Hi all - first post from me. I'm restoring a 1964 S3.8 auto, to a level to get it running and road-worthy again. Most work so far has been dropping the IRS to replace brakes and fix diff issues. However, this post is about electrics related to the 3.8 auto BW35, specifically if anyone knows the right part for the reverse light/engine cut out switch, or can read the below and tell me why my logic is wrong...

The problem - my reverse lights don't work, and never had since I bought the car 3 months ago. The wiring and bulbs are fine, I know the issue is with the combined reverse light and engine cut-off switch located behind the steering column, because if I bypass it, the reverse lights come on. This switch is a 4 pin switch controlled by a rotating arm connected to the gear selector lever, and on my car it's a Lucas 55SA (photo attached).


So I bought a replacement switch, but it doesn't work either. When I tested them both, they have identical characteristics, ie my original one works the same as the new one. But although it fits and looks the same as the one in the Service Manual, I can't see how it can be the right part. Reason is the way the switch works - see 2nd image which represents the rotary arm of the switch and whether the switch is open (off) or closed (on).


Therefore, both these Lucas 55SAs turn on the Reverse lights in both Park and Reverse, then off. And the Engine cut-off will disable the ignition in P, R, N and D2. So neither set of terminals does the right thing. A previous owner had connected the engine cut-off wires to terminals 2&4, instead of 1&3, which would work, but then the reserving lights would come on at the wrong times, which I guess is why they were disconnected when I bought the car.

So do I have the wrong part, or am I doing something else wrong? Has anyone out there faced this issue or knows an answer?
Many thanks,
Chris.

 

Chris, your car being a 1964 should have the DG250 Auto box and the switch you are trying to rewire is fitted to the DG250 behind the dash. On the BW35 the reverse and cut off switch is located in the side of the gearbox. There is a panel in the left side of the gearbox tunnel to access it or you might have to go from under the car if your car has had a swap as the panel might not be there.
If you do have a BW35 box maybe the previous owner has swapped gearboxes, left the original switch in place but tried to rewire it to work with the BW35 switch.
Can you clarify which gearbox you have in the car please?
I also posted this reply on the Jaguar SType forum for you.

 

Thanks for the reply Cass. Good question - I'd just assumed it was a BW35. Now I've checked info on the dates when DG250s were installed, you're probably right since my car is either late 1964 or 1965. I've looked underneath and I can't seen anything stamped on the GB itself, but though I'm no expert the shape of the gearbox sump and convertor housing bottom cover both look identical to the DG250, not the 35, when I compared to the parts images on SNG Barratt's site. The original GB number is JBC22358P. (though of course someone might have switched boxes sometime in the last 50 years.) So let's say I have the DG250 gearbox since the dates match and the shape of external parts look correct. However I've read that the P, R, N, D2, D1, L sequence comes with the BW35, and that's the sequence I have... but it explains why I'm being sent reverse light switches that would suit P N D L R if that's the norm for DG250.

So I'm still a bit confused but your question has helped me move forward, thank you. Any further thoughts greatly appreciated.

 

Chris on the gear box there is a riveted plate that is situated high up on the left side of the main body. At least that is where it is on the BW35. I have no experience with the DG250 box so all the descriptions here relate to the BW35.
On the BW35 there is an inspection plate on the left side of the gearbox tunnel under the carpet. If there is no panel under the carpet you can look under the car at the side of the gearbox. There should be the gear change cable and a thinner second cable going to the engine bay. The second cable is the kickdown cable and attaches to the back of the carbs. There should also be some electrical cables for the inhibitor and reverse lights switch which is screwed in to the side of the gearbox just above the pivot for the gear change. If I am not mistaken there should be no electrical wires going to this point on the DG250 as these are all up behind the dash.
On my car my gear change indicator is P R N D 2 1 on the dash. My car is a September 1967 built 3.4s Auto.
DG250 boxes had the prefix JBN or JBC and the BW35 began with FG.

I cannot post photos on this forum due to there megre limits but if you come up on the S Type Forum I will post photos of the side of my gearbox for you to compare with yours.
Rob.C.

 

Chris,
if you confirm the transmission is a DG250, instead of a BW35, then there is an error in the wiring connections of the Neutral Safety Switch in the factory electrical schematic that has never been corrected by Jaguar.

I had the similar problem and corrected it, for which I made a writeup explaining the error and the correct wiring AND adjustment of the switch's lever arm. Yes the switch itself has two adjustments, one clockwise / counterclockwise, and another adjustment FORWARD/BACKWARD.

But if your transmission is a later BW35, then the NSS is at the transmission itself, so you will need to eliminate the switch mounted at the steering column, and extend the wires to the switch at the transmission, which is not difficult to do. You will need a 5 feet long vinyl loom and 5 feet of wires each in the correct colors.

If you do have a DG250, (you can see the I.D. plate on the side of the transmission), then send me a PM and I will send you the writeup for the steering column switch.

 

Good to hear from you again Jose. Is there a chance you can either post that info on this topic or submit a link to where you have posted it before just in case someone else has the same problem and then they can read or access it from here. Rob.C.

 

Thanks Jose, sorry for the slow reply, I've been hiking for 10 days.
Yes, I have the DG250, so that write up of yours would be great. Since you said you prefer a PM, I'll drop you a contact request now.
Cheers,
Chris.

 

send me a PM with your email so I can send you pictures and a text file explaining the adjustments. I cannot attach files to private message replies. I assume you have the 4 wire connections sorted.

 

Hello all, apologies to 'jump in' on this thread, especially as a 'newbie' - I have the same problem with a DG250 on a 1958 Mark 1 auto - with the PNDLR slider just under the dash - Jose would you mind sharing those instructions of yours with me too ? It would be much appreciated. I am new to the forum and whilst I can rebuild Jaguars I cant seem to PM you ! I'll keep trying.

 

Hi veloce500.

Let's try this:

Go to my S type website below and download the S type factory Service Manual, and I also have the MK-1 manual if you don't have one. You can contact me from there too.

https://classicstypeparts.webstarts.com

 

Thanks Jose - email sent via your website as suggested
Regards
Andrew