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Banish your electrical problems!

PowerBlock wiring kit with color-coded wire bundles and the pre-wired power block
Advance Auto-Wire's “PowerBlock” wiring kit

Up until now, the MGB or Triumph owner has had only two options for improving the electrical systems in their cars: buy an OEM replacement or one of the many aftermarket wiring systems designed for street rods or custom cars. An OEM replacement only solves some of your problems, but doesn't solve any of the original design deficencies. You're still stuck with poor lighting, slow wipers, and sluggish heater fans caused by voltage drops through the old, worn out switches. The aftermarked kits available up until now are excellent, but they are not designed for an MGB or a Triumph, nor do they solve the problems with old switches. The majority of these kits are designed to mate with the GM steering column and the GM switches that are almost universally used in street rods, not for the switches we have.

The instructions supplied with these kits (usually pictorials) are quite clear if you are using these GM style components, but if not, you will have a heck of a time trying to figure out how to mate one of these kits to your car. Typical of the instructions supplied with these kits is this excerpt: “if you are not using a GM switch, you will have to trace out your wiring to determine how to wire the switch.” Huh? How much help is that?

None of them have enough relays to take the load off your OEM switches. Without the relays, corroded contacts in the switches will still have voltage drops that will leave you with dim lights and may even cause the switches to heat up enough to cause a fire. Replacing these switches is expensive and time consuming, and without reducing the loads, the switches will deteriate rapidly, setting you right back where you were.

Well, help is here! Advance Auto Wire offers our own “PowerBlock” wiring kit, made specifically for MGs, Triumphs, and other British cars, with wiring color coded to match the original Lucas color codes. See our “PowerBlock” system and our other products.

Complete PowerBlock wiring harness kit

Wiring harness

$790 postage paid

With seven relays, two flashers, eight fuses, all the connecters, terminals, and wiring needed to completely replace ALL the wiring in your car, this wiring setup will put an end once and for all to your British Car electrical problems! And not the wimpy wiring originally found in British cars - our wiring is all heavy gauge, top quality wire, made to handle the environment as well as the electrical loads. Heavier wire, combined with proper fusing, provides a definite improvement over the stock wiring! Electrical reliability in a British car!

Order Instruction manuals by vehicle

Why seven relays? OEM replacement switches for MGs and Triumphs are expensive and they are rather difficult to replace. By taking the electrical load off the switches and transferring it to the relays, the life of the switches is greatly increased. With relays, the switches only have to switch the very small load of the relay coils, letting the relay contact do the heavy current switching. In time, though, even the relays will fail and require replacement. Unlike the switches, relays cost around $5 or so, and takes all of 30 seconds to replace.

Perhaps the switches in your car have already aged to the point that the lights are dim as a result of contact degradation. Relays will operate with as little as 6-8 volts, so even your already bad switches will still operate them. Not having to replace your switches can save a lot of money.

Our power block wiring kits do not have relays for all functions, as some loads (such as the windshield wipers) are small enough not to need the benefits of relays. We supply relays for the following loads:

  • High beams
  • Low beams
  • Horn
  • Cooling fan
  • Ignition
  • Starter or Overdrive (depending on application)
  • Fuel pump

Why eight fuses? Because eight are enough. Unless you are adding extra, high current draw loads, eight fuses adequately protect your wiring. The 12, 18, or 21 fuse panels offered to the “street Rod” folks have fuses that you don't need in an MGB or a Triumph TR. If you wish to add extra, hight powered loads, you'll want to consider one of our auxiliary add-on systems - either the extra four-fuse auxilary fuse block, or the driving/fog light add-on relay/fuse block.

The diagram below shows the heart of our system, what we refer to as the “Power Block.” They come in two flavors, the one shown below with a starter relay, and one with an overdriver relay for earlier model Triumphs with an “A” type overdrive. In addition to a complete, pre-wired power block, each kit comes with the additional wire need to do the remainder of the car, interfacing with the power block. Also included with each kit is a complet set of terminals, connectors, mounting screws, etc.

Power Block wiring diagram with starter relay
The Power Block (starter-relay version). Select to enlarge.
Headlight relay kit with two relays and prewired leads

Headlight relay kit

$115 postage paid

Want to upgrade to a set of high powered headlights, but don't want to upgrade the rest ofyour wiring? Then this is the kit you need. (please note: our “power block” wiring harness kit is designed to handle headlights up to 110 watts each, so this kit isn't needed with our harness kit). This kit is designed to stand alone, so you may purchase and use this kit to add high powered lights to any car, whether or not you also have our power block harness system installed. The kit includes two relays, one for the high beams and one for the low beams, and four lengths of heavy gauge wire, all prewired and assembled. Each filament is wired and fused individually from the relays so there is no splicing or “daisy-chaining” required.

Order Instruction manual (PDF)

Headlight relay kit wiring diagram
Headlight relay kit wiring diagram. Select to enlarge.
Auxiliary fuse panel with four fuses and one relay

Auxiliary fuse panel

$90 postage paid

If you don't feel the need for our full wiring harness, or, if you're adding extra loads, maybe you could use one of these. Each unit has four fuses and one relay. Two of the fuses are hot all the time (for such things as power door locks, solenoid operated trunk release, etc) and two fuses that are switched by the relay. This relay can be wired to operate when the key is on (for such things as a power amplifier, power windows, etc.), or it can be wired to operate from a switch to control whatever you may wish to add to your car)

Order Instruction manual (PDF)

Auxiliary fuse panel wiring diagram
Auxiliary fuse panel wiring diagram. Select to enlarge.
Driving lights and auxiliary fuse kit

Driving lights & auxiliary fuse kit

$115.00 postage paid

Want to add a set driving lights and a few extra electrical loads? This is the kit you need. This kit is designed to stand alone, so you may purchase and use this kit to add driving lights and extra circuits to any car, whether or not you also have our power block harness system installed. In addition to relay switched driving lights, this kit also adds four extra fused circuits - two hot all the time, individually fused, and two switched on by a relay when the key is switched on, fed by a common fuse.

Order Instruction manual (PDF)

Driving lights and auxiliary fuse kit wiring diagram
Driving lights & auxiliary fuse kit wiring diagram. Select to enlarge.

Instruction manuals

To help you decide if one of our products is for you, please download the appropriate manual for the product of your choice. These are the same manuals that ship with the products.

These manuals are posted here in Adobe PDF format. You will need to have the Adobe reader to view them. If you don't have the reader, you may download a free copy direct from Adobe by clicking on the button below.

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Cover of an Advance Auto-Wire instruction manual

Complete wiring harness/power block systems

(for your convenience, right-click and select “save target as” to download to your computer)

Other products

Schematic diagrams

Perhaps none of our products are what you need. Maybe you want to keep your Little British Car stock, and just want to repair what you have. In that case, you might want a wiring diagram for your car that you can actually read! To help you, we have redrawn as many of the wiring digrams as we could find. To make them more readable, not only have we re-arranged them, we have also drawn them in color, with each wire printed in its correct color code. You can see a small portion of a diagram to the right to give you an idea of what these diagrams are like.

These diagrams are posted here in Adobe PDF format. You will need to have the Adobe reader to view them. If you don't have the reader, you may download a free copy direct from Adobe by clicking on the button below. The diagrams are printed on 11" X 17" paper to make them more legible, so if your color printer won't print on that size paper, you can take the PDF file to your local copy shop - Kinkos, Staples, etc, - and ask them to print them for you. This is a bit costly, so you may want to print only the pages for your car, rather than the whole set.

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Portion of a color-coded wiring diagram

Color coded wiring diagrams

(These diagrams were created using the best information available. Any given diagram may or may not specifically apply to any given model. Before using these, confirm that the diagram you are using actually fits the car you are using it with.)

For your convenience, right-click and select “save target as” to download to your computer

Other makes/model are in the works. Check back later for them.

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Technical assistance

If you have technical questions about our products, call us at 616-889-9707 after 1:00 PM Eastern.

Comprehensive tech support is available after the sale as well.

Contact information

For questions concerning the status of your order, or to enquire about future ordering, phone us at 616-889-9707 or e-mail us at sales@advanceautowire.com and we will respond promptly.

Customer comments

Here's what our some of our many satisfied customers have to say:

Well.... UPS just dropped off Dan's wiring harness and all I can say is WOW.

Top quality everything from the new power/fuse block to the wire itself. He also includes all grommets, bullet connectors, other modular connectors, heat shrink tubing, wire ties etc.etc. It's a bit overwhelming to look at all that wire that needs to be routed, cut, soldered and connected but it'll make a good Winter project now that retirement has taken place. I got lots of time now :-)

Bob D.

The wire loom arrived Friday as expected. To say the very least, I am impressed with the kit. I did not expect to receive all the wire and fittings to build a whole new loom. I was going to splice the new fuses and relays into the original loom that came with the car. However I now will spend several happy hours constructing a completely new loom with very high quality, heavy gauge materials and can forget the frustrations of sorting out the old stuff. Thanks many times over.

Stephen M.

...as you recall I recently ordered a wiring kit for a TR6. I also took your word and gutted the entire car as you requested. The day I did this my wife happened to be in the shop and saw the mess of old wiring all over the floor and her only statement was the project of restoring the TR has now come to a halt because I would never be able to accomplish this rewiring. All I said was TRUST ME and she laughed. My mind went back when I contacted you and you stated the same to me TRUST ME, well I did and I have been meaning to write to you for several days. In less than 2 weekends and a couple of nights after work I completed the job. I figure I have in app 36 to 40 hours in the wiring. I was really impressed not only with the kit but your instructions. I guess a jackleg mechanic can do it and with only 1 blown fuse while testing due to a switch getting grounded on the floor board which had not got mounted. My wife now is impressed (HA HA). Thanks again for your help and such a fine product.

Roger G.

Ordering information

To order a product by mail, please send a completed order form, along with a check or money order, to:

Advance Auto-wire
8277 Woodpark Dr
Byron Center, MI 49315

Or call 1-616-889-9707

Or, if you prefer, order online using the form below.

PowerBlock wiring harness $790.00

Vehicle

Please contact us for custom work or for cars that aren't listed here.

If this is for a triumph, do you have a type “A” overdrive?

Other products

Auxilary Fuse Panel $90.00

Headlight Relay Kit $115.00

Auxiliary Fuse & Driving Light Kit $115.00

Enter Additional Charges

(International shipping, extra parts, Supplies, etc.) Contact us at sales@advanceautowire.com for international shipping charges and product options.