Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Dreaded PCB Stikes Again

Earlier cars have variants of the awfully fragile and exposed PCB as an early form of BCU. This allows the possibility to replace with basic relay control as Rog has done, although I believe without any timers. I think I'm right in saying the logic required within the PCB to provide the momentary switch latching is lost in such case hence need to replace with simple toggle switches. Perhaps Rog could confirm but if so it appears that Borghi offers similar as his version appears to employ retro toggle switches as well.

That feature remains with the toggle too. The fog light will not remain on if you leave the car with the side lights on as the fog supply drops out when the ignition is turned off.

I've also just found the following post that seems to point to a common link between the blower motor and these multiple PCB failures

https://www.talkmorgan.com/ubbthreads.php/topics/612561/all/pcb-fails-for-the-fourth-time

This comment has also got me thinking:


TBH rather than relying on a repair of the burnt track I really need to understand why it failed in the first place, or it'll likely just fail again

In the above post Gambalunga talks of four PCB failures on his 2012 Plus 4 before he went to an old school relay solution, Monty is a 2012 Plus 4 and my failure also arrived at the same time my blower motor went on strike, the similarities are hard to ignore.

At the time of failure I also blew the fuse for my speedo and ignition warning light, however, once the fuse was replaced the speedo and ignition warning light did return. But sadly I was now left with no illumination in the fog light and heated screen switches, although in my case the issue is just switch illumination as both the switched devices themselves remain functional.

This is what I was left with:

* No illumination of the fog light switch - Rear fog light still works
* No illumination of the heated screen switch - Heated screen may not be working?
* No indicator tell tales - Indicators still work
* No headlight tell tale - Headlights and side lights still work
* No high beam tell tale - High beam still works
* No seat belt tell tale - This light never worked in my ownership

Oddly I still have illumination in my hazard warning switch?

Like I say, I’m keen to trace the true source of the fault rather than just have my local electronics engineer repair the burnt track, could there be something in the fan relay flyback diode theory?

Hi Dave

Borghi has now been taken over by Romeo Ferraris: https://www.romeoferraris.com/it/concessionaria/concessionaria-morgan-motors
I believe Luigi is still in the business and I don't know if he sold to, or merged with, Romeo Ferraris. In any case I imagine that he is still doing these conversions, which can be done without replacing the dash. Part of the problem was that the heater fan is actually wired in reverse to the normal logic. That is to say it is constantly powered and the control is on the earth side, unlike the rest of the system.
After several years and many thousands of kilometers I have had no further problems.
Unfortunately you would have to take a trip to Milan to get the job done. When someone else had a dash replaced he did offer a loan car for use while the job was done,
It is a good excuse for a holiday in Northern Italy (read Lake Como, good wine and food etc.)

Hi there,
So looking at that track and diode it does look like you have a similar problem as I did with the heater fan motor. My diodes failed to a short, so caused a fuse to blow each time. I assume that a fuse blew when you lost some of the functions? Did you try a larger fuse? Or was it quite a high current fuse anyway? That diode failing and a decent current through that track could have blown the track. I suggest just checking the resistance across the diode (check with the probes the right way round so that you are not forward biasing the diode) - it is in parallel with the relay coil so you will get quite a low resistance if all is well, or a dead short if it is blown. If it is blown you could try replacing it with a common or garden 1N4001 and fix the track with a bit of wire.

I'm not sure if you still have heater fan issues? I would ensure D6 and D7 are also changed at the same time to prevent that issue raising its head.

What I don't understand is why this only affects some cars and not others - unless it is to do with the a voltage regulator or somesuch.