The 'E' Type Forum

Took the E Type to lunch in the country and had no problems whatsoever on the outward journey. On the way home the ignition light flickered on and off and by the time I had covered 50 miles is was on permanently. However the ammeter was showing a small charge all the time even with the fans running in the London traffic. I checked the voltage in the battery when I arrived home and it was 13v. Duff voltage regulator?

Stuart

You need to make sure what it is which drives your ignition warning light . Some were relay driven from the charging system , but there was a period from about 1965 on ( end uncertain ) when the "ignition" light was actually operated by an oil pressure switch plugged into the right hand gallery just ahead of the oil filter housing

To be clear, the voltage regulator (VR) on the E-Type controls the operating voltage going to the minor gauges. The battery voltage is maintained by the 4TR Control Box. Neither of these is likely to be the reason your ignition light is coming on given the battery is showing 13v at the end of your trip. Chief suspect will be the 3AW ignition warning light control unit if you car is fitted with one. As Christopher says, Jaguar fitted an oil pressure switch to the side of the block for the first 3 years of 4.2 production which illuminated the "ignition" warning light when there was no oil pressure i.e. the engine was not running but the ignition switched on. They then moved over to the 3AW control unit which operates as one would expect, via the alternator. The date of the change was September 1967 from cars 1E1724/21481/13151/33091 which should give an idea in which direction to look.

The 3AW control units are known to be failure prone.

David, may I query your date of Sept 67? Mine is 1E21509, date of manufacture 25th April 67. It does indeed have the 3AW rather than the oil pressure set up.

The date is that of the Spare Parts Bulletin which was probably behind the actual production, hence I quoted the car numbers. I will add a copy of the relevant SPC tomorrow but we always go by the car number rather than the date of the SPC.

Thank you everyone.....I will get a new 3AW units as it does appear to be the original part. Just for the record my chassis number is well beyond the 1E21481 cut-off.

Stuart

Jumping on the back of Stuart’s post.

I recently replaced the original 3AW unit with a new electronic version as forum posts suggested the originals were prone to failure.

I now have ignition light ‘flicker’ which I never had with the original unit. I don’t think I have a charging issue.

Any ideas anyone?

Cheer’s
Ash

Ash,

The voltage that drives the 3AW has "flicker on it", so depending on how the electronics have been designed in the replacement unit it's possible for that flicker to get through to the ignition warning light, especially at low RPM. The original 3AW's used a thermal mechanism so the thermal lag eliminated any flicker.

The 3AW unit has no influence on charging or the voltage regulator, it simply senses the alternator is generating power and turns the ignition warning light off.