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MG MGB Technical - Electrical Panel


I previously re-wired the fuse block and relays to behind the dash on my 74.5 MGB. I stayed with the orignal fuse/wire location with the addtion of a 4 more fuses.
Now I would like to clean this area up and make up my own fuse panel incorporating all the relays and the fuse block onto one board.

I have found a fuse block which looks interesting but I am unable to determine if it will work

For example with the 75MGB schematic the drawing show fuse #4 where all the brown wires come into one side of the fuse and the purples are on the other side. This makes perfect sence to me.

But looking at the Centech fuse box there appears to be only connection per fuse. How does that work. Will it work for me?

I don't want to re-invent the wheel but would rather keep the 4 basic MGB fuse systems the same for ease of trouble shooting.

Thanks any advice/input


Bruce -
Are you Bruce Mills? If so I thought we had fixed this thing!

I use a common stud input six fuse output block from Advance Auto or similar. By Buss. Located right behind the stock fusebox, you need a couple of shims becayse the "flat surface" is not quite big enough. Relays belong near the load, eg, for headlamps, on the rad support.
See pic.


FR Millmore

Send me your email and I will send the written description.
Behind the dash is the wrong place for relays, unless they are feeding things behind the dash.
The single stud feed box has the two original N wires, plus a fat Red since I was still getting voltage drops. All P and relay feeds are off this.
OE box has everything else. The single feed boxes are a PITA, you have to jumper the feeds to get multiple fuses off single feeds, and you also only have single outputs.

This pic shows the headlamp relays where they should be.


FR Millmore

Yup Bruce Mills, one and the same. I had to change my log in name for some reason.
And yes adding the ignition relay did solve that problem. But with the knowledge I gained from that experience and others I now want to to build my own fuse block as well as to clean up the mess of wires behind the dash.
I currently have hi beam, low beam, starter, ignition, horn, passengers door, drivers door, trunk (shaved handles)and cooling fan relays. I am going to add a relay for the fuel pump as well for a total of 10. In addition I am going to incorporate the turn signal flash and the hazard flasher to the same board. some of which is already incorporated in the Centech fuse box.
There is a lot of controversy over the wiring of the headlights, should they be fused or not. For many years I ran them direct. When I moved the fuse box and relays behind the dash I fused them. When I was having the last major electrical problems (which you and Paul were so kind to help me though)I was driving along at night at very low speed and the lights failed. Not much fun and could have been deadly at 70+. I am going to fuse the hi beam and low beam separately for a total of 4 fuses for the headlights. Then there will be no way I can ever lose both hi beam or low beam and give me the security of being fuse.
I realize he relays should be close to the item they are operating but I am sure you can understand from the picture why they can't go in the engine bay.

As I look at the Centech panel along the edge of the panel, it looks like there is a spot for 2 wires to each fuse?



Man, that is some kinda old school clean!
I'd rather have stuff where I can see it though.
Where exactly was your headlamp failure? You can see that I fuse the feeds for the H & L relays separately (PW & PR). But it still all comes down to the light switch, unless you find some multipole version.

I really hate useless but flashy websites! Centech say "lugless connectors allow you to wire your vehicle without using clumsy electrical terminals." That might mean that they use Eurostyle setscrew connectors, which you can put multiple wires into. They also say "heavy duty stud feed brings power in", which usually means that everything is powered by the panel, hence you are SOL for IGN fed circuits. Some manufacturers give you two stud feed inputs, and you can cut the bussbar between them to give split feeds.

Call them up and demand some info and a useful pic or three.
Or look up Bussman's catalog. Or go to a junkyard and get a relay/fuse panel out of something with lots of electrogizzies. like a BMW. They have dozens of relays and fuses, and you can soon figure out how to reroute the wiring on the back to do what you want.

FR Millmore

Actually since moving all the stuff behind the glove box (with the exception of 2 years ago) I haven't had to access the electrical system too often.

If I remember correctly it was a ground problem with the bullet connection up front by the headlights.

From my problem a couple of years ago I had gone from one end of the car to the other cleaning (repairing as needed ) and using di-electric grease on every bullet connector. Guess that one did not get pushed in far enough.

The wrecker was my first thought but our one and only wrecker in my arae is too far away to get to after work and he isn't opened weekends. Taking time off work to save a few bucks quickly racks up the cost and before you know it, it is cheaper to buy new. Life in a small Coastal town.

Thanks for the ideas. I will contact the company direct and see what they have to say. The item isn't cheap and before I hand over that kind of money and have it shipped international (I am in Canada) I WANT to know EXACTLY what I am getting.

Anyway thank for the info. Have a great Christmas and all the best for 2010. I am off to check out Bussman's

Bruce Mills

So the failure had nothing to do with fuses, but with sloppy work and poor design giving a single critical ground point connection. I run the light and fan wires to dedicated grounds on fender bolts on both sides, and also pigtail to the harness grounds at those points. You can see the RH one in the light relay pic.

Thing is, you can get all sorts of stuff off cars that you can't get in all the catalogs on earth. Look at various operational cars to find something that suits and order one from a junkyard if need be.

FR Millmore

"I had to change my log in name for some reason"

When enforced by the webmaster it's usually when you have copied and pasted the URL of a web page on this site to another web page somewhere i.e. message board or your own site. If you were logged in as yourself at the time this URL includes your login details, and if Google indexes it it allows anyone to log in to this site as you. Yep, BT, DT.

Not very keen on that metal cover of the Centech unit, doesn't look to be much to prevent stray strands of wire or whatever bridging to the fuse spades.
P Hunt

Paul it allows anyone to log in to this site as you....That is what I was told, was that someon was using my info to log on to the site. So that is very possible what happened.
There are other MGB sites I follow and it is very possible I copied and pasted the link to provide another MGB enthusiast with a link to some information.
In the future I will not log on and then copy and paste the link.
Thanks Bruce
P.S. good comment re "doesn't look to be much to prevent stray strands of wire or whatever bridging to the fuse spade"

I gave them a call and the Centech panel will not work for the MGB without re-designing the MGB electrical system. More than I wanted to get into.
My understanding is with the Centech main power is supplied to the fuse panel and individual wires go out the various components from that.
Where as our MG's, the power is supplied from a variety of sources.

Have you talked to Advance Autowire to see if they can sell you their power block panel without any wiring?

They do have an auxiliary fuse panel. Maybe you could use several of them?

I am installing one of their looms now and it's pretty substantial! All the wires are much thicker than stock. Relays for everything and modern fuses.

Since my car is customised and has non standard gauges it was perfect for me doing everything from scratch. Bit job though. Has taken me several days so far and I haven't even started the behind the dash wiring.

Simon Jansen

Actually Simon that is where I got the idea from. Custom Wiring For MGB V8 conversions by Dan Masters(2002). I did contact them about a year ago asking if they would sell just the power block but they never got back to me.
Dan makes it seem so simple in his article that now I want to build one to my specifications.
I like a lot of Dan's ideas but I need more relays and I want to use 2 power terminals. One from the alternator to feed 1/2 the relays and one from the starter to feed the other 1/2 the relays. A third terminal (actually a ground terminal) will be add to
the panel as well.
Dan even provides a parts list including suppliers but since the article is now several years old I am checking into the availability of newer components which suite my requirements.
I am currently trying to find a small fuse box with a minimum of 10 fuses.
I have located some relays which are @5/8 wide instead of 1". They still have to be totally checked into.
After all, isn't souring the stuff and learning about it 1/2 the fun!!!

Bruce Mills

Bruce, I am not sure Dan is involved now. I think there were some changes there and someone else has taken things over for them now so might be worth contacting them again.
Simon Jansen

There's a kit car supplier over here in the UK who sells this. I don't know if it's any good for you.
Mike Howlett

This thread was discussed between 23/12/2009 and 24/12/2009

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