Waldi Posted July 15, 2022 Report Share Posted July 15, 2022 My remanufactured alternator was not charging initially after my restoration. I left it for some time (had other things on my list), and the issue disappeared. I suspected the brushes were not making a good contact when new, but since it worked ok, I did not investigate. Could this be your issue? Maybe have a look at the brushes, see if they slide freely? Waldi Quote Link to post Share on other sites
qkingston Posted July 20, 2022 Author Report Share Posted July 20, 2022 OK, next chapter in this sorry tale. Newly reconditioned original Lucas alternator from Powerlite, installed. Started up and ignition warning light remained on!!! I cannot believe that this alternator is defective, and the fact that the previous Bowers supplied alternator which I had returned believing defective, was tested ok by them. I tested the battery voltage as the engine was running, it was a steady 12.5V when idling, only increasing to 12.6V when throttle blipped. Strangely, when I switched the engine off, the voltage very slowly climbed to 12.7V and stayed steady. Taking all the previous comments into account I believe there must be an earth somewhere; before this started happening everything was working ok, and as previously described, new loom etc during rebuild so I don't believe it is an age/fatigue related issue Any help appreciated David Quote Link to post Share on other sites
Waldi Posted July 20, 2022 Report Share Posted July 20, 2022 David, The voltage after stopping rises a bit because it is no longer drained by the car (but that does not fix your persisting issue). Looks like the alternator is not the issue after changing it for a reconditioned one (was that tested too?). Since you have a new harness, have you tried making a “new brown/yellow route”, including lamp? This would eliminate the harness. And are you sure the brown/yellow wire is connected to the “field” of the alternator? Waldi Quote Link to post Share on other sites
RobH Posted July 20, 2022 Report Share Posted July 20, 2022 (edited) If the alternator output was that low there is something else going on David. It should go well above 13V when you rev the engine a bit. The battery voltage actually climbing when you switched off is a clue, as that means there was a current drain while the engine was running rather than a charge and the battery recovered to its normal rest voltage when the discharge stopped; so the ignition light is probably telling the truth - there is no output from the alternator. Time to thoroughly check all the wiring connections and continuity, including how the the alternator plug connects if you are using one instead of separate spade connections. Also check the alternator body is making a good earth back to the battery via the engine earth strap. Very silly question - you said the fan belt is tight but is the alternator actually going round at the right speed or is a pulley perhaps slipping? Edited July 20, 2022 by RobH Quote Link to post Share on other sites
qkingston Posted July 20, 2022 Author Report Share Posted July 20, 2022 Thanks guys, a few things to check tomorrow David Quote Link to post Share on other sites
Z320 Posted July 21, 2022 Report Share Posted July 21, 2022 (edited) The warning light gets „12V“ (indeed 12,8 V) from the battery. With the generator/ alternator not spinning or not working it is „on“ because the current flows from the battery ---> thought the warning light ---> to the regulator. With the alternator working the warning light has „about“ the same voltage on both sides and is off. But it is also „on“ on 3 V difference (don’t fix me, could also be some less). Test your battery with the engine off. If it has really only about 12,4 V or less while the spinning alternator gives you 14 V the warning light could also be on. Because the current flows the other direction through the warning light. I would have a closer look on the ground cable of the battery, if there is any issue the alternator also doesn’t charge the battery while a minimum current (for the warning light) could flow. Next check: how old is your battery? 12,4-12,5 V or less is suspicious. Have much success, Ciao, Marco Edited July 21, 2022 by Z320 better understanding (I hope) Quote Link to post Share on other sites
Z320 Posted July 21, 2022 Report Share Posted July 21, 2022 (edited) Just checked: mine is 8 years (!) old, with the engine off the voltage is still 12,9 V It's still in pretty good condition! Edited July 21, 2022 by Z320 Quote Link to post Share on other sites
Mk2 Chopper Posted July 21, 2022 Report Share Posted July 21, 2022 An alternator needs something to start it charging, some earlier ones had a spare exciter circuit, later just used the warning light, so I'm thinking with your current set up the alternator isn't getting the exciter input to start it making a charge output, hence no output and the light remains on. I would do as others suggest and make up new wires for a warning lamp and see what happens. Gareth Quote Link to post Share on other sites
qkingston Posted July 22, 2022 Author Report Share Posted July 22, 2022 ok so this morning, I disconnected the brown wires from the alternator and at the starter solenoid and ran new wires direct from one to the other, also ran a new wire from the 3rd alternator terminal to the ignition warning light and started the car. No change, light remained on and no charge indicated. I then checked alternator casing to earth - all ok Checked 12v on each of the original brown wires reconnected to the starter solenoid, also did a continuity check on each wire, all ok Removed the original ignition warning light and put in place a temporary light, fed from ignition switch and the direct wire from the 3rd alternator terminal. This time lamp remained on but I got a charging rate indicated on the voltmeter and by measurement, increased when throttle blipped Then... I switched the ignition off and the engine continued to run!!!! I pulled the wire from the 3rd alternator terminal to the lamp and the engine stopped! So I'm beginning to think this has something more to do with the ignition switch??? Help! David Quote Link to post Share on other sites
RobH Posted July 22, 2022 Report Share Posted July 22, 2022 It sounds as though the engine continued to run because enough current was passing backwards through the bulb to keep the coil energised when the ignition was turned off. Both are fed from the same point on the ignition switch but so are all the other circuits except the lights ( instruments, indicators, wiper, heater fan etc). You must have used a pretty high-wattage, low resistance bulb for that to happen ? It doesn't necessarily mean there is anything wrong at the switch. Interesting that the new bulb did apparently allow the alternator to run. As mentioned very early on - and repeated by Gareth above, the lamp current will help the alternator to start-up so perhaps the original lamp is not doing that? Still doesn't explain why it stayed lit though. Quote Link to post Share on other sites
qkingston Posted July 22, 2022 Author Report Share Posted July 22, 2022 (edited) Thanks Rob, also took some readings just now, battery voltage at rest 12.8V, when ignition turned to pos 1, voltage dropped to 12.42V. Voltage at the wire feeding the ignition warning light was 12.28V. Does that sound right? What spec should the warning light lamp be? The one I was using was 12V 2W Edited July 22, 2022 by qkingston update Quote Link to post Share on other sites
Waldi Posted July 22, 2022 Report Share Posted July 22, 2022 David, what sort of voltage did you measure at say 2000 -2500rpm? Your battery may be drained a bit, so do not expect 14.5-14.8 V immediately after starting. The voltage at the feed to the ign warning light should be the same as the battery voltage. I suggest to use a lamp between brown/yellow and battery+. I you disconnect this wire (after the ign is switched off), it should stop the engine. Waldi Quote Link to post Share on other sites
RobH Posted July 22, 2022 Report Share Posted July 22, 2022 12.8V is about right for a battery at rest. The ignition circuit takes around 4 Amps when the points are closed, so might explain the 0.5V drop in battery voltage when switched on. The further 0.14V drop at the bulb means there is some small resistance in the wiring and/or switch but it looks about right for 4A drain, 0.035 Ohms is probably normal. The 2W bulb is fine but I am surprised that < 160mA could power the ignition sufficiently to keep the engine running. You live and learn. The interesting point is that the running-on didn't happen with the original bulb and connection. What, then, is different? Can we take a step back to clarify things - is it right that everything was working OK once and that apart from swapping alternators you have made no changes to the wiring since that time? If so it eliminates things like wrong connections or faulty looms etc. Quote Link to post Share on other sites
qkingston Posted July 22, 2022 Author Report Share Posted July 22, 2022 Ok so breaking new is I fixed it. The fault was a non standard bulb holder for the ignition warning light; I had changed the repro bulb holder as it kept falling out of the red plastic shroud and the part quality looked pretty poor. The one I used was a 2 wire holder with a spring metal clip into the metal dash back (phot), what I think has happened is that initially there was enough paint around the fitting hole to insulate the bulb holder and prevent it earthing, over time enough paint rubbed off to allow a path to earth. I swapped over the turn indicator bulb holder, swapped over the LED lamp for a standard one and started up, lamp went out and alternator started charging, battery indicating 14.2V I would never have realised that one good idea could lead to so much effort in troubleshooting, thanks for all the helpful advice, I've learned a lot! David Quote Link to post Share on other sites
ntc Posted July 22, 2022 Report Share Posted July 22, 2022 57 minutes ago, qkingston said: Ok so breaking new is I fixed it. The fault was a non standard bulb holder for the ignition warning light; I had changed the repro bulb holder as it kept falling out of the red plastic shroud and the part quality looked pretty poor. The one I used was a 2 wire holder with a spring metal clip into the metal dash back (phot), what I think has happened is that initially there was enough paint around the fitting hole to insulate the bulb holder and prevent it earthing, over time enough paint rubbed off to allow a path to earth. I swapped over the turn indicator bulb holder, swapped over the LED lamp for a standard one and started up, lamp went out and alternator started charging, battery indicating 14.2V I would never have realised that one good idea could lead to so much effort in troubleshooting, thanks for all the helpful advice, I've learned a lot! David And some said to me on here that the bulb and holder does not affect charging ha ha Quote Link to post Share on other sites
Mk2 Chopper Posted July 22, 2022 Report Share Posted July 22, 2022 That's great news and explains the symptoms perfectly, hopefully it will help future owners with a similar problem. Gareth Quote Link to post Share on other sites
qkingston Posted July 22, 2022 Author Report Share Posted July 22, 2022 Thanks Gareth, your thoughts much appreciated David Quote Link to post Share on other sites
Lebro Posted July 22, 2022 Report Share Posted July 22, 2022 Well done for finding it Bob Quote Link to post Share on other sites
Waldi Posted July 22, 2022 Report Share Posted July 22, 2022 Good catch! Waldi Quote Link to post Share on other sites
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