Originally Posted by Montegue
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:

Originally Posted by Nickplus4
There are some posts somewhere on here from me on exactly the same issue. In my case it was the fly back diodes being under spec and failing to a short. Which blew that 5a fuse. I have replaced these with standard 4001 diodes and all fine. I popped some pics on here at the time and details of which diodes.

Cheers
Nick

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 frown

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 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.

Of course Rog is the real expert here, but hope my 2p'th helps.

Cheers,
Nick