K2543 functions for a few kms

Kits Automotive projects
1

Hello,

Three weeks ago I installed a K2543 ignition kit in a 6 V Renault Dauphine. The kit was mounted entirely inside the recommended G304 box.
The engine ran beautifully, like violins in a Mozart suite. For 90 kms. In the pouring rain, in a motorway stew, she made a few irregular strokes and then stopped suddenly. The engine would not start again. After 30 mins, I tried again and the engine marched for 30 secs. After this, I restored the original situation and my car brought me home without a problem.

I did several attempts with the kit. The last time, I made a rectangular hole in the box and mounted the cooler on the outside, but firmly screwed against the transistor, which was on the inside.
With every attempt, my Dauphine ran nicely in the beginning, but stopped definitively after some kms. Every time, after restoring the old situation (in which I am an expert now…) the engine ran without problems.

What can be the cause for this?
Has the power transistor been overheated the first time (first mounting was completely inside the box) and does this now cause the problems every time?

To be sure:
I checked and rechecked and finally desperately again rechecked the orientations of diodes and transistors. These are correct.
I checked for short circuits in the soldering. I can lead a thin screw driver in between every two soldering points next to each other, without feeling any relief.
The mica isolating film is between the cooler and the power transistor. The screwing connection of the cooler on the transistor is firm (I dare not screw it more tightly).
I removed the contact thread between breaking points and the bobine and I removed the condensator, present in the engine.

Please, who gives me the answer?

Edit:
P.S.: Of course I replaced the necessary resistors for the ones needed for 6 V operation.

2

Even though this is quite old post, I will comment it as it is useful info on the general level too.

The fact that the module has worked means that the problem is not likely an error on the construction of the kit. Components are placed correctly because it worked.

Power transistor needs cooling and it may overheat if the cooling is non-existant or insufficient. This has probably happened at first time when the kit was installed completely inside the box and therefore the power transistor could have been damaged.

TIP162 datasheet describes that maximum operating junction temperature is 150 degrees celsius. In closed box that could have been reached.

The kit is not expensive; buy a new one, assemble it carefully according to instructions and install it correctly and see what happens. I think it is the easiest way to proceed since the problem is in the kit and original system works. and remember the required modifications for 6 volt system.