Using a Mark II wiring harness on a Mark IA

[fjohn49]

I want to replace the wiring harness on my Mark IA. The generator was previously replaced with an alternator and additional wiring was added to the harness. In reviewing the wiring diagrams for Mark I and Mark II cars, they are identical with the exception of the generator and alternator wiring. The Mark II has an 6RA relay and resistor for the ignition warning light. (Also back up lights, switch, etc.) I've looked at the British Wiring Mark IA wiring harness with the added alternator wiring. British Wirings design is basically for a Lucas alternator with the battery connection, a sensing connection and an excitor connection that also operates the ignition warning light. The wiring for the generator voltage regulator and ammeter are removed.

I have not been able to locate an alternator that has the three connections in the British Wiring harness that fits that appears to be able to mount on the tiger without major bracket modification. I can find single wire alternators that will mount, but they do not operate the ignition warning light.

Has anyone used single wire alternator and rewired for the ignition warning light to work or replaced a Mark IA harness with a Mark II? I've heard some of the connectors are different on the Mark II harness.

Thank you,
John

 

[Austin Healer]

The connectors for the main to body wiring harness and plug type, not "snap" connectors like the MK1a. Additionally the turn signal switch and the hi beam switch are also plugs.

You can use the Ford alternator, 6RA relay and resistor for the MK2.. the alternators are widely available, as are the 6RA relays.. the problem is coming up with the resistor which is rated at 15ohms/5 watt . These were only used on the Mk2 Tiger and some Jensen Interceptors. I can rebuild an "open" resistor or convert a Lucas ballast (1.6 ohms). The Lucas ballast resisters look exactly the same as the 15ohm unit used in the Tigers. To convert a ballast I would need an original old stock unit from the 60's or 70's.

you can use a one wire alternator with either the Mk1a or MK2 harness, you just won't have the functional charge lamp. A simple work around would be to install either an amp gauge, or volt gauge. The Mk2 harness doesn't support an amp gauge. You have to make that addition to the harness yourself.

The original cast iron Mk2 alternator brackets are VERY hard to find. There is a cast alloy repro that is a functional replacement, or you can use the one fabricated by Robert Straghan (Hoghead on the forum) I believe that this uses a Denso alternator

 

[Theorangetiger]

I converted my MKI to an alternator and installed a stock MKI harness from SS, making the adjustments for the alternator, new regulator and ignition warning light. I also switched from an ammeter to a volt meter which is super easy. Everything went smoothly and I would recommend this route.

 

[fjohn49]

I converted my MKI to an alternator and installed a stock MKI harness from SS, making the adjustments for the alternator, new regulator and ignition warning light. I also switched from am ammeter to a volt meter which is super easy. Everything went smoothly and I would recommend this route.

Thanks for the reply. I've thought of doing it this way since the original Mark 1A harness had been adjusted for the alternator set up.

 

[fjohn49]

The connectors for the main to body wiring harness and plug type, not "snap" connectors like the MK1a. Additionally the turn signal switch and the hi beam switch are also plugs.

You can use the Ford alternator, 6RA relay and resistor for the MK2.. the alternators are widely available, as are the 6RA relays.. the problem is coming up with the resistor which is rated at 15ohms/5 watt . These were only used on the Mk2 Tiger and some Jensen Interceptors. I can rebuild an "open" resistor or convert a Lucas ballast (1.6 ohms). The Lucas ballast resisters look exactly the same as the 15ohm unit used in the Tigers. To convert a ballast I would need an original old stock unit from the 60's or 70's.

you can use a one wire alternator with either the Mk1a or MK2 harness, you just won't have the functional charge lamp. A simple work around would be to install either an amp gauge, or volt gauge. The Mk2 harness doesn't support an amp gauge. You have to make that addition to the harness yourself.

The original cast iron Mk2 alternator brackets are VERY hard to find. There is a cast alloy repro that is a functional replacement, or you can use the one fabricated by Robert Straghan (Hoghead on the forum) I believe that this uses a Denso alternator

Thanks for the reply, I haven't decided which route to go yet. Changing the connectors for the dimmer switch and turn signal switch wouldn't be a problem. I can also get a 15-ohm 5-watt resistor to set up for the charge light. The car I have now was set up with an alternator and I'll have to check to see if a resistor was added for the charge light. (The car is totally disassembled and in the body shop.) Whether I go with a Mark 1A harness or a Mark II, there will be some adaptions necessary to make it work. I had planned on adding a voltmeter which ever harness I use. Bill Martin is currently looking for a new source to make the aluminum reproductions of the Mark II alternator bracket. I do have another bracket that will work for the Ford alternator, but it needs adjustment for the correct pulley alignment. The third option of a 1 wire alternator and voltmeter is very appealing.

Thanks again

 

[Austin Healer]

Thanks for the reply, I haven't decided which route to go yet. Changing the connectors for the dimmer switch and turn signal switch wouldn't be a problem. I can also get a 15-ohm 5-watt resistor to set up for the charge light. The car I have now was set up with an alternator and I'll have to check to see if a resistor was added for the charge light. (The car is totally disassembled and in the body shop.) Whether I go with a Mark 1A harness or a Mark II, there will be some adaptions necessary to make it work. I had planned on adding a voltmeter which ever harness I use. Bill Martin is currently looking for a new source to make the aluminum reproductions of the Mark II alternator bracket. I do have another bracket that will work for the Ford alternator, but it needs adjustment for the correct pulley alignment. The third option of a 1 wire alternator and voltmeter is very appealing.

Thanks again

Here's what the Mk2 looks like. There's a bracket on the LH top hat for the resistor and relay. The regulator is mounted right behind and directly to the side panel

 

[boss-tiger]

Since alternator is not original (assuming your not worried about stock), I really like the Rebel wiring kit that I just put in my car, has more fused circuit's, assume more same overall and combined that with a single wire alternator that mounts same as old Ford alternator - works great and very easy installation. If you want more 'original' look you would want to wrap the wiring in engine compartment. I did use a Mk2 repo harness in a Mk2 from SS and it worked/still working great also.

 

[Austin Healer]

Rick's source for the harnesses is British Wiring... their source is Autosparks in the UK... If they do not hold patterns for your particular application, they can make harnesses from your patterns or drawings. I had them make a harness for my father's Sunbeam Talbot Mk2a DHC, and another for an Austin Healey MK2, 2 seater that they didn't have a pattern for. Both came out spot on, and were much more economical than Rhode Island Wiring... they (Autosparks) also were able to make up a harness for a '66 Triumph T100 (Tiger) trials bike I restored. It was a "one of six" bike, so no harness was ordinarily available.

Autosparks and British Wiring also have the correct woven ground strap and battery ground cables, the correct heavy gauge positive battery wire and the correct battery terminals. I get the cable ends from Holden, also in the UK. They (Holden) also have the plug ends for the Mk2 wiring harnesses. for the turn signal switch, main to body harness and hi beam switch.

They (Autosparks) were also able to supply a correct air con harness for factory air on the Aston Martin DB5 I am currently restoring.

Autosparks is the original supplier for wiring harnesses in Brit cars and bikes... Lucas did not make up the harnesses.

 

[Austin Healer]

Mounting a one wire alternator is dead simple... Just run the wire from the alternator directly to the solenoid. (battery side) The side with the brown harness wires connected to it! A voltmeter can be connected to ANY source of positive voltage... But I'd use any wire in the white wire circuit as these wires are only "hot" with the key on. You could also use any wire in the "green" circuit, like the feed to the voltage stabilizer. This circuit is only hot with the key "on", but is fused.

if you wire the voltmeter to the "brown" circuit it will read all the time and be a small drain on the battery.

 

[theo_s]

Generally speaking, a voltmeter is a much safer instrument than an ammeter, and for an alternator equipped car it's more relevant as an indication of what's going on.

An ammeter needs to be wired in series between all the loads and the battery, and it needs to be able to support the maximum current you might be pushing to the battery (or that the battery might deliver to the car, with the exception of the starter). If you've upgraded the electrical system with an alternator that can push 70 amps or more, and you've added extra loads such as a big stereo, better lighting, or power windows, door locks or AC, then you need to up-size the wiring going to and from the ammeter accordingly, or else you'll create local hot spots in the harness. Typically that can occur at the ammeter connection itself, and it can get hot enough there to melt the plastic parts of the connectors and/or the instrument.
A voltmeter, on the other hand, wires in parallel with the other circuits on that node (white or green circuits as Sean notes) and draws a relatively small current, so it is not a liability to the rest of your car.

 

[fjohn49]

I'm leaning toward using the 1A wiring harness and a 1 wire alternator. There's an option for the charge indicator light from American Autowire. They have a module to connect the charge light to operate whenever the voltage drops below 11 volts. It's $40.00 and the wiring is simple, powered by the ignition switch and the charge light is connected directly to 2 wires on the module.
https://americanautowire.com/produc...os=1&_psq=charging+warning+light&_ss=e&_v=1.0. This may be more economical than purchasing a volt meter to install in the clock opening on the dash. I do have a set of the optional back up lights that I intend to install with the switch installed on the shift linkage as the Mark 2 had. Tis wiring will be simple to add as I run the new harness.

 

[fjohn49]

Rick's source for the harnesses is British Wiring... their source is Autosparks in the UK... If they do not hold patterns for your particular application, they can make harnesses from your patterns or drawings. I had them make a harness for my father's Sunbeam Talbot Mk2a DHC, and another for an Austin Healey MK2, 2 seater that they didn't have a pattern for. Both came out spot on, and were much more economical than Rhode Island Wiring... they (Autosparks) also were able to make up a harness for a '66 Triumph T100 (Tiger) trials bike I restored. It was a "one of six" bike, so no harness was ordinarily available.

Autosparks and British Wiring also have the correct woven ground strap and battery ground cables, the correct heavy gauge positive battery wire and the correct battery terminals. I get the cable ends from Holden, also in the UK. They (Holden) also have the plug ends for the Mk2 wiring harnesses. for the turn signal switch, main to body harness and hi beam switch.

They (Autosparks) were also able to supply a correct air con harness for factory air on the Aston Martin DB5 I am currently restoring.

Autosparks is the original supplier for wiring harnesses in Brit cars and bikes... Lucas did not make up the harnesses.

The wiring that Rick (now Patrick) stocks, appears to be the stock Mark 1 -1A harness as is Classic Sunbeam. Autosparks and British wiring have multiple options that can be added to the harness, such as alternator, radio, electric fan, etc. The standard 1A harness would suffice using a 1 wire alternator. The cable from the alternator to the starter solenoid can be easily sized and purchased with the correct terminals locally, for the 1 wire alternator.

I appreciate all the feedback