KarlH Posted July 12, 2015 Share Posted July 12, 2015 The ignition warning light on my car has taken to staying on below 2000 rpm. As is normal it's been working perfectly fine for ages and only started doing this after a long trip to Reading the other day!It's a relatively new brise alternator and a pretty new battery so I'd hope neither of those were at fault.So far I've: checked the battery voltages and it's operating as expected checked all earths, cleaned and tightened etc and following other advice and threads on here checked the wiring to the bulb which appears to be working fine as wellThe alternator is wired into the fan for switched live, if I disconnect the fan the same thing happens - light goes out above 2000rpm, is that to be expected?Anything else I should be checking? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 12, 2015 Member Share Posted July 12, 2015 Yes: there's a recent highly informative thread about Brise alternators, minimum speeds and pulley sizes.Let us know if you can't find it.Jonathan Link to comment Share on other sites More sharing options...
KarlH Posted July 12, 2015 Author Share Posted July 12, 2015 Yep, I'd found that one Jonathan but not sure whether there's anything I can usefully determine from it (other than they don't charge until 2k rom)!When I bought the unit I spoke to Brise and they supplied the correct pulley for a K series installation. It's been working fine, in that the light went out once engine was started, for the last 2 years (relatively little use) and nothing has changed in that time so I don't understand what would cause it to start doing this now! Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 12, 2015 Member Share Posted July 12, 2015 What are the voltages at rest, idle (with rpm), 1,000, 2,000 and 3,000 rpm?Jonathan Link to comment Share on other sites More sharing options...
KarlH Posted July 12, 2015 Author Share Posted July 12, 2015 Haven't tested all those ranges but what I have is: Rest 12.8v Cranking 10v Idling 13.4v 2,000rpm 14.4v Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 12, 2015 Member Share Posted July 12, 2015 I can't explain what's changed.The voltage at cranking is a bit low and might upset some ECUs, but starting isn't your problem.Can someone explain the issue with uisng a fan feed for the switched live feed to the alternator, please? Is this just for convenience in finding a wire? Would a direct feed from the battery be a worthwhile test to see if it makes any difference?Jonathan Link to comment Share on other sites More sharing options...
KarlH Posted July 13, 2015 Author Share Posted July 13, 2015 One of those mysteries!i thought the switched live was there so the battery doesn't get drained, fan wiring used as its close and easy. There are 3 wires on it, one to the light circuit, one to switched live and the other direct to the battery to sense voltage there - I think! Can't remember what colours are what now I've left the garage. Link to comment Share on other sites More sharing options...
John Vine Posted July 13, 2015 Share Posted July 13, 2015 Just a thought....have you checked the alt belt? Is it worn? Is it adjusted correctly?What model of Brise alt do you have?JV Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 13, 2015 Member Share Posted July 13, 2015 And pulley sizes while you're down there. Although that won't explain the change where a slipping belt might.Jonathan Link to comment Share on other sites More sharing options...
KarlH Posted July 13, 2015 Author Share Posted July 13, 2015 Been out all day helping the inlaws move so not had chance to check anything else today. I have checked the belt which looks to be adjusted ok but will get another and change it anyway just to be on the safe side and eliminate that as an issue.I contacted Brise yesterday who were incredibly helpful and said from the voltage readings I'm getting it suggests the alternator is working but sometimes the warning light function of the voltage regulator can fail and not affecting its other functions. They asked what wattage the warning light bulb was in the gauge - I couldn't find anything other than a thread on here suggesting they were 2W is that right? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 13, 2015 Member Share Posted July 13, 2015 I don't know, but I know how to find out without removing it and looking: Turn the ignition off. Disconnect the wire from the alternator to the warning light at the alternator end. Turn the key so that the ignition is on. Measure the resistance (in ohms) between the free end of that wire and the live battery terminal. The power of the lamp (in W) is 144 divided by that resistance. Turn the ignition off and reconnect the wire.(Expert advice, please: how much will that resistance change when the light is on?)Jonathan Link to comment Share on other sites More sharing options...
tbird Posted July 14, 2015 Share Posted July 14, 2015 well brake lights are 21/5 W and the filaments measure 2 ohm and .5 ohm ish using a DVMso that would give a power output of 72W and 288 W resp.for 21 watts you would need a resistance of around 7 ohmsfor 5W you would need a resistance of around 28 ohms but its non Linear so that doesn't help much, other than suggesting that doing the above (JK post) would not give the true wattage But if you put your DVM in series with the bulb and turn the ignition on and measure current then 12 x I will give you the Wattage of the bulb however this may be complicated if the circuit has a resistor wired in parallel with the ignition light which some if not all older systems have .think the usual size bulb is 2.2WTim Link to comment Share on other sites More sharing options...
KarlH Posted September 3, 2015 Author Share Posted September 3, 2015 Gave up trying to diagnose the fault and sent the alternator back to Brise - the repair sheet says there was a vibration factor on the stator wire which has been replaced.I'll be refitting it thise weekend and hopefully all will be well! Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 3, 2015 Member Share Posted September 3, 2015 Hmmm... we'll see! Please remeasure those voltages when it's fitted.Jonathan Link to comment Share on other sites More sharing options...
revilla Posted September 3, 2015 Share Posted September 3, 2015 If "vibration factor" was actually "vibration fracture" then it would be more believable? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 3, 2015 Member Share Posted September 3, 2015 Ah, yes!Jonathan Link to comment Share on other sites More sharing options...
KarlH Posted September 3, 2015 Author Share Posted September 3, 2015 Vibration fracture was what I thought I'd typed so either the useless auto correct changed it or I'm just stupid - no replies to that needed! Link to comment Share on other sites More sharing options...
revilla Posted September 3, 2015 Share Posted September 3, 2015 :) we knew what you meant. Link to comment Share on other sites More sharing options...
KarlH Posted September 6, 2015 Author Share Posted September 6, 2015 Right, all fitted and working.Measurements I took were: Rest 12.9v Cranking 10.8v Idling 14.5v Link to comment Share on other sites More sharing options...
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