QuestionThanks for your reply. Actually I found the problem after doing some troubl shhoting on the rear of the dash panel. There was a new light socket installed that is vintage correct for the TD. I noticed all of the indicator light sockets had a very thin gauge wire wrapped externally around the socket with both ends ultimatel soldered to the side terminal on the socket. The socket is supposed to be installed from the the front of the instrument panel with a spring, retaining ring and wire clip installed behind the panel to hold the whole assembly in place. I became suspicious of the external wire winding (since it is not insulated from the retainer spring and ring) possibly grounding to the instrument panel. I removed a yellow wire, which terminates at the "D" terminal on the control box. This left only the switched white wire (12V) from the ignition switch connected. The light still stayed on; hence, it was determined the circuit to ground was completed through the wrapped wires that are external to the light socket. This was proved by removing the socket from the instrument panel and reconnecting the wire from the control box. The light now operates as expected. On with the ignition and out when the engine rpms increase indicating proper charging from the generator. Ampmeter is reading correctly. Voltage is correct from the generator. When the indicator socket was reinstalled, it was installed using a small nonconductive washer on the inside of the panel. The retaining spring and ring were not re-installed. The chrome bezel was screwed into the socket from the outside face of the instrument panel holding the socket firmly. I noticed all of the other indicator sockets are of similar design with the spiraled wire solder to the side terminal. Do you have any idea what the functionality is for these external spiraled wires? All of the other idicator sockets are installed from the front of the panel and use the retaining spring and ring.
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The text above is a follow-up to ...
-----Question-----
I am working on a 1953 MG-TD. The ignition light stays on all the time, which would suggest a charging problem. This light gets brighter as the engine rpms increase. The control box is new. I have never seen the ignition warning light intensity brighten to the point where it burns the bulb out, but it does with this car. Is the problem most likely in the dynamo? Should it be replaced?
-----Answer-----
Hi Marie,Do not run buy a Generator as you don't have enough info yet to condemn the generator.
I would first put a volt meter (If you don't have one, they are not expensive at Radio Shack or such a place)across the battery and read battery voltage, Check the belt tension, then start the engine and set the RPM at a fast idle 1500 to 2000 RPM and read the volt meter again while the RPM is up. You should see 13.8 to 14.5 volts. If the voltage goes down instead of up check the polarity of the battery. Originally it was + ground unless the system was changed or the generator was replaced or rebuilt without polarizing the generator. A regulator does not need polarizing. Was the new control box a Lucas? Did the lettering on the connections say: "F" "A" "D" "E" (not necessarily in that order and there may be two "A"s. Was any wiring repairs done when the regulator (control box) changed?
Let me know.
Howard
AnswerHi Marie,
I am glad you found the problem. As for a "spiraled" wire are you talking about an electrical wire wrapped around the light unit? There is no reason to have a spiraled or coiled wire around any of the light sockets. It sounds like something someone did for what ever reason, not MG. It has been a long time since I worked on any of the "T" model MGs but I don't remember any such thing on any of them, TC, TD or TF. could it have been something someone did to make the unit fit tight in the dash because they didn't have the correct parts?
It sounds like they didn't know how the charge light operated (MG called it "Ignition light" all the way up into the MGB)
Back then MG used the regulator to make the ground through the generator for the powered bulb which was grounded when the generator was not charging and this method was carried on into later MGs on to the MGBs with alternators. They did it inside the Alternator on the "B" and "C".
Some times components for older cars are not available so people start modifying.
Now on an alternator system the "Ign" light is used to excite the charging system to start operating when it is turning and if the light burns out the charging system fails to start. On the Jaguar the same system is used except they added a "Shunt" or bypass incase the bulb burns out. This is in the form of a resistor but a long very thin wire would do the same thing. However the way you describe the wire, that would not be the case on your car. In fact the way you describe the connection, it would have decreased charging of the battery by bleeding off some of the current.
I guess all is well that ends well.
Howard
