Lord Flashart Posted February 26, 2015 Report Share Posted February 26, 2015 Gentlemen, My TR4 has an alternator conversion. Today driving with the headlights on the charge warning light was glowing dimly, on switching off the lights it stops glowing. I experimented a bit and it also glows when the fan is on, so basically any heavy load. I stuck the multimeter in the battery an it shows a voltage of 13.5 volts with the engine running which seems healthy enough. Any ideas? Paul Quote Link to post Share on other sites
graeme Posted February 26, 2015 Report Share Posted February 26, 2015 Hi Paul, Is it a Lucas 15/18 ACR type? It is probably the regulator starting to fail. It is easy to change one, you need to identify which one you have as there is two/three & four wire types, all readily available on ebay if not at your local Lordco. There is a good article here. http://vintagetriumphregister.org/alternator-repair/ Cheers Graeme Quote Link to post Share on other sites
Lord Flashart Posted February 26, 2015 Author Report Share Posted February 26, 2015 Thanks Graeme I'll whip it off and get it tested. Damn thing has only been on the car a year. Came from lordco and might even still have some warrenty. Paul Quote Link to post Share on other sites
RogerH Posted February 26, 2015 Report Share Posted February 26, 2015 Hi Paul, when you tested the battery with engine running (13.5 volts) did you have the headlights on? if not then the extra current draw will bring the volts down - and the ig light on. Are ALL of your earth cables attached on clean metal. Have you got an earth cable from battery direct to engine (they normally go battery body, chassis, engine) there is no positive link between body and chassis. Roger Quote Link to post Share on other sites
littlejim Posted February 26, 2015 Report Share Posted February 26, 2015 Have said before a very old bulb in the warning light can produce the symptoms too. Worth a swap before getting on to the hairy chested stuff. Quote Link to post Share on other sites
Lebro Posted February 26, 2015 Report Share Posted February 26, 2015 Can't see how a "very old bulb" can do this. 13.5V is too low for a battery on charge, was the engine on tickover, or higher ? at say 2000 RPM you should see nearer 14.5 V The bulb is effectively wired between the battery (via ammeter, ign switch, & lots of wire) & a rectified O/P of the alternator (via more wire). If all the diodes in the alternator are OK, then once charging (higher than tickover revs) the two voltages across the bulb should be pretty much equal. hence light goes out. If light is on then there is a voltage across it, so suggest do some checks to see which side has the higher voltage (should be alternator, but may not be). Bob. Quote Link to post Share on other sites
Lord Flashart Posted February 26, 2015 Author Report Share Posted February 26, 2015 Cheers gents, The 13.5 volts was with the engine revving, but was the same at idle. I'll have another tinker and report back. Paul Quote Link to post Share on other sites
Lord Flashart Posted February 26, 2015 Author Report Share Posted February 26, 2015 Had the alternator tested locally and it appreas to be fine. I suppose it must be in the wireing somewhere. I'll refit the alternator and start tracing wires! Paul Quote Link to post Share on other sites
littlejim Posted February 27, 2015 Report Share Posted February 27, 2015 (edited) Lebro, beautiful explanation of why it is impossible. But as reported earlier had a friend with the same problem on his Datsun. First auto electrian listed all the things he would replace to fix it, but couldn't do it for a couple of weeks. Second auto electrician replaced the warning light bulb, patted friend on back when asked the cost, and off we went with no light glowing. Have no idea why. If you want some WAGs put forward, maybe the old oxidised globe filament (tiny bit of O2 available in the bulb?) was responding to minor current imbalances that a fresh globe wouldn't glow for. Suspect the production and use of electricity although theoretically nice and steady, has a few waves and wobbles in it practice that can be detected. Cheap thing to try even if it doesn't work. Edited February 27, 2015 by littlejim Quote Link to post Share on other sites
RobH Posted February 27, 2015 Report Share Posted February 27, 2015 Just a silly question but no-one above seems to have asked it--- are you sure the fan-belt wasn't slipping ? As for the 'old bulb' thing - perhaps the auto electrician that littejim quotes above just put a higher voltage bulb in ! Rob Quote Link to post Share on other sites
john.r.davies Posted February 27, 2015 Report Share Posted February 27, 2015 Had exact same problem, gently glowing ignition light and poor charging. I went for more and more powerful and power sapping alternators to no avail. Until I realised, as suggested above, that there was no engine block earth. A length of stater cable from block to battery earth - it's the starter earth too! - sorted it. John Quote Link to post Share on other sites
Lord Flashart Posted March 3, 2015 Author Report Share Posted March 3, 2015 I refitted the alternator and the fault has disappeared for now. I'm wondering if it was just a bad connections somewhere. I'll see if it returns! Paul Quote Link to post Share on other sites
TR 2100 Posted March 3, 2015 Report Share Posted March 3, 2015 Flash - Glad it's sorted. Maybe your 4 was just looking for a bit of attention?! AlanR Quote Link to post Share on other sites
MikeF Posted March 3, 2015 Report Share Posted March 3, 2015 A possible explanation for why replacing an old bulb fixes the issue is metal oxide rectification. Copper oxide can have semiconductor properties as can oxides of cadmium contaminated tin (quite possible in those days). However its not very likely. More likely just unscrewing the old bulb would tend to break down some oxide /soil and of course a new bulb would have clean threads so the circuit is very likely to work better. Just cleaning the old bulb thread and contacts would probably be as effective. IMHO on our older cars, with any electrical issues the first thing to check is earth connections, and the second thing is all other connections in the circuit! Mike Quote Link to post Share on other sites
Lord Flashart Posted March 4, 2015 Author Report Share Posted March 4, 2015 Cheers guys. Alan, my TR gets lots of attention! So much that my wife calls it my mistress! I'm now thankfully achieving a decent level of reliability as just about everything on the car has been changed with NOS parts. Now just to fit my new overdrive gearbox, hopefully that doesn't open another can of worms!!! Paul Quote Link to post Share on other sites
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