Hopelessly

Not in my most daring dream I would have thought that I spent a few hours this week with Rick Astley. But I am not talking about the English singer and songwriter. Nope. Even though the first lines of one his songs pretty much sum up my week:

I walk the wire every night
I can’t decide between wrong and right
I’ve lost control over the thing I do
Cos I’m hopelessly falling in love ….

…..with the idea of having a solid wiring harness for the Morgan (and MGB)

There is another Rick Astley. The one I am talking about is not only a fellow MGB owner – more importantly he is also the brilliant author of the book: “The essential Manual: MGB Electrical Systems“. A book that is mandatory for every MGB owner. And as you might guess by now: I unfortunately did not meet Rick Astley in personal – I just spent time with his book.

Due to work I currently don’t manage to get to the garage during the week. But as I took the wiring harness out of the Morgan and have it at home right now – I was able to find a few hours to unwrap the protective tape and work on the updated wiring diagram. And even though the Morgan and MGB wiring have several differences – Rick Astley’s book proved to be super valuable for the changes I am planning. For every system he describes the flow of the current starting from the batteries to the electrical load. This includes the differences in the various MGB cabling variants as well as improvements – such as relays.

When I removed the wiring from my Morgan during the initial restauration – it only had one connected relay for the aftermarket horn my father added. A second one was dangling in the loom behind the dashboard and was just connected to earth. The replacement Autosparks loom I bought did not fit the 1984 diagram – it was closer to the 1988 diagram found on GoMog. And according to this diagram, the 4/4 did not have any relays.

When I first worked on the Morgan wiring – I didn’t really think about the benefits of adding relays. But over time and while slowly getting more experience on the MGB and Mini wiring – I started to regret this decision. And after spending more time with Rick Astley’s book on the MGB wiring I am glad I took the loom out again.

The first decision I had to make is how many relays I will add and where to place them in the wiring. I am not a fan of single relays in the engine bay as I have them in Maggie. Preferably, all of them are in one fuse/relay box. But how many fuses and relays will I need? The best way to get an answer to these questions was to break down the circuits and systems like it is done in the “MGB Electrical Systems” book. Then I looked at how much watt is needed for a system. If the required current is high – I will add a relay. I also considered that I will use LED light bulbs for the brake lights, indicators, and side lights.

The result is that I will have 6(+1) relays for: ignition, fan, horn, dip & main beam, and fog lights. The 1984 Morgan diagram as well as all MGB plans also have a starter relay. Looking back, I believe that this might have been the dangling relay I had behind the dashboard – which likely got disconnected when my father replaced the original dashboard (just a guess).

Powerdistribution to and fuse placement for the relays was the next topic I thought about. While at it, I will add two brown 6mm² (AWG10) wires from the starter to a “power distribution box“. This will be sufficient for 2x 40amp and the box can handle an input of up to 100amp.
Finding the maximum amps for some systems is easy:
– Revotec fan needs 12,5A max. (fuse 20A)
– Lucas LR6 sealed beam (fog lights) ~12amp (fuse 15A)
– Horn 40W ~3A (fuse 5A)
– Osram nightbreaker has a 60/55W rating for dip- and main beam. This is ~10amp per relay (fuse 15A)

The first of these three systems will not have a fuse after the relay. On the dip- and main beam I might add additional fuses for the left and right side. The ignition relay feeds everything that is attached to a green cable. For example wipers, washer, Instruments, Reverse, brake lights, thermo and a few other things. Some of these items will be grouped on one fuse, some will be on their own fuse and most of these only require a small 2amp fuse – especially when I switch to LED bulbs.

For the Morgan I bought a 16-way blade fuse box from MTA. For the MGB I already ordered two modular boxes – which each can hold 4 relays and 12 blade fuses. My first idea was to use both an replace the MTA box. But even if both variants are “just plastic boxes” – it quickly became clear that the MTA box has a much better quality. MTA also offers relay holder boxes – one for 4 standard relays and another one for 7 micro relays. Seven relays – exactly what I need !!! And these have the same size as the fusebox – which fits well beneath the rollbar. So, I ordered this along with the necessary Bosch Micro relays.

But I already had 4 holes for the old fuse box drilled into the bulk head. And in order to fit the two MTA boxes as well as the power distribution box – everything needed to be moved left for approx. 2 cm. Logically, I don’t want to the bulkhead to look like swiss cheese. Therefore I took a piece recangular steel pipe I had laying around, cut two 40cm long pieces which I attached to the existing holes. I then offset the holes for the MTA box and put in rivnuts to attach them. These holders will also help a lot now determining the right cable lenght. Some new MGB parts also found their way into my garage and I started to prepare the next round of items for powdercoating. More on this in the next post.