MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Wiring harness through firewall?

I just got a new wiring harness for my TD from British Wiring. It looks great, and the braided segment that should go through the firewall looks about the right diameter (1 inch) to fit through the the grommet in the firewall. BUT, there is a fat branch for the control & fuse box on one side of that segment and a fairly fat branch on the other side of that segment that should be under the dash (it will run to the starter switch to pick up the power). So how do I squeeze the harness through the hole? If it goes one way, one fat branch is in the way; If it goes the other way, the other fat branch is in the way.
Richard Greenberg

Put the grommet on the wire harness first, then feed the wires through the hole and finally work the grommet into the hole.
Jim Merz

A heat gun or hair drier can soften the grommet temporarily making it really flexible. If wires still won't squeeze through, do as suggested above and try popping the grommet out of the firewll and fitting it onto the harness, then soften the grommet if you have to and work it back into place.

Experiment with grommets off the harness first since it doesn't take long the melt the tape and grommet on the wires.

It is amazing the difference between a grommet at 50F and 150F!
Jim Northrup

Richrd, I taped the wires together with some mssking tape and than used siliconspay and pretty easily wobbled they bunch through.
If you making sure the seprate wires are put in th sequence that they will attach to the rgulator post, you can make it very decent. In a recent thread about thistopic I putted a picture (on a different pc now). Good luck, Huib
Huib Bruijstens

I think the new harnesses are a bit fatter than original, so you may have to enlarge the hole a little.
George Butz

The branch of the harness with the wires for the control box and fuse block is very thick, it branches perpendicular to the main harness and it is braided for about 1.5 inches from the branch point. I don't see it passing through the hole, even with the grommet out of the way. I will use all the tricks you have all recommended. I have a feeling I am going to enlarge the hole quite a lot. Any additional ideas?
Richard Greenberg

Richard, the last thing that I would do would be to enlarge the hole in the firewall. It's been a while since I last installed a complete harness and I don't have access to my car at the moment. Maybe I'm totally out of sync, but I'm wondering about the direction in which you are trying to move this bundle. Any chance that that bundle should simply (ha!) be located on the engine side of the panel and a leg of the harness should go down through the grommet into the cowl side? Bud
Bud Krueger

I always go the opposite direction that Bud just cited, but decided last time that I would try it his direction as the wire bundles seem to get fatter as the aftermarket is involved.

full picture set on my website. Look under electrical.

warmly,
dave
Dave Braun

Just remembered that I had the firewall of 'the53' down in the basement. The harness is still in placed, just cut off. I'm now convinced that the way to do it is to install the harness from the firewall side. I don't see how you could get that branch through the grommeted hole in the firewall. The branch that does go through the grommet, into the tub area is bad enough by itself, but it's a straight shot. BTW, there is a slippery substance that is used by electricians to pull cables. It comes in a squeeze bottle and is readily available at building supply stores. Here's an image of that area from 'the53':



Bud Krueger

I'm thinking that the outside braiding on my new harness may go too far along the branches to the control box, fuses and horn. I may try cutting back some of the outside braiding to make those branches go through from below. Or maybe I will try feeding the harness downward. I'll have too look at the size of the hole once have the old harness out. The car runs fine, so I don't want to take out the old wiring until I am ready to install the new. Again, any further advice would be appreciated.
Richard Greenberg

Dave Braun's web site is excellent. It is evident that the problem with my harness is that the bundle for the control box, etc. is loomed for a inch and a half out from the main loom, making a thick rigid perpendicular branch, whereas Dave's had all those wires free to lie flat going through the hole.

Question: When I cut back the extra loom cover, what can I use to prevent any unwanted fraying and unraveling? Should i smear on some glue or varnish?
Richard Greenberg

Richard,

Thanks for the compliment about my website. I think the outer braiding will melt under a heat source. You may want to test that theory and try a few swipes of a soldering iron to seal an edge.

My branches stuck out perpendicular too until I worked them hard to get the grommet through, for what it is worth. I would trim the outer cover as a last resort.

Now I'm wondering if I am misreading Bud. But my operation has always been to feed the entire harness through from the interior because the bulky wires for the turn singal relay, which on most TDs that have them, are located inside the car. The wiring for the rear of the car is relatively thin, except for the regulator. Also all the wiring to the fuel pump and other horn has to be on the inside of the firewall to exit on the RHS. I guess it is the only direction to go, unless you feed everything through the outside of the firewall and then over to the fuel pump side and out again! Whew!

warmly,
dave
Dave Braun

This thread has got me thinking about which supplier to purchase my wiring harness from. Little T came with a new harness purchased probably in the Seventies but it was wrapped in vinyl tape and I prefer the cloth so I ebayed it. I am sure there are many sources but which are the most recommended by the group. It seems that many have purchased from British Wiring so are they one of the most recommended?

Regards,
Rich
Richard Taylor

So I guess no response means eveyone bought their wiring harnesses from British Wiring?
Richard Taylor

I got my TD harness from Moss and am pretty happy with it. It's the one with directional signals but has the early "in the dash" (facia) headlight dimmer. Also clothcovered,
Bob
Bob Jeffers

Mine came from Moss, same layout as Bob Jeffers. There was no way in the world all of the wires/branches would fit throught the original hole without enlarging it a bit. Only concern I have with heat and lube is that if it is cloth covered, that will make a mess. George
George Butz

Richard,

I did mine without heat and lube, I also did not enlarge any holes.

My harness came from British Wiring, as I've mentioned in my website and here many times. I chose them because they offered me a customization for early dash with a dipper, late turn signal relays on the inside firewall, an extra long wire for the turn signal indicator for my buzzer, a late main beam indicator light for my late speedometer, and turn signal flasher on the interior side of the firewall. I also purchased proper ground, battery and starter wires from them.

It took 30 days because I hit the cycle with the British manufacturer correctly. The only mishap on my bundle was an easily correctible main head light beam wire. It didn't interface with the dip switch quite the way it should have. Unlike some of the Moss wires I've installed, the dash wiring was separate, except for the horn, ammeter, inspection light sockets and ignition to coil wires. Much easier to install that way.

I wired the charging regulator and fuses twice, once to fit the wires, and a second time to neat up the installation. Every bullet connector was soldered on, and all plain ends were tinned.

One thing I've never thought of before; the very early cars with nine post regulators have a slightly different wiring color (for example, horns), and don't need the extra brown wire for the fuse block, as it is incorporated into the regulator. I suppose you could ask British Wiring to solve these irregularities as well. It isn't hard to understand or see what should be done with a standard harness under those conditions. But following a single wiring diagram has its merits (I should talk, mine is a conglomoration of middle and late, but I kept notes). Sometime I'll write about my friend Mike, who customized his wiring harness with extra relays and an alternator. Trouble shooting that is fun, because there are about five ways to do all that, and he just did it on the fly and neither of us can ever remember what exactly he did from time to time when we look for a discreapancy!

Hope this helps.
dave
Dave Braun

I installed a Moss harness a couple of years ago and managed to get it through without enlarging the hole, but it was very tight. The method was to bend all the short wires for the fuse connections forward individually and laid them along side the harness - side by side. Then tape with a slick thin plastic tape, extending the tape past the wires for a taper. They then wiggled through. In my case the wires for the turn signal relay and the flasher unit stayed inside the bulkhead, so that made a difference. If they were outside the bulkhead it would definitely be a no go.
Dallas
Dallas C Congleton

Dave B my harness will have to be slightly customized as well. Since Little T is an early TD I do not have turn signals but plan to add them but do not necessarily require any type of indicator.

My dash has already been wired up by Craig Seabrook so not sure exactly what I need there plus I also have the early 9 pole regulator and the dash mounted dip.

I guess my best option is to go with British wiring so I can get the customization that I require which Moss could not do.

Check out this site. I have never ordered from Englishparts.com before but looks like this is close to what I need.

http://www.englishparts.com/products/WIRING-HARNESS-KIT---COMPLETE-NEW-HARNESS---LACQUER-BRAID--TD-TO-C18882--ADDS-TURN-SIGNALS--INCLUDES-EVERYTHING-NEEDED/7930/357-068.html


Regards,

Rich
Richard Taylor

Rich,
You have mail!
Dave Braun

Last I knew you could deal directly with the folks at British Wiring - http://www.britishwiring.com/ They were very accommodating.

Rhode Island Wiring Service (http://www.riwire.com/) is a great source. (The owner drives an MGB.) Bud
Bud Krueger

I thought I would reactive this thread to let you all know how my wiring harness purchase from British Wiring went. I first emailed and told them I needed a wiring harness for an early TD and I wanted to add turn signals. I believe the gentlemans name was Josh recommended I purchase the 590BB. I received the harness quickly but after stetching all the wires out it was obvious all the turn signal electroics would have to go on the engine side of the firewall so I called BW back up and at first was told this is what was available but after I questioned if a custom harness could be made he stated it would take around 10 weeks and a higher price which was fine with me. I sent the harness back on 12/04 and was surprised today 12/12 when the new harness was delivered. I now have a 599 BB and description describes it as (53 TD,DIP ON DASH,Late Pattern, Last few 100 cars.) This harness has a seperate extra extension for the dip switch and a seperate extra harness for the control box, so it is basically a late harness with extensions made up so it can be connected to my dash dip and move control box inside car. I called Josh and ask what happened to my custom harness and he said this was it,the company in England just happened to have it in stock and rushed it over. (Lucky me they brought one of the Concords out of retirement to rush my order).
I know this is long and winded but why would they put the dip back on the dash for the last 100 cars.

Irritated,
Rich
Rich (TD 3983) Taylor

Not sure what they sent you but this is what they claim a 599BB is:

MG TD # 29155-on
Braid wire, braid wrap, main wiring harness. Dip switch on the floor with turn signals and flasher relay on dash side of fire wall. (2 pieces)
Christopher Couper

Chris, here is a picture of the extensions that came with the harness and make it possible for a harness made to fit a TD with dip on the floor and turn signal control box and flasher in the engine compartment fit an early TD with dip on the dash and locate turn signal electronics on the inside of the firewall. I guess this is what makes it custom. On a plus side this may make the harness smaller where it goes through dash because the grommet went on fairly easy with room to spare. Notice my braid on braid wiring harness has one green plastic wire running through it; the green wire to the left of the green/yellow wire at the right of the picture.

Regards,
Rich


Rich (TD 3983) Taylor

This thread was discussed between 04/04/2010 and 14/12/2013

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.