The topic of sequential start systems on late Series III E Types came up in another thread regarding sensor identification, but since the subject probably escaped the attention of most I am posting it separately. I am just beginning my study of the E Type electrical system, complicated by the fact that my knowledge of electrical systems in general could be fairly described as sketchy.
In the attached photo you can see that the large white(ish) multi-connection plug in the center of the panel section is unplugged from the sequential start logic controller (gray box). It has apparently been that way since before I bought the car in 1985.
I presume this was done to disable the safety checks (seat belts, etc.?) that prevent starting the car. My question is whether disconnecting the plug impacts any aspect of vehicle operation other than disabling the pre-start safety checks?
And while I am asking dumb or lazy questions, what is the round silver device that looks like a cigar lighter that is mounted on the bracket on the fold-out instrument panel directly above the fuse chart?
Thank you, and I will study more before asking more wiring questions.
I’ve never seen your first mentioned item on an S3 car and the second item is definitely an add on. It looks a lot like a Cigarette Lighter module and may have been added to provide a 12V outlet in addition to the provided Cigarette Lighter.
Thanks, Bill. We have established that the sequential start system (gray box and plug) was OEM standard at least on U.S. cars for 1974 (and maybe earlier), no doubt due to our overzealous government regulators who decided that they should force people to wear seatbelts and not let people engage the starter except when it is in park (it is an automatic transmission car)… The other device may be related to some U.S. specific issue, it does not look to be an amateur installation and it would not make sense to have another outlet that you had to drop the instrument panel to access. But with the prior owner I suppose anything is possible.
Assuming that lighter looking thing is an add-on, it may have been the power supply for the car alarm that had been removed prior to my purchase in 1985. Your comment just made me think of that possibility.
I have not found that the principle of Occam’s razor applies to Jaguars, but the simplest explanation for
a mysterious device that looks like a cigarette lighter is that it actually is one.
Sorry, the other part of the information did not attach.
If you have a copy of the RTC9014 Parts Catalogue your answer is found on pages 27.72 or 27.73. It’s part of the Sequential Start (Interrupt) system… Does your car have this logic control unit (located behind folddown instrument panel)?
As you have ascertained, the component attached to the back of the Temperature gauge appears to be a cigar lighter accessory. Most likely it was installed to plug in some sort of alarm system??? Very strange indeed. That’s why I’m a purist. Trying to decipher what the PO(s) did (no documentation) is a true nightmare!!! While the car may have shortcomings it was, for the most part, well engineered. Apart from Lucas, most problems arise from a lack of maintenance or a lack of understanding!
Great photo. Says a lot! Keep 'em coming.
Since you have several S3 E-types (1974 MY) cars in for work could you possibly take photos of the inside of each instrument panel area? That would be most helpful. Car Chassis Numbers would be of great benefit also!
Second request: Are the four cars LHD , RHD or a mix?. If LHD were they imported from the United States?
Jaguar produced cars subject to the destination market (regulations). It would be most informative to the group to know the background of the four cars and photos detailing how they came equipped.
Thanks for your input and look forward to your updating post.
if you look under the centre dash, you’ll find four white/yellow wires linked to each other by bullet connectors. One comes from the ignition column, one goes to the starter relay and two go to the seatbelt warning system (“SBW”) box with the round plug.
It’ll be currently wired so the seatbelt warning system is sitting in between the ignition switch and the starter relay.
If you swap those white/yellow wires over with each other, the silly box will be just connect to itself, i.e. be “out of the circuit” and the ignition switch will run straight to the starter relay just like it does with all the other cars. You can then simply unplug the round plug, as the box can no longer interrupt the feed to the starter relay depending on its seatbelt and seat inputs.
The wiring diagram for your car is in the tan coloured (A5 sized) Owners Manual.
This is what is inside the SBW box. I posted this in 2012 on the old site photo albums…
I think I may have solved the mystery. A search for US safety regulations showed that effective in 1974 there was a new US safety regulation that required a safety interlock system on all vehicles that prohibited starting unless seat belts were fastened. Because this was such an inconvenience, that law was very quickly repealed. So the vehicles with the Sequential Start System we probably those manufactured after January 1, 1974.
"1974: First Airbags
In 1974, General Motors produced the first airbags, opening the door to the more advanced technologies we take for granted today. Also in 1974, the U.S. enacted a federal rule requiring all cars to have seat belt interlock devices that kept the car from starting unless the driver (and, if present, front passenger) had their seat belts engaged. Public outcry over the inconvenience of the measure saw the requirement repealed almost immediately. In the wake of the seat belt interlock fiasco, it wasn’t until 1984 that New York state introduced the first law requiring the use of seat belts (by 1995, 49 of the 50 states had seat belt laws)."
It looks like that VIN Bill shared is a very early 1974 model, since the first 1974 Jaguar Heritage lists is 1S24476. Mine that has the sequential start is a late one, UE1S25268BW.
It appears that Jaguar made their interlock system (Sequential Start System) so that it could be easily disabled by just unplugging that white connector that started this conversation, and probably just about everybody did it. The bad part for me is that this short-term misguided regulation is now going to haunt me almost 50 years later in putting the car back together.
Correction, see below from a New York Times article. In light of this it is not clear how Bill’s December 1973 build of a 1974 U.S. Series III avoided it, unless a prior owner had it removed.
“The seat belt interlock, required by the Government on cars sold after Aug. 15, 1973, requires motorists to fasten their belts before a vehicle can be started. Many owners disconnected the system in protest.”
Coming to this party a little late - sorry.
I have half a dozen photos of “various” dash interiors featuring this wiring. I’m posting all of them here in hopes a gem appears in one of them that breaks the code on something. As I look at them more closely, they ~may~ all be from the same Primrose Series III?? Some clues may be available in the captions as well