DDK - Die Deutschen Klassiker

Ok, so I'm an electronics man, and don't know what this is for.
My car should have one (I think) I have wiring for one (I believe that is what the spare wires are for) Can anyone lend me one ?
Mine is a '69 T but running a 2.4 on Zeniths. I have the three terminal CDI, but to drive the Tacho, the Haynes wiring diagram (admittedly for a '69 E or S) shows next to item 10 (The CDI) and item 8 (The switching SCR) driving the black and purple wire that feeds to the tacho.
My tacho is driven directly off the +ve side of the coil. It works fine, as does the car. I am just curious to know what the missing bit is, and what it does. My guess is that it provides an ignition isolated feed to the tacho, so, in the event of a tacho fault, the tacho doesn't kill the engine.
Anyone ??

Cheers

That's interesting Tim: looking at my '73 wiring diagram (p 222 haynes) it looks as though my tacho should go through Number 11 (speed switch). If that is the same as either '3 RPM sensor' or '5 RPM Transducer' top picture p 206 then both are missing on mine, and the tacho is (I'm pretty sure, but will check) connected directly to the dizzy points connection.

BTW, are your 'spare' wires up around the engine compartment electriacal panel, or under the dash?

The spare wires thaI have are in the engine compartment, alongside the CDI box.

There is an RPM transducer, throttle micro switch, and solenoids that are used on the Zenith carbs to richen the mixture on overrun over a set RPM. This is a strange thing to want to do I think, but there it is ! This is not connected on my car.... infact I have spare wires where the RPM transducer used to be too.... (That too on the wiring panel in the engine compartment)
I don't have the Haynes book with me, so can't refer to the things you point out, Will look tonight if I get a chance.
Tim

Tim,

Thanks for your advice on CDI units under the ACE cafe topic. Thought I'd best relocate here under this thread so as not to go "off topic". First things first. I think that scr unit was deleted on the later cars. My 73 does not have one and my 70 model T does and I think that is the way it should be (nothing appears to be missing). My problem developed like this. A chap rebuilt the engine on the '73 but said the car had left him stranded because the CDI unit had blown. He replaced it and the car ran fine but now the tacho did not work. I popped the car away for the winter and got it out again a few weeks ago. I went to troubleshoot the situation and some knowledgeable person on Pelican Parts forum got hold of a wiring diagram for this system that is clearer than the haynes. I think it must be for the earlier cars as it shows what I think you refer to as the SCR as a Ballast unit. Item 2 on the diagram that I've posted here as it might help with identifying your system.





This is the system in the '70. With scr / ballast unit.



This is the system in the '73 without scr / ballast unit. I guess it feeds the tacho from the coil or the points. A little delving would prove which.

So I took a look at the car and the reason the tacho did not work was down to the black purple feed wire being disconnected at the Tacho. I wonder if he puled this when fiddling with the CD problem and forgot to re attach it. He hates electrics - told me so. Prefers building race engines. So I reattached the wire and presto 1 functioning tacho and 1 motor that pulled strong. All fine and dandy until I left you chaps at the ACE and opened it up on the A1. Thats when it started to pop and bang. Pulled over, checked the motor over, ran OK. Fine all the way up the A1 at cruising speed. Opened it up again near my house. Hit the red line a couple of times no problems. I phoned the guys at carrera performance that do a lot of early cars. They reckoned it was the CDI. They said if it is popping back through the induction and back firing that is the failure mode associated with break down of the CDI unit. It typically happens when the engine is under load creating a lot of heat, resistance increases with temperature (dry joints?) pop pop pop. You panic, pull over, and the engine bay cools. The CDI goes out of the critical temp range and all's tickity boo again - until the next time you start pressing on.

I think I have 2 possibilities, leave off the tacho wire like you suggest which if it made it better may confirm that it was not the CDI, or swap in the CDI from the T.

That would at least prove a point but I think I'm going to be stuck for a unit if it proves to be that. If the T one cures it I still need a unit when the T hits the road. There was a chap repairing them on an exchange basis but he has gone to ground. At least that proves that it can be done. Any ideas Tim?

BTW: R U going to Beaulieu on the 22nd???

impmad2000 wrote:Ok, so I'm an electronics man, and don't know what this is for.
My car should have one (I think) I have wiring for one (I believe that is what the spare wires are for) Can anyone lend me one ?
Mine is a '69 T but running a 2.4 on Zeniths. I have the three terminal CDI, but to drive the Tacho, the Haynes wiring diagram (admittedly for a '69 E or S) shows next to item 10 (The CDI) and item 8 (The switching SCR) driving the black and purple wire that feeds to the tacho.
My tacho is driven directly off the +ve side of the coil. It works fine, as does the car. I am just curious to know what the missing bit is, and what it does. My guess is that it provides an ignition isolated feed to the tacho, so, in the event of a tacho fault, the tacho doesn't kill the engine.
Anyone ??

Cheers

Tim,

Thanks for your private message this a.m. I prepped up a return e mail with a better copy of the diagram and more blurb. However I think there might be a problem with the return as although it dumped it in sent items it also generated a server return error 501. I tried again but still not convinced. Did you get it???

Thanks Keith, I do have the email. The picture is a little clearer. I think I can work from that. I am not going to Beaulieu, so perhaps you can post it. I'll pm you my address if that is a goer. Let me know.

Tim