Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Dash PCB-ectomy

I had the same on my s1 roadster but thankfully at the rad connector

That’s impressive Ken, thanks for the pic

I believe the blower can draw 15.1A max, so the MLX might not be best suited for continuous operation.

And of course once a poor connection has developed the situation becomes self exaggerating as lower volts to fan means you will likely leave it on high setting for longer!

Interesting though that Morgan used this connector as a standard fitment on the pcb. It appears to be rated at only 13.5 A max. from the data sheet, so think they were pushing it a bit?

Although I can accept that the reason for the plug to my fuel pump melting may have been the result of a dirty contact, I think the reason for the PCB Molex failure is that it was not up to the job.




Years before the fuel pump plug melted I had a fuel pump relay fail because the casing had melted




The molex failure is the latest in a fairly long list of components not being up to the job.

Not sure what current the fuel pump takes Ken but that Econoseal connector has a contact current rating of only 10 amps max. The pump is however fused at 15 amps!

The fuel pump in my car (a 2005 Plus 4) is from a MK3 Mondeo (2000-2007). Ford use a 15 amp fuse so probably not surprising that the Econoseal connector melted.

Something else for anyone having fuel pump issues to watch out for. 🙄

Such things happen every few years at the MMC. When/if I hear of them, I list them for posterity. The company has not, at least in the past, done regular advisories to the authorities on such things as other companies do. Owners/dealers must find out about any and inform each other. They can then perform what is, typically, a quick fix to avoid sadness.

One of the earlier such issues is worth mentioning as it turns up often. It happened to the MMC when they adopted SPAL rad fans, otherwise a VERY wise move. The Production Department kept using the same relay, fuse and wiring as they had used with the earlier (whimpy) rad fans. The big SPALs have, comparatively, a much larger draw. A special wiring kit can be purchased from SPAL (or you can make you own if you understand wiring with parts sourced at the nearest factor) consisting of a BIG relay, 30 amp fuse and more potent wiring. Before the MMC figured this out, there was a plague of failed fans..which caused engine damage to non-alert owners who didn't keep an eye on the coolant temp gauge in traffic. The point is that many moggers of older cars switch (pun!) to SPALs or similarly potent fans, in a justified hope of mitigating their heating issues but forget to upgrade their way of wiring it in.

I shall put a note in the Plus 4 section to warn others. TY

gmg

But at least they’re consistent…

I only got 12A rated relays on my board Some lucky owners got 16A

PCB update…..

I must admit, this is a bit embarrassing. My PCB is functioning flawlessly now. In fact, it has been working ever since I replaced the faulty fog relay driver transistor. The issue was that I hadn't properly connected it up when testing out of the car on the bench.

Things took a turn when curiosity got the better of me and I decided to sketch out some more of the circuit. It turns out that the micro doesn't receive its cue from the sidelights supply on the PCB to enable the momentary fog switch’s relay latching routine, as I had initially thought. Instead, its uses a single 'common headlight supply' directly from the column switch with a resistor in series directly into the micro. A feature I confirmed by probing my spare Disco 2 column switch, as it wasn't something I could deduce from the circuit diagrams. Thankfully a simple fix on my test setup. As soon as moved the supply to pin 5 instead of pin 4 on the 15 pin header it burst into life with the relay clicking and latching. So now my PCB is fixed, should I ever decide to sell my car, I can easily revert it back to its original state within a couple of hours if necessary.

I hope this will be helpful to anyone in the future with rear fog issues. It seems that this fault is not uncommon, as I have seen similar reports several times on the forum. The 2N3904 transistor appears to be yet another weak point, but looking on the bright side, there is a positive. Yes the introduction of these PCB’s into our cars is a bit of a nuisance. As discovered, a shot 15 pence tranny can be a real headache come MOT time. However, these older 70’s tech double sided PCB’s with discrete components are still relatively simple and as proven, can even be fixed by somebody with a schoolboy knowledge of electronics. It’s the next generation of multilayer boards with surface mounts that I fear will be the real spoilers, they will be an order of magnitude more challenging….

Working again. The off state and the on state with relay latched on.