instructions for the 24v solenoid the STD sells. I would need to email it to you as its too big a file for here. Best wishes Guy

[Andrew]

Hello Guy thanks for your offer. We got it sorted through an unconventional set up.

This whole project turned into a delicate house of cards which each having to be in the just correct position!

The crux of the issue is we are using a Mercedez 12-24v converter. The converter then activates a standard 24v starting solenoid (to prevent 12v from being applied the rest of the time). The Mercedes unit worked fine for converting to 24v, but unlike the original Talbot equipment, there wasn't a special grounding post on the switch that allowed the cutout / regulator to be limited to only receiving 12v back up the dynastart output. This is a feature with the Talbot where 24v cars must be grounded back to the switch instead of the chassis, limiting the flow of the 24v current.

This meant for us, when the 24v was being applied to the Dynastart, then 24v was ALSO flying up the connection to the fuse board, blowing the main fuse and also potentially burning out the aftermarket Lucas style regulator.
I was going to use the Talbot Owner's Club circuit based regulator that Ian Potts did a nice job of designing. He gave me quite a lot of assistance via email and sent over the regulator. However this was ideally to be paired with the Talbot original 24v cut out which we did not have, and are near nigh impossible to find. Instead I needed to use the widely available Lucas Style RB340 25 amp regulator.

The solution was to install a "normally closed" heavy duty 12v relay in the line from the Dynastart output to the Lucas Voltage Regulator. This is a relay that is sort of opposite from most in that it is normally always in a full connection, and disconnects the circuit, e.g. opening, when power is applied. This relay is activated by the start switch, so right as the moment the 24v converter is being activated, the circuit from the dynastart output is being disconnected. It works.

This is the relay:

https://www.arc-components.com/0-727...reak-2146.html

So then installing the RB340 Regulator in a standard configuration, the charging system functions properly.

That's the short story that took several weeks to sort out. Thanks folks for reading and all the great documentation we have from the club. Moving on!