I am trying to hook up a Dynamator upgrade alternator (looks just like a C45 Lucas generator) to my 1956 XK140 OTS. The instructions say that an all-critical module needs to be spliced into the wire between the ignition switch and ignition light.
On my wiring diagram however , the ignition light shows 2 wires to the ignition light; #9 white and #25 yellow. However, my ignition light works with only one wire which appears to be white, and the bulb, grounds to the metal plate behind the panel. (My turn signal works the same way.)
My Jag is positive earth and has cloth insulated wires that were replaced in the 1990’s and which have always matched to the wiring diagram’s color coding in the past.
Q: CAN ANYONE EXPLAIN WHY THE WIRING DIAGRAM SHOWS 2 WIRES WHEREAS IN REALITY THERE IS ONLY 1?
Your ignition light should not run to ground. If it does, it just tells you your key is on.
It is supposed to go off when the car starts, and come on to tell you when your generator is not charging.
Seems to me that your #25 yellow is missing, it ought to run to terminal D on your voltage regulator.
Further to what Rob has said, the way the ignition lamp should be wired is one wire (white) via the starter push button and ignition switch goes to the battery negative and the other (yellow) goes to the D terminal on the RB310 control box which in turn is connected to the dynamo D. When you turn the ignition on the lamp illuminates because at that time the D is effectively grounded via commutator in the dynamo. Once the dynamo is running and generating an output the voltage on the D terminal rises and eventually the lamp has almost the same voltage on both sides so it goes out indicating the generator is working.
I couldn’t find much information about the Dynamator wiring but there is more about something similar called Dynalite. This has a specific terminal for the warning light but when used on a positive ground vehicle it needs a relay in the ignition light circuit. This may be the module that you mention. If you able to scan the wiring diagram that came with the Dynamator we might be able to help a bit more but like Rob, I can’t understand how your existing ignition light would work correctly if one side of the lamp is grounded.
EricRob, Thanks for your responses. Attached is a picture of my ignition light; it worked fine with the dynamo. As you can see, it’s single wire that appears white(#9?) and it has a clamp socket that grounds and completes the circuit. I’m still baffled by the 2-wire depiction on the wiring diagram below?
The #25 yellow wire to the “D” terminal d in the background, but I can’t figure out where it connects behind the dash.
John
1956 XK140 OTS MC
You have the wrong kind of light for your IGN. It should not be grounded to the panel. It should have two wire connections. Something like this one for Mark V.
OK, I think I see what the problem is now. Rob, I believe your picture is of a 120 ignition light. The 140 installation is different. At first glance it look like the bulb holder is part of the dash panel but if you look carefully you will see that it is insulated with a very thin layer of Paxolin (yellow arrow in picture) the yellow 25 wire should be on the tag marked with a red arrow.
Although my panel is in the car and therefore hard to see, it looks like your 140 picture. I can clearly see how they the wiring worked on earlier models from Rob’s picture, and \how the updated approach in the 140 picture.
I will try to find the 25 screw tonight, and if it’s there, I should be able to simply splice the positive earth module into the white 9 socket wire that runs between the key switch and the ignition light.
Thanks for clearing that up, Eric.
I see a couple of rivets in your picture, which I presume are insulated from the main panel.
Mine has a socket body made of Bakelite.
Yes, they have little insulating washers on the other side of the panel. If the panel is installed in the car it must be pretty difficult to see that the socket is different from the TRF warning light and unless you were looking for them you could easily not notice the insulating washers - they are hardly any bigger than the rivet heads.
I hope that John will find the missing yellow wire on the screw tag. I can’t believe it isn’t there otherwise the light wouldn’t work.
It looks as though you have to remove the Field connection from the control box and connect it to one side of the Ignition light. The other side seems to be connected to ground via a relay that closes when the ignition is turned on. I suppose the Dynamator has phoney F terminal which is really another dioded feed from the alternator.
Eric,
I have a followup question for you. I have finally installed the Dyanamator and the positive earth module we discussed and it’s producing current, and the red idle light seems to work correctly illuminating at low revs around 700.
However, the amp meter shows neutral most of the time and shifts to negative or discharge when the headlights are turned on. A voltmeter shows the battery at 12.1 volts at rest, and 13.7 volts running around 2400 revs with the lights off, this drops to 13.4 volts with the lights on.
Any thoughts about what might be happening? Is something possibly wrong with my wiring, or can the Amp meter in the panel simply go bad?
Thanks,John 1956 XK140 OTS
Interesting problem. My first thought is that 13.7 volts is at the lower end of what I’d expect with a healthy battery. I’d have thought something significantly over 14 volts would be nearer. What voltage do you get if you measure directly on the Dynamator D terminal? Are you sure the battery is good?
John.
A fully charged healthy battery with no draw should be 12.65 volts. 12.1 tells me your battery is 1/2 charge, you may want to check your cells with a hydrometer ,all fully charge cells should read 1250 to 1275.
