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Stag, 2500 & 2000 Forum

Ignition light does not come on / Alternator Drain

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ham204mg Avatar
ham204mg Mario Psaila
Mosta, napp, Malta   MLT
Hi Guys, I am an owner of a '72 white Stag. Please bear with me with my ongoing saga with the car's electrics.
On the whole the car is in pretty good condition and my recent modification to an external electric water pump has made it more reliable. When I bought the car the ignition light did not come on and I did not make much of it, thinking it being a blown bulb. The PO had also told me that the battery would drain overnight if I 'did not close the door properly as the puddle light would still be on'. Again, as i am in the habit of disconnecting the battery when the car is not in use so had no opportunity of having the battery drained in the morning.
When I fitted the EWP, I had to locate it in the place where the alternator is originally fitted, with the alternator being fitted on the other side. I also bought an uprated alternator from EJ Wards together with an extended harness. The first of the problems started when I replaced the old alt harness with the new by simply using the old connections from the car's harness into the new alternator harness. I also checked the instrument cluster and found that the ignition bulb was alive and well and responded to a 12v burst! When I started the car, I found that the ignition light did not come on when I turned the key and the alternator was not charging (tested with a meter and also through the voltmeter on the dash). Seeing that there was another connection in the car's harness, I switched the brown/yellow thin wire to that connection and the alternator was then charging well >13v. Again the ignition did not light up when I turned the key.
I happened to leave the car 's battery connected one day and sure enough, the next morning it was totally drained measuring 1.5v at the meter! After recharging, I removed the earth lead and checked the amperage between that and the battery terminal and it was reading 3 amps, a very heavy drain. First I removed the fuses, one by one (no change in drain). Then I removed the alternator plug and the drain fell to 0. Thinking it was a faulty diode, I took the alternator to an electrician and he confirmed that the alternator was good, there was no drain problem with it and all diodes are fine!
I am sure that the ignition light not coming on and the alternator drain are somehow connected. I am not sure why there were two connectors in the car's harness in the part where they connect to the alternator harness. In my first try to reconnect the harness I definitely used the same connectors as were used with the old alternator, but as already explained, the new alternator failed to charge.
So the situation now is that the battery has a 3 amp drain if left connected and the ignition light does not come on when I turnt he key. I am now quite at a loss as to what to do next! The only thing I can think of is to wire directly from the ignition bulb to the thin brown/yellow line and see what happens then. Any other suggestions please?

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Looking at the ROM, it appears that a 72 would originally still have the early 11AC alternator, with the external control box and external voltage regulator. Is that what your car had originally? And does the 'uprated' alternator have an internal regulator ? If so, you may have a small amount of re-wiring to do, and some wires that will remain unused.

With the 11 AC, the 'ignition' light is controlled by the control box mounted to the shock tower. The same wire runs to the alternator, and the voltage regulator mounted lower on the body.

From the sounds of your constant drain, I would guess that you've gotten the small brown wire (which is hot all the time) connected to the alternator terminal for the ignition lamp; which means it is supplying power to the field all the time (hence the 3 amp current drain). You'll need to disconnect that, and identify the terminal that needs the constant power (aka battery sense line) if in fact your new alternator needs it (some do, some don't). Then find the wire to the ignition lamp, and try connecting it to the alternator terminal that did have the constant power. The wires to the old VR & control box can be disconnected, but make sure they cannot touch each other or anything else.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

ham204mg Avatar
ham204mg Mario Psaila
Mosta, napp, Malta   MLT
Randall, many thanks for your reply.
Problem has been solved far more easily than I expected. Yday I decided to isolate the thin brown/yellow wire and checked the battery drain again. This time it went to zero. That narrowed down the possibilities considerably. I then replaced the ignition bulb in the cluster just to make sure that it is a working bulb. Reconnected the br/yellow wire to the original connection in the car's harness (see my post above) - the one which when connected the first time to the new alternator, produced no charge when starting the engine! I was expecting the same result this time round but amazingly, the ignition light came on when I first turned the key and the voltmeter started climbing when I started the engine! I am a bit baffled how it has sorted itself out but am very happy with the result and definitely won't complain! I left the battery connections on and this morning the battery read a healthy 12.6v

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Good, glad you got it sorted. My guess is that your alternator is one of the ones that requires some current through the dash warning lamp to get itself started after the engine is started; and either the old bulb was bad or not making contact with the socket.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

ham204mg Avatar
ham204mg Mario Psaila
Mosta, napp, Malta   MLT
Yes in fact it is one of those that need an exciter. Thanks again for your input! smiling smiley

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