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Hi all, I'm looking to get some advice on the innition warning light circuit on my Jan 1967 S1 2+2.

When I replaced the wiring harness during the rebuild, I was working on the alternator circuit wiring and noticed there was no provision in the harness to connect in a 6RA relay. The harness supplier told me that the series 1 2+2 was different and there was no 6RA relay on this model, just the 3AW relay for the ignition warning light. At that time I fitted a solid state replacement instead of the original 3AW unit and forgot about the 6RA

The car has been running fine for the last 1500 miles of running in, until a couple of weeks ago when my ignition light stopped working. Apart from this, everything else seems to be ok, The car is working normally and I have driven home 25 miles in the dark with it after a local region meeting. I also did a 110 mile round trip to Donnington with no problem.
I have cleaned and checked correctness of all the connections but to no avail. If I ground the warning light bulb direct to earth and switch on the ignition, the bulb lights up but will not go out when the engine is started, though I have only left this connected for a few seconds in case it caused any other problrms.

When I put a multi type volt meter across the battery terminals and start the engine, the battery voltage begins to rise from 12.75 volts to 14.5, so the alternator is charging. The ammeter kicks into full charge indication on start up, then falls back close to zero after some seconds, which I think indicates that both the alternator and the 4TR are working.

My main question is. Should I have a 6RA relay in my circuit?
Are the any members with similar age S1 2+2 cars that can look at theirs and confirm if one is present.
Has anyone any advice about troubleshooting the non working ignition light??
Any help and advice greatly appreciated.

Thanks.
Art

Hi Art,
I may be able to help just a little.

Back in the sixties I fitted a 4.2 engine from a very badly bent almost new 420G (Mk10) into a Mk 7. This entailed going from a generator with voltage control box to an Alternator with 4TR voltage control box.

I do believe that many electrics were common across the range hence my peneth.

During that period the 4TR controller (voltage regulator) was bulk head mounted with later Alternators having the voltage regulator incorporated inside the Alternator casing. Pity really as I have had to remove the Alternator twice in 40 years to replace the voltage control bit.

The Battery and Alternator appear to be OK as you have described.

Now we come onto the ignition warning light. If you know how the Ignition warning light works on the old style voltage control box - well it is nothing like that at all - I'll come back to that if there is a need. The description - ignition warning is a misnomer any way cos it is nothing to do with ignition. It should be generator/alternator failure warning light.

Getting back on track. I vaguely remember agonising over a connection for the warning light only to find that an oil pressure switch in the oil gallery of the block is used to switch the said ignition warning light on/ off.

Do you have a wiring diagram for your vehicle?

Looking at my Mk10 workshop manual (proper Jag Manual) wiring diagram the supply for the ignition warning light bulb comes off the live side of the Hand brake warning bulb. I also found the 3AW relay to which you refer but need to study the wiring diagram further to understand it's purpose. It's getting a bit past my bedtime so that will have to do for now

I hope this helps a little - do tell us how you get on

Oldtimer

My 66 2+2 only has the 3aw relay

Chris

Thanks Oldtimer and Chris!

Chris your post confirms what I was told, and I have subsequently seen an article on the 1.5 series E type which confirms that the 6RA relay was introduced when the steering locks were fitted on these cars.
Now back to the 3AW issue. The best test with the solid state 3AW that I had fitted is by substitution, so I ordered one. Whilst I was waiting for this to arrive, I decided to pull apart the old Lucas 3AW and have a look inside. Basically it is a thermal switch which functions in a similar way to the bi-metal switch in a flasher unit. I noticed however that the contacts on my 3AW were jammed shut, the contact post had probably warped over the years. I tweaked this to allow about 0.5 to 1 mm of movement and then checked the resistance readings between the contacts with an Ohm Meter. (These are given in the service manual). The readings were all ok, so I cleaned all the external/internal contacts, reassembled it connected it into circuit.
Hey Presto, it works!!!! I now have a working warning light again, which goes off as soon as the alternator starts spinning. I guess for the time being I'll leave the original one in circuit and keep the new solid state one as a spare.
By the way, The solid state one had obviously failed after just one year. Not what I would have expected for the price paid
Art.