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MG MGB Technical - Rewiring early B

I am about to rewire an early B.

1. Can I do the dashboard without removing it (i.e. is access good enough from the sides, through the radio hole and by the gauges to get my hands in and connect everything.

2. Where does the wiring to the rear lights and petrol pump run, if O know this I can minimise the amount of interior stuff that I have to remove.

Thanks
Dominic
dominic clancy

Dominic - If I remember correctly, I ran the harness in our 66 MGB with the dash out, getting it all tied in place and the wires sorted, then put the dash in place and wiring all the individual items through the holes in the dash. There are still some places where you have to lay on your back with your feet in the air to get some stuff connected. All the wiring to the fuel pump, fuel level sender and the lights in the back run under the car, with the wires for the lights entering the trunk through a grommet at the right front corner of the trunk floor. Nothing is routed through the passenger compartment. Cheers - Dave
David DuBois

Dominic, the dash wiring goes through the fire wall into the engine bay where it connects with the front, rear & engine component wiring.. This might be a good time to run the wiring to the rear of the car inside the cabin. Along the RH side of the trans tunnel & out of the rear end of the cab brings the loom close to where it would be if routed under the floor as original. It just gives the the most vulnerable part of the wiring better protection . I have seen this referred to as part of "winterising" the car. Barrie E
B Egerton

I'm really looking for answers about whether it is possible without removing the dash, as it's already mounted in a drivable car that is very nice apart from the loom. I know it is possible if I take the dash out!

I can see the grommet in the trunk corner, but haven't looked closely enough to see where the cabling went after that as it goes forward.

If the dash HAS to come out, are there any tips to making this as painless as possible?
dominic clancy

Dominic,
you can´t undo the dash without pain and tons of cursing. The (if I remember correctly) 6 or 8 small nuts that hold the dash in place on the shroud are a pig to get at and the "best part" are the 2 nuts between the instrument cluster and the indicator lights :-))
You can do the wiring with the dash in place when you take out all the instruments and the middle console. It also helps to undo the steering column to be able to lower it and so get at the bits between instruments and steering.
But still its a job for your worst enemy ……
Joern-M

If you have slim hands you should be able to get to the back of everything, it's probably worse getting to the nuts that hold the dash in as anything else. With the big gauges out first that helps with the rest.

The rear harness joins to the main harness in the mass of bullet connectors by the fusebox. There a number of clips and grommets securing it to the floor, personally I found replacing that more of a pain than replacing the main and dashboard harnesses on a late model car, which did involve removing the dash.

A pic of the two bolts that Joern refers to is attached.


PaulH Solihull

Im with Paul,it can be done and is easier on the early LHD cars as the loom does not have to loop back on its self like on a RHD car.
I would recommend that you lay the loom out in the house and label the wires together so when you do put it in place you can line the group of wires up with the correct switch.

Ste
Ste Brown

I am now well into the job, and so far it has been a great deal easier then the A I did a few weeks ago. The push-on connectors are a lot easier than all the screw connections on an A.

With the radio removed, I have so far installed the loom starting from the front of the car and have now reached the instruments and steering column, all so far without any pain or swearing at all. There is enough room behind the radio compartment to be able to manipulate the loom up from the wiper motor and across the heater box to the instruments (LHD car). The only things I have had to remove because they were in the way is the demister tubes.

Should get it finished tomorrow for about six hours work all in! I should add that this car is otherwise in great shape, the A was a bit ratty and all told took me about 40 hours to get everything that was broken fixed and working again.
dominic clancy

Which terminal on the ignition key switch is best used for the radio feed, 1,2 or 3 (original switch)

Thanks

dominic clancy

Have since realised that there is a special radio feed built into the loom. Is this always live or switched with the ignition (as it is a brown wire I suspect it is aways live)
dominic clancy

browN wires are always hot.
White are IGN switched, not fused.
Green are IGN switched, fused.
Since the radio should have its own appropriate fuse, it doesan't matter to the radio.
But On N, you can leave the radio ON, and listen while the car is OFF, but also can leave it ON and flatten the battery.
On G or W, you can't listen without the IGN ON, which is not good for coils, fuel pumps, etc.
Take your pick, or get an IGN switch with an ACC position = OFF, ACC, ON, START.

FRM
FR Millmore

Thanks Fletcher

The radio is only used when on the move, so I'll add it to the switched circuit from the switch

dominic clancy

MGBs from 1969 had an accessories position on the ignition switch that is typically used to power a radio when the ignition is off, but only when the keys are in and turned to the first position, the second position being ignition, and the third cranking. Initially with no factory, an in-line fuse would be needed for a radio. From 1971 this was factory wired in white/green to an in-line fuse under the fusebox, the colour then became green/pink and powered the heater fan, wipers and electric screen washer and was taken to a bullet connector behind the console for a radio. North American cars were slightly different in that they only got the accessories position in 1970, wired in white/green but no in-line fuse, getting the in-line fuse and green/pink in 1971 as above. This remained the case until rubber bumper cars, when the heater fan, wipers and electric screen washers went back to being powered from the ignition, and the white/green accessories wire was taken straight to behind the console with no in-line fuse, thus again radios would need their own in-line fuse. In all cases any 12v supply needed to retain the tuning memory would need to come from either a brown wire with an in-line fuse, or a purple wire (behind the console on cars with a courtesy light) which is already fused.
PaulH Solihull

Dominic said he has only three terminals on the switch, so it must be an early car with no ACC position.

FRM
FR Millmore

This thread was discussed between 24/11/2011 and 09/12/2011

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