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MG Midget and Sprite Technical - Frog Rewire Loom Question

I am rewiring my Frog which currently has a homemade-looking loom comprising it seems of about three colours!
I have purchased a proprietary loom which comes in a rear section, front lamp section and a main section which picks up from the instrument panel and also makes the link to the other two pieces.
I just want to check that the connection between the rear section and the main loom takes place in the engine bay. The position of the large grommet on the loom would seem to suggest this, but this means I have to thread the end of the rear section loom through this grommet as well. I don't think the grommet has slid down the loom to finish up the wrong side of the rear lamps/fuel level and rear indicator connections.
Unfortunately the rubbish loom I am removing gives no reliable clues.
Graeme Williams

I only know there is a diagram for the 1500 might help it is in three parts rear

mark 1500 on the road Preston Lancs


mark 1500 on the road Preston Lancs


mark 1500 on the road Preston Lancs

The connection between front and rear looms is in the cockpit, just below/behind the RHS of the dash.
Dave O'Neill 2

On later cars BL put in line fuses on the brake and light wires going to the rear section. These fuses were located where the rear section connects to the main harness. This prevents the wires from melting in the event of a short in the boot area. Also one of the connectors going to the voltage regulator has a fin on it. You may still have this piece if any of the original wiring still exists. It is not critical but no longer available. Your new harness has a regular spade connector. Originality is the only factor.
J Bubela

Thanks Mark but the loom looks totally different - no multiway connectors.

JB: none of the UK sprites/midgets (don't know about the 1500) had additional fuses beyond the two fuses in the fuse box. THat said, I am planning to add fuses to the lighting circuit and also relays for the headlamps.

Dave: that means the front loom would have to be pulled through the grommet along with the middle section. my problem will boil down to the fact that the "rear" connectors on the middle (main) loom are the wrong side of the grommet and probably would be difficult to pull through to the footwell side.
Graeme Williams

I have a Sprite Mk1 wiring diagram if it would help you. I can scan it this afternoon sometime.


Greybeard - thanks but I have that. Unfortunately it doesn't relate physical positioning between the diagram and the car.
I have actually redrawn it with the extra relays and fuses and labelled up the loom sections.
Graeme Williams

You could take some pictures of any of the Frogs at the Masc meet this Sunday.
Alan Anstead

Does this link to the Moss catalogue wiring parts list help?<>
Peter Blockley

That link doesn't work, but you can follow the path to the page. Alternatively, here is jpeg version.

Peter Blockley

Will do that Alan although I think I have concluded the best place for the junction is in the engine bay up against the firewall. THe reason is that although it carries connection to the rear end, the front end lighting is also at the same position. To remove the bonnet these will need to be unplugged so in the engine bay is going to work best.

Peter: thanks for that. I found that earlier but the critical point isn't clear enough.
Graeme Williams

Hi Graeme,

I did a loom in a frog last year.

The rear harness comes thro the big grommet adjacent to the rh bonnet hinge and it all connects there, together with the bonnet loom.

Fuses and relays are a great idea for the headlamps, but do ensure each filament has it's own fuse, ie 2 dip and 2 main. That way if the fuse blows you're not plunged into total darkness!

The 1500 did have the sidelamp circuits fuesd left and right via a 4 way fusebox. Tho that didn't include the panel lamps, always a good idea to add a line fuse to that circuit behind the dash.

Don't understand the comment about a line fuse for the stop lamps on US spec cars? The stop lamps were always fused prior to the switch via the green wire off the fusebox.
SR Smith 1

x2 Steve on the relays and separate fuses. That's the advice you gave me when I installed relays in my car. I consider it to be the best mod I have made, so thanks.

If you're using crimped connectors, can I suggest you spend a bit on a proper ratchet-type crimping tool. The cheap ones that come with terminal kits are worthless IMO. They can actually cause localised hotspots in the wiring.

Also a tin of Scotchkote. The stuff is unbeatable for insulating joints and preventing corrosion.

You are correct about the location of the connections by the n/s hinge.
I have e-mailed you about 'Old Boys'
Alan Anstead

Hi Greybeard,

It's my profession and have seen some accidents looking for a place to occur over the years as a result of ill advised "modifications".

Glad that helped, did the same on my car years ago.

Personally I never use crimped terminals on classics. Get a decent sized soldering iron and some heatshrink sleeving. Looks far better as well.

proper crimping tools and the oe type terminals with seperate sleeves are all available on line from companies like Beal Uk.

Regards Steve
SR Smith 1

Oops! That should be offside hinge!
I think Graeme invested in the correct crimping tool when I too suggested the soldering iron.
Alan Anstead

Steve - I know it's your vocation. Re-reading my post it sorta looks like I was trying to teach my granny to suck eggs! Sorry about that. My point was about those horrid crimping pliers but not aimed at you.

Apologies for the badly written post.

In general I also prefer soldered joints with heatshrink sleeving (two layers - the outer adhesive lined), but it's not always practical.

When I make up looms for boats I like to use Amphenol severe-service bulkhead multiways. Utterly bombproof but they're a bit OTT for cars!

Just for reference in my job I routinely make up cable looms for ROVs that isolate power supplies up to 10kV in depths of 3000 metres or more of salt water. That explains why I'm so anal about insulation and corrosion protection lol!

Talking about accidents waiting to happen - in about '78 or '79 I went to a lady's house in Nottingham to fix a lavatory cistern and found a small mains powered portable TV wedged between the bath taps with an extension cable running under the door. What could possibly go wrong with that?


Thanks for you comments.

Steve's comment "The rear harness comes thro the big grommet adjacent to the rh bonnet hinge and it all connects there, together with the bonnet loom." ties up with what I concluded, which is how the loom has been made.

With regards to fuses, I can see the brake circuit is fused but there is the usual lack of fuses on virtually everything else. I posted a thread a while back trying to discover why the lighting circuits weren't fused as a matter of course and wondered whether this was a safety issue associated with loss of headlights if a fuse blows. I have fuses to each relay and fuses to the side lights, panel lights and the dip-switch.

(Just thinking about the dip switch fuse. If that failed it would result in total headlamp loss; need to rethink that one)
Graeme Williams

Hi again,

No probs greybeard, i didn't for one second read your post like that!

I'd rethink your fusing Graeme.

To be fair the only unfused circuits are the lights and ignition feed to the coil. The wipers, instruments, gauges, horn/s and stop lamps are all fused.

Best and safest way is to fuse the headlamps after your relays via 2 dip and 2 main fuses.

As you say, if the fuse in line to the dipswitch blows you have zero h/lights, even if you have the presence of mind to swiftly bang the dipswitch!

A single line fuse in the sidelamps is fine and a good idea. The Morris Minor used this system, dunno why other BMC cars of the 60's didn't adopt the same arrangement.

Most Fords of this era had no fuses at all, the cortina had a single line fuse to the indicators only!
SR Smith 1

Steve: the problem with fusing after the relays is the loom has a single wire run for each headlamp pair so although I could fuse both dipped lamps together, fusing them individually is much more of an issue. I would need to break down the loom and run four single wires rather than the two wires which currently "double up".
The most significant issue is the fuse I had intended to put in the feed to the dipswitch. If that blows both head lamps pairs are out!
Graeme Williams


Yes I realise that Graeme.

No need to run 4 new wires though.

Best way is to run a new section of loom into the bonnet to the rh headlamp from your new fusebox and use the existing wiring for the lh lamp.
SR Smith 1

Are you a Kent Masc on Sunday? Probably easier to pick it up there rather than take up everyone else's time here.
Graeme Williams


Nope, yet again it clashes with something else Graeme.

But give me a ring on my business mobile 07760 176926, happy to advise.

Regards Steve
SR Smith 1

This is the way I solved the relay and fuse problem. Be aware that the diameter of the original new loom and the connectors is so that the resistance diminishes the current and voltage. The H4 bulbs will give half the lumen of an 2.5 mm copper wire without connectors. Also pay attention to thicker earth wires.

give all old fashioned connectors some vaseline.

Flip Brühl

That's fine Flip, but if either one of those line fuses blows you lose both beams at the same time!
SR Smith 1

This thread was discussed between 17/01/2016 and 18/01/2016

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