ECR Posted January 26, 2012 Share Posted January 26, 2012 A bit of history first I have just rebuilt my car (including tidying up and re taping the loom) and just pulled the engine out (twice) to cure a faulty head gasket. In preparation for an upcoming trip I decided to rectify a problem which I had, before the strip down, with my tacho which was occasionally dropping to zero for a very short time then re engaging. This seemed like a faulty feed. During my investigation of this I discovered that my Denso alternator wasn’t charging and I noticed that I had no ignition light at start up (not sure how long it had been like this ...). The feed for the tacho looped off the rear of the ign warning light (green wire which itself seems to loop along the switches/gauges) and tracing this back I found a connector had come off the heater fan switch. Reconnecting this restored the feed to the ign contact on the rear of the alternator (which had shown zero volts before ) and gave me a charging alternator and a much more stable rev counter. The rev counter would still occasionally hiccup so I wired a new feed from the rear of the master switch and the rev counter is now stable. I can run the car like this but I have no ignition warning light and this bothers me… I have 2 wires to the rear of the ign warning light, one brown/yellow and a double green. With the ign on and both disconnected from the light I get 0 volts on the brown/yellow and 2.5 volts on the green . Presumably I should see 12volts on one of these but which one. My wiring diagram (1990) is buried in my house move boxes and wont surface till we unpack later this year and in any case the wiring has been subject to repair/mod over that time so may not be too reliable. Help needed to re establish my ign warning light please ….. (which may have been lost during the rebuild….) Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 26, 2012 Share Posted January 26, 2012 Hi Roger Brown/yellow to smallest of three adjacent tabs on alternator, the green loops all over the place on the circuit diagram but ends up at a fused +12V supply (Heater and Instruments). You should be getting +12V on your green wire, not 2.5V. The brown yellow should go to +12V when the alternator is running, thereby causing the bulb to go out. Did you sort your head gasket okaY? Paul Edited by - Paul Deslandes on 26 Jan 2012 14:07:06 Link to comment Share on other sites More sharing options...
ECR Posted January 26, 2012 Author Share Posted January 26, 2012 Hi Paul First, I've sorted the low supply to the green (2.5v). The (redundant) heater fuse had blown. I now have 12v to all the greens. However I still have no ign light... If I have 12v to one side of the light it would appear that the brown/yellow is broken somewhere I'll check to see if the brown/yellow (when disconected from the lamp) gives 12v when running if not I guess that would confirm a break ? Head sorted thanks and engine appears fine. Thanks for your help Edited by - ECR on 26 Jan 2012 15:09:05 Edited by - ECR on 26 Jan 2012 15:11:45 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted January 26, 2012 Member Share Posted January 26, 2012 Have you checked the bulb is OK, and the contacts in the bulbholder are OK? Probably worth doing that before you move onto more complicated possibilities. Then stick a meter on the alternator terminal that is (should be) connected to the ignition warning light. What's the voltage from there to earth not running and running? Jonathan Link to comment Share on other sites More sharing options...
ECR Posted January 26, 2012 Author Share Posted January 26, 2012 Have checked the bulb Jonathan and it's ok. No voltage frm the brown/yellow wire at the dashboard end with the engine running. I'll check at the terminal on the alternator as you suggest. If that's ok, I'll probably run another wire and use that till the engine next comes out and I can open up the loom. It'll have to wait till tomorrow now as failing light stopped play (can't wait til I get into my new garage and can switch a light on !) I really appreciate your help Edited by - ECR on 26 Jan 2012 16:01:34 Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 26, 2012 Share Posted January 26, 2012 The ignition warning light feed from the alternator is usually a separate rectified output, used to act as a charge warning light supply and to supply the regulator circuit module. It should be zero when the alternator isn't running, with or without the ignition on, and +12V 'ish when it is running. If the wire's okay and nothing else is wrong then its likely a faulty regulator in the alternator. I have had one of those small terminals crack and go open circuit. If you remove the plastic cover you might be able to locate the fault and wire-bridge solder it to effect a repair. Glad to hear that the engine's okay. Nasty scare for a while. Link to comment Share on other sites More sharing options...
ECR Posted January 26, 2012 Author Share Posted January 26, 2012 The Nippon Denso alternator has it's regulator on a replaceable module and this was the first thing I replaced so I know it's good. It seems very likely that it's a broken wire I think ... Link to comment Share on other sites More sharing options...
ECR Posted January 27, 2012 Author Share Posted January 27, 2012 Still have no ignition light and would appreciate your thoughts. Below is all the information I currently have ..... There are 2 faston terminals on the rear of the alternator and 0ne large ring terminal on top One of the faston terminals is marked “IG” Bulb in ignition light has been checked and is working With both of the faston terminals removed from the rear of the alternator but with the ring terminal still connected. Ignition on engine not running IG 0V at the terminal on the alternator Other 0V at the terminal on the alternator With both of the faston terminals removed from the rear of the alternator but with the ring terminal still connected. Ignition on engine running IG 0V at the terminal on the alternator Other 0V at the terminal on the alternator With both of the faston terminals removed from the rear of the alternator but with the ring terminal still connected. Existing wiring to ignition light connected at dashboard end Ignition on engine not running At the alternator end of the wire feeding the IG terminal 12V At the alternator end of the wire feeding the Other terminal 12V With both of the faston terminals removed from the rear of the alternator but with the ring terminal connected. Brown/Yellow wire to ignition light DISconnected at dashboard end Ignition on engine not running At the alternator end of the wire feeding the IG terminal 12V At the alternator end of the wire feeding the Other terminal 0V With both of the faston terminals removed from the rear of the alternator but with the ring terminal connected. Existing wiring to ignition light connected Ignition on engine running At the alternator end of the wire feeding the IG terminal 12V At the alternator end of the wire feeding the Other terminal 12V Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted January 27, 2012 Member Share Posted January 27, 2012 Quoting ECR: There are 2 faston terminals on the rear of the alternator and 0ne large ring terminal on top One of the faston terminals is marked “IG” Bulb in ignition light has been checked and is working With both of the faston terminals removed from the rear of the alternator but with the ring terminal still connected. Ignition on engine not running IG 0V at the terminal on the alternator Other 0V at the terminal on the alternator With both of the faston terminals removed from the rear of the alternator but with the ring terminal still connected. Ignition on engine running IG 0V at the terminal on the alternator Other 0V at the terminal on the alternator There's something wrong with the alternator. See Paul's and ECR's posts above. Quoting ECR: With both of the faston terminals removed from the rear of the alternator but with the ring terminal still connected. Existing wiring to ignition light connected at dashboard end Ignition on engine not running At the alternator end of the wire feeding the IG terminal 12V At the alternator end of the wire feeding the Other terminal 12V With both of the faston terminals removed from the rear of the alternator but with the ring terminal connected. Brown/Yellow wire to ignition light DISconnected at dashboard end Ignition on engine not running At the alternator end of the wire feeding the IG terminal 12V At the alternator end of the wire feeding the Other terminal 0V With both of the faston terminals removed from the rear of the alternator but with the ring terminal connected. Existing wiring to ignition light connected Ignition on engine running At the alternator end of the wire feeding the IG terminal 12V At the alternator end of the wire feeding the Other terminal 12V I think that's because: Quoting Mr Locust: The bulb is fed by +12V from the ign switched circuit. Once charging, the bulb terminal of the alternator is raised to +12v so the bulb extinguishes. Quoting CharlesElliott: The ignition warning light works from a feed on the alternator (it sinks to the alternator - so when the alternator is charging, current doesn't flow and the light goes off). Jonathan Edited by - Jonathan Kay on 27 Jan 2012 12:33:17 Link to comment Share on other sites More sharing options...
Brian Soper Posted January 27, 2012 Share Posted January 27, 2012 My series 2 has never had an ignition light am I missing out on something!!! Brian Link to comment Share on other sites More sharing options...
ECR Posted January 27, 2012 Author Share Posted January 27, 2012 Stoppit Brian ! Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 27, 2012 Share Posted January 27, 2012 Roger Assuming that this alternator conforms to the Brise Type 1 nomenclature, IG (Ignition)should be connected to ignition switched +12V, which won't have been fed to original Valeo alternator This is required to provide field excitation. The Brown/yellow lamp wire should got to the L (lamp) terminal (the other fast-on). The big lug goes to the battery, master switch, fuse box, starter WHY etc The last wire (brown/black?) that went to the original Valeo alternator, the one that's separated from the other three, is the battery sense connection which is not used on a 2 + 1 terminal device and should be removed or insulated to make it safe. The other end goes to the battery (or Master switch when fitted). If you have a third terminal marked S (sense) on the alternator, this wire would go here. Paul Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted January 27, 2012 Member Share Posted January 27, 2012 Quoting Paul Deslandes: Assuming that this alternator conforms to the Brise Type 1 nomenclature, IG (Ignition)should be connected to ignition switched +12V, which won't have been fed to original Valeo alternator This is required to provide field excitation. Paul Does that mean that for that type of alternator you have to get the feed to the IG terminal right before the test of looking at the voltage at the lamp terminal is valid? Jonathan Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 27, 2012 Share Posted January 27, 2012 Jonathan yes I think it must, otherwise the lamp would be lit even without the ignition being on. I've been trying to find an internal circuit of a Denso alternator but not succeeded so far. Its different to a Valeo or Lucas type. There must be a solid state switch or a relay internally that switches the lamp terminal to the output when the ignition is turned on. Then, when the alternator runs and produces power, either that terminal voltage rises towards +12V or the switch is turned 'off' and the lamp goes out. Hopefully Roger will get this sorted just by rewiring it slightly. Paul Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 27, 2012 Share Posted January 27, 2012 I've just read back through the entire post and I think that with the main ring terminal connected and the switched IGN lead reconnected and lamp connected to L. Ignition on, engine not running, L terminal should be zero volts and the lamp on. ignition on, engine running, L terminal should be either +12V 'ish or open circuit and lamp off. Link to comment Share on other sites More sharing options...
ECR Posted January 27, 2012 Author Share Posted January 27, 2012 My test indicate that I have 12v to the IG connection on the alternator when the ignition is on and the brown/yellow is disconnected from the lamp at the dasboard end. I also have 12v to the other side of the lamp. If I now run a new wire from L on the alternator to the the lamp that should work I think. I tried this this morning but IIRC I either had no light or a permanent light. It would help if I knew that the alternator was fully functional (I know it's charging ok). I could then concentrate on the wiring. I'm inclined to rig up a seperate circuit and lamp off the car to prove the functioning of the light. Link to comment Share on other sites More sharing options...
ECR Posted January 28, 2012 Author Share Posted January 28, 2012 Having jury rigged a completely new circuit I still get no light so that confirms it's a fault in the alternator. Still charging ok so no immediate need to replace it... Thanks to Paul and Jonathan FrrrrrrPPPP to Brian Soper 😬 Edited by - ECR on 28 Jan 2012 15:45:37 Edited by - ECR on 28 Jan 2012 17:54:37 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now