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

As is evident, PCBs and many other similar devices and assembly methods do not improve or advance automobiles. They merely cut down labor hours and the needed expertise required to assemble cars. All manufacturers are currently trying to save money by such shortcuts. It is part of what economists call hidden inflation. I wonder if the Works could offer an option of ordering a car without them.

PCB et al cancel out much of the brilliant rationale behind the development of multi-fuse boxes(after 1986ish for Morgans) along with Lucas wire colors (which I think are pure genius and guided the world in this area). Sadly, by using them, they lay an impossible new burden of diagnosis and repair on owners who have considerably less expertise and resources than the manufacturer. They prohibit roadside and dealer repair along with owner interaction. The best idea I can think of is to remove such devices and bear the cost of the extra work that should have been done originally.

gmg

Of course there's nothing wrong with progress, if this wasn't the case we'd all still be living in caves instead of houses, and heating our caves with open fires instead of the central heating boilers we use today.

Talking of central heating boilers, I have an old Potterton Profile in my house that must date back to the mid 1990's and after 25 years of reliable service the control board gave out, so I fitted a reconditioned board for £70 that apparently incorporated some improved components to ensure this time it would last even longer than 25 years, which to my mind was pretty impressive anyway!

The components that fail on a Potterton Profile control board are clearly well understood as the engineer who sold me the reconditioned board upgraded them, in a similar way there seems to be a suggestion on TM that the Morgan dash module PCB fails because the diodes used either aren't the best quality, or simply were not correctly specified to cope with the peak inverse voltage spike (Back EMF) produced by the relays.

I made my electronics engineer aware of this when I dropped off Monty's board for checking over and repair, I encouraged Richard to make his own diode value calculations rather than just replicating what was originally used as it's very possible they were underspecified from new?

Let’s see what he reports back with, who knows if I'm lucky, perhaps like my Potterton boiler control board my Morgan dash module will come back better than new and with the original fault removed for good?

Dave.

BTW, Monteque, I enjoy your posts. Thank you for them.



It depends on the definition of "progress" one chooses. The earlier variant of capitalism I was born to, maintained that progress was a more functional widget, better suited to purpose. At that time, aside from the risk of new latent defects, progress meant "better". These days goals have changed. I do not think cutting the man-hours to increase profits while degrading the widget and making it less owner/repair friendly is progress. The causes of climate change massively increased profits but I do not see climate change as progress. Actually, your evident enthusiasm interacting with your Morgan (which I share) would be more effectively satisfied if you still could use the brilliance of British wiring colors and multiple fuses. They have been made largely ineffective by PCBs. BTW, I have great hopes for technology. I follow the new good stuff that might save us all each day. Proft-progress sends us in the other direction..possibly back to caves.


Yes it is impressive! However, I note that a better fix was readily available, waiting in the repairman's bag. The weakness had been diagnosed and an inexpensive solution was already at hand. This was not the case with your Morgan and the others similarly setup. I could point you to other time-saving mods that have made life for owners more difficult and the cars less reliable, not that they haven't improved in other areas.


But do YOU personally understand your PCB? Can you diagnose all electrical anomalies and repair/replace roadside with it or is a specialist necessary? And what will be these answers 30 years from now? BTW, this is ironic for me as I often argue strenuously to this day) about the lack of common sense in the old 2-5 fuse cars and the use of uncoded wiring as replacement. Seems I am caught between two extremes and always seeking the most functional, reliable and owner-friendly. (wryly)



Are these changes going to have your car leave the template/friendly family fold of other Morgans of your year? I have found that the glue that kept the community together for a century+ is the commonality of our templates. If you removed the PCB and re-wired as before, you could, of course, join (re-join) many, many 1000s of your brethren. And there would be no effect on the car aside from it becoming easier to diagnose and repair for ever more and everywhere.

gmg

Dave: regarding point number 6 above, if you take a close look under the driver seat, you should see a pair of wires that run from the seat belt and disappear into the transmission tunnel. They are fairly long to allow the seat to slide back and forth and also have a flimsy plug and socket to enable disconnection if ever the seat has to be removed.
It is very likely that either the plug and socket have pulled apart, or the cable has been damaged by being caught in the seat runners.

Excellent Doug,

Super helpful as always

Many thanks, Dave.

To conclude this one, here's the repair completed by my local electronics engineer for £36.00



As we can see the burnt track has been neatly bridged.



After studying the relay Richard chose to fit an uprated silicon diode in a slightly higer value.



And here's a close up of the uprated silicon diode next to the original, it does look like germanium diodes were originally used on the board.



Germanium diodes have higher reverse leakage current and that increases with temperature, another drawback of germanium diodes is their low reverse blocking voltage that limits its operation to low voltage rectification only. Conversely, silicon diodes can work reliably up to 170 degrees celsius, and the reverse bias saturation current is very high. The forward break-over voltage of the silicon diode is very high, losing roughly 0.7 – 0.9 V with the silicon crystals having the capacity to withstand high temperatures, moreover, the forward voltage drop for silicon diode junction is low.

In summary, silicon diodes are more temperature stable, less leaky and generally way more robust than the germanium diodes it looks like were used on the Morgan dash module PCB, Richard clearly felt switching to a more robust silicon diode of a higher value would offer superior reliability and longevity.

I collected the repaired board from Richard on Friday, fitted it on Saturday and tested it yesterday.



I'm pleased to report all my previously missing switch illumination and tell-tale warning lights have returned, and the speedo continues to work perfectly, for those following this post you'll know it was the loss of my speedo that started all this. However, I'm currently running with one fan speed only as going to fan speed two will blow the 5a fuse 4 for the dash module, I'd say this will be an issue with the relay for fan speed two rather than the blower motor itself. The good news is a Morgan heater is a powerful thing especially now I'm able to open the heater valve fully (more on this later) and fan speed one is more than capable of moving all that hot air, I conclude the loss of a second fan speed is more or less irrelevant.

What's important to me is my speedo works, I've got my indicator tell-tales back, my headlight and dip beam tell-tales have returned and my switches illuminate as they should. Back to the heater, with the dash out I took the opportunity to free up the partially seized heater control mechanism that from day one since I bought Monty has been impossibly stiff to operate, it now has the full range of movement from off to a fully open heater valve that with fan speed one gives furnace like cabin heating performance even when driving with the roof down.

I also removed all three gauges and polished up the bezels which came up like new, located an annoying rattle that actually turned out to be a loose handbrake lever button, and generally made sure all the connectors were good.



Overall I have to say I'm not very impressed with Morgan's dash module PCB, I would not be at all surprised if I suffer further diode failures, fortunately dropping the dash to remove the PCB is easy and now I've learnt the job the next time will be even faster. Having Richard just up the road is also a real bonus, he repairs all sorts of electronics locally and has a very fair charging policy.

As I understand it Morgan was charging £600 for a replacement PCB which is insane and many on TM have reported multiple failures, and of course these PCBs are no longer available so these days the failed one must be repaired. Moving the relays off the board as shown to us by Rog in his excellent post is definitely a good idea, it’s certainly one way to upgrade those weak germanium diodes to something better, but I can't help feeling the ultimate solution would be to delete the PCB entirely as offered by Luigi Borghi with his custom dash module option.



However, given how easy it is to access the PCB and as it only cost me £36 to have it repaired and uprated locally, this proved the best option for me. If it fails again I'll have Richard upgrade all the diodes, and if it fails a third time after that I think I'll be investing in a Luigi Borghi custom wired dash module.

Dave.

Dave, Pleased to hear of success and useful info about the diodes.
Have you checked out the seat belt light yet?
Doug

Hi Doug,

I had a brief look but couldn't see any wiring at all, and being honest a working seatbelt warning tell-tale is not high on my priority list, but I'm grateful for the pointer and I expect I'll find some time to look at it next weekend. There are a few elements like this that still require my attention, however, the results are overwhelmingly positive with the £36 repair improving the situation considerably.

Let's look at the results:

1 - No illumination of the fog light switch - Rear fog light still works

Result: The rear fog light continues to work but I now also have switch illumination, and when I press the switch its illumination goes brighter it indicate the light is on, I didn't have this feature before despite the fog light itself working just fine


2 - No illumination of the heated screen switch - Heated screen may not be working?

Result: I now have the switch illumination back, but I'm still unsure if the heated screen actually works? The switch illumination certainly does not go brighter when I put the heated screen on, I plan to test it next weekend with my infrared thermometer gun


3 - No indicator tell tales - Indicators still work

Result: Indicators remain working and both tell-tales have returned


4 - No headlight tell-tale - Headlights and sidelights still work

Result: Headlights and sidelights still work and the green tell-tale now works too


5 - No high beam tell tale - High beams still work

High beams still work and the blue tell-tale has returned


6 - No seat belt tell tale - This light never worked in my ownership

Result: As above, this still needs looking at, as pointed out by Doug it's probably just a broken wire or possibly something as simple as the connector is disconnected. Techniques Morgan would have had my seats out to fit the rear springs so perhaps they and those before them may have simply failed to connect the wires? Anyway, I'm not too stressed about it as I'm fully aware if I've put my belt on or not, and I always check to make sure my passengers are buckled in too.

Less positive is it does seem if I put the blower motor on its second high speed fuse 4 will blow, as we know this dash module fuse is rated at just 5a and I'm loathed to play about with higher value fuses again as this is likely to cause another board failure. However, disappoingtly since putting everything back together I now seem to have lost my hazzards, hopefully Richard can fix this when I can be bothered to pull the dash down again, at which point he can test the fan speed two relay and sort the heated screen if it proves not to be working.

So it's still a bit of a work in progress but I suspect some more upgraded diodes and maybe some more tracking bridges will fix these last few elements, overall while I still do not have 100% perfect functionality of everything I would still consider the very cost effective repair to be a great success.

I am also delighted to report since I put everything back together I seem to have inherited a free air conditioning upgrade! No compressor, no condenser, no trinary switch and no additional wiring was required... but out of the blue comes the never seen before icicle tell-tale when I put the heater fan switch to position one with the aircon switch on too

Re: the air con switch/ icicle light…mine has always done that so think it was a standard feature!
The heated windscreen…mine once failed quite early on its life and I found that the problem was a couple of bullet connectors up near where the windscreen wires exit the bulkhead; they had never been soldered and the wires had simply fallen out!
So worth checking when you next remove the dash.

Thanks again Doug,

It's helpful to know what functionality others have, I certainly have never seen that icicle before on Monty so I became quite excited when it popped up

I'll also check the heated screen wiring when I next drop the dash, in the mean time here's a final overview of where I'm currently at following the PCB repair.



In this video you can hear me referring to the hidden battery disconnect device I fitted that also doubles as an immobiliser and alows me to leave the car in the garage with the battery disconnected which is good for a number of reasons, personally I think it's a more effective security feature than the Ford PATs system I lost when I changed to the excellent EMU Black plug and play ECU.

Overall I'm happy with the progress so far, but I've now decided to put my tools down for a while so I can return to simply enjoying Monty.