Bad day on the LUCAS 3AW Warning Light Control Unit production line?

I am sorting out why the red “Ignition Warning Light” in the speedometer of my 1969 E-Type FHC no longer works and I found lots of helpful trouble shooting advice in the Jag-Lovers archives from those that have had this problem and resolved it. So thank you to all of those who have made the effort to post about this. :smile:
When I tested the 3AW Warning Light Control Unit (Lucas part number 38706A, Jaguar part number C24169) in its place beneath the heater box, it failed the recommended resistance test. I removed it from the car, removed the metal casing and found that some of the small internal wires were broken. What I also found interesting was although the metal casing had the correct Lucas part number and a date stamp of 26 69, the round fiberboard bottom of the 3AW didn’t have the “E”, “AL” or “WL” marking stamped in it as I have seen on other 3AWs. When I removed the metal casing I could easily see that the round fiberboard bottom was installed backwards with the terminal markings located on the inside where they couldn’t be read and where they were now the mirror image of where they should be with “E” and “WL” reversed. It must have been a bad day for someone on the LUCAS 3AW production line the day that my 3AW was made. :smirk:





From my testing so far it appears that I might have a bad alternator (diode failure?) as well as a failed 3AW, but that will be a future post once I resolve the issue and get my Ignition Warning Light working again. The bulb tested good when removed, but I couldn’t get it to light up with the ignition on and the Brown-Black wire grounded. So I might also have a broken wire or two or a bad bulb socket. So more for me to sort out.

Paul

My 3AW quit working on my 67 E-Type and I replaced it with one from CoolCat Express about five years ago. Left the original in place (sans wires) and secured the new one behind it. Looks good and has been working great ever since.

https://www.coolcatcorp.com/Merchant5/merchant.mvc?Screen=PROD&Store_Code=CEC&Product_Code=SS3AW&Category_Code=EL

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Drew,
Thank you for the tip. I read about the CoolCat unit in some of the archived posts. I need to sort out if my alternator is bad first before I install another 3AW of any flavor to avoid burning that out. I will consider the CoolCat unit among my 3AW options

Paul

The alternator can burn out the 3AW…but not without help. The usual cause is a loose connection somewhere, which can cause a load dump as the stator de-energizes. Check your main B+ cable, your battery cables, and your grounding strap. Then check the alternator function. If everything is ok, then you can try a new 3AW.

How did you get the relay open to look at the innards?

CU_Man,
I used a pair of pliers and carefully bent back the edges of the metal casing of the 3AW at the base where it met the round fiberboard. It only took a minute of so. Once I bent enough of the metal casing back all around the fiberboard I was able to carefully pull it apart and inspect the components inside the metal casing.

Paul

Michael,
Thanks for your help. My 3AW had obviously failed and I have ordered a replacement that I expect to arrive in a couple of days.
I found an intermittent problem with the bulb and holder for the ignition warning light and fixed that by cleaning the contacts in the bulb holder and installing a different 2.2W bulb that had a slightly longer base. That light now illuminates properly with the ignition on and the NB wire from the 3AW WL terminal grounded. Today I tested the alternator output on the NY wire to the 3AW AL terminal and ground and found it to be too high at 8.5V AC so I adjusted the potentiometer on the rear of the 4.T.R. down and it is now within the 7-7.5 VAC spec range at 1,500 engine RPMs. A very minor adjustment counterclockwise was needed.
I hope to have a properly functioning Ignition Warning Light again this week and will post once I install the new 3AW and test it out.

Paul

Success! I received the New Old Stock (NOS) 3AW that I purchased on eBay yesterday, installed it today, and for the first time in years the red “Ignition” warning light in the speedometer of my 1969 E-Type FHC is working properly again. :blush:My thanks to those who have posted about problems with the “Ignition” warning light before. The archives are a veritable gold mine of good info about how to troubleshoot and fix issues in these cars.:grin:

The pictures show the old and new 3AWs, and the “Ignition” warning light on with the engine off and off with the engine running.:blush:




As a summary, the problem was due a failed Lucas 3AW, an intermittent bulb and holder, and an out of adjustment 4.T.R.
My next project is to return my original windscreen washer to full operation again. I am certain that will be somewhat challenging as well although the electric washer motor works, so l have that going for me. :slightly_smiling_face:

Paul

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I don’t believe it was just a bad day at the factory. I came across an old 11-66 3AW in my used parts storage and, like you, I had opened the can.

The terminal markings are on the inside of the base.

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Could be that particular “line worker” had dyslexia. Five out of 3 of us have it!!! :crazy_face: :crazy_face: :crazy_face:

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Ah leave it alone for awhile and enjoy the feeling you don’t want to drive in the rain anyway. I bet your happy :smiley: see you can do it
Cheers

Generally – there are two types of people: those who can count and those who can’t.

Jim,
Well, the truth is this is part of my penance for letting my E-Type sit for more than a few years while I worked on and restored my other 5 Jaguars. My E-Type was my daily driver for several years and it received lot of love and attention from me during that time. But then the engine oil pressure was getting very low, and the clutch started to slip, so it sat while I tried to sort out what to do. I had the engine rebuilt and the clutch removed and replaced in 2021 (and I also sold three of my Jaguars) before moving from California to South Carolina.
Since getting my E-Type back on the road again, I am doing my penance. I removed and replaced the tires, front shocks, front brake hoses, all of the coolant hoses, the front anti-roll bar bushings, battery, windshield wiper blades and more. I also fixed the ignition warning light, installed a right side exterior door mirror and fixed several other minor issues. I am driving the car regularly again and making up for lost time. I just re-torqued the cylinder head nuts a few days ago since I have put on just over 500 miles since the engine and cylinder head were rebuilt.
After a thorough cleaning the windshield washer reservoir appears to be in good shape and the motor seems to be functional. I will repaint and remount the bracket this week after the new reservoir retaining strap arrives along with some other parts from Moss Motors. I hope to get the windshield washer working before the end of April. Lots to do, but all of it good so far. :grinning:

Paul

Sounds like you have it under control ,I find I have to be in the right mood for some of these jobs a break helps me get in the zone

Cheers

When I bought my car the whole bottle/washer motor was missing but tubing was sticking out of the firewall, thank goodness. Hardest part for me was priming the system all the way up to the sprayer nozzles. I had no need to use the washers for a year or so and they lost their prime. Now I operate them every few weeks at least and all has been good.

David
68 E-type FHC

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Craig:

3 tails… All I could handle at once!!!