Area Representative Nick Bassett Posted November 13, 2016 Area Representative Share Posted November 13, 2016 Out for a lovely blat this afternoon when all of a sudden red ignition light comes on and I lose most of my instruments except speedo. Headlights and indicators work fine and instrument lights work too. Engine running fine. Drove straight home...about 12 miles without issue except symptoms above remaining. Checked car over but nothing obvious found. Car is a 94 Supersport. Any ideas? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 13, 2016 Member Share Posted November 13, 2016 Do you have a wiring diagram and a multimeter? This shouldn't be too hard if you have. We need to check if you're charging or not. Check the fuse for the instruments. Check all the wiring and connectors at the battery terminals: disconnect, inspect, clean, and reconnect. Ditto alternator. Ditto dashboard earth. Check that the alternator belt is present and tension about right, and that the alternator isn't loose on its bolts. Jonathan Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 13, 2016 Author Area Representative Share Posted November 13, 2016 Thanks Jonathan.i do have a wiring diagram but no multimeter.New battery fitted last month and all terminals clean and tight. Alternator also fitted properly and belt at correct tension. Odd that I haven't lost speedo?Where is the dashboard earth if that isn't a stupid question?!! There seems to be one which is on the right near to the two windscreen stanchion bolts that could do with a clean.it does seem like an earthing problem to me or perhaps it's a new duff battery?Any other thoughts? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 13, 2016 Member Share Posted November 13, 2016 i do have a wiring diagram but no multimeter.Recommended multimeter: Draper 60792.Odd that I haven't lost speedo?What sort of speedometer? It is a bit odd... unless it's mechanical!Where is the dashboard earth if that isn't a stupid question?!! There seems to be one which is on the right near to the two windscreen stanchion bolts that could do with a clean.That sounds likely.it does seem like an earthing problem to me or perhaps it's a new duff battery?I can't explain it with a single fault at the moment... can anyone else?But I'm always suspicious of recent work...Jonathan Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 13, 2016 Author Area Representative Share Posted November 13, 2016 The speedo is a standard Caterham one.I think the rev counter was hovering around the 900rpm mark but that is all...all other instruments were dead. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 13, 2016 Member Share Posted November 13, 2016 The speedo is a standard Caterham one.I don't know what was fitted to Supersports in 1994: mechanical from the gearbox, electronic from a wheel sensor or electronic from the gearbox.Jonathan Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 13, 2016 Author Area Representative Share Posted November 13, 2016 I wonder if this is a alternator problem after reading this:https://www.lotus7.club/forum/techtalk/ignition-light-0I did stop the car and when I started it again the red light had gone out...then when I booted it down the road it came on again! Perhaps this was the cause of the battery failing last month?I replaced the alternator when I bought the car 9 years ago but have probably only covered 12k since then...surely an alternator would last longer than that?Perhaps I'll call out the RAC and get their view... Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 13, 2016 Member Share Posted November 13, 2016 I wonder if this is a alternator problem...Could be. But how would that explain the loss of the instruments... they should still run off the battery until it's pretty flat.Perhaps I'll call out the RAC and get their view...They should be able to diagnose it quite quickly: they have multimeters! :-)Perhaps this was the cause of the battery failing last month?Could be. It''s not a good idea to replace batteries until you know that the charging is working.Jonathan Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 13, 2016 Author Area Representative Share Posted November 13, 2016 Thanks for your help Jonathan.We went out early last month and got caught in some torrential rain... a thorough soaking. I'll check that dash earth lead first as maybe some corrosion has been created as a result of that wet blat. If that doesn't fix it then the RAC will be the next stop! Link to comment Share on other sites More sharing options...
John Vine Posted November 13, 2016 Share Posted November 13, 2016 "The speedo is a standard Caterham one.I don't know what was fitted to Supersports in 1994: mechanical from the gearbox, electronic from a wheel sensor or electronic from the gearbox."My old 1999 1.8K had a mechanical speedo (driven via one of these from the gearbox), so I imagine yours would be the same. Re the red warning light, this can come on even though the alt is charging correctly, especially if the signal-wire contact at the alt is poor. The way to check is to measure the voltage across the battery at, say, 2-3K rpm. If the value is 14v+, your alt is charging ok.The loss-of-instrument symptoms suggest an earthing fault to me.JV Link to comment Share on other sites More sharing options...
SM25T Posted November 13, 2016 Share Posted November 13, 2016 Main earth behind dash is on a stud by the wiper motor above passenger knees. Link to comment Share on other sites More sharing options...
Stridey Posted November 13, 2016 Share Posted November 13, 2016 If you suspect the alternator and it got a recent soaking, do check if you have the wires in a plug enclosure.i suffered alternator failure after a soaking, fixed by buying a plug enclosure for the wire, that use the clip you probably have on the back of the alternator. It's very exposed down there to the elements. My 7 just had wires going straight to alternator with no real protection.Of course, if you have the plug, ignore my suggestion! Link to comment Share on other sites More sharing options...
Duckpit Posted November 13, 2016 Share Posted November 13, 2016 Speedo on my 95 Supersprint is mechanical, to see if its earth just run a wire from the chassis to a rivet on the panel, suspect its not Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 13, 2016 Author Area Representative Share Posted November 13, 2016 Thanks Duckpit... do you mean you suspect it's not earthed correctly or that's not the problem? ! Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 13, 2016 Member Share Posted November 13, 2016 The problem with the instruments could be a bad earth, but it could be something else.I don't think that type of earth fault would cause the ignition warning light to stay on.Jonathan Link to comment Share on other sites More sharing options...
revilla Posted November 14, 2016 Share Posted November 14, 2016 What kind of alternator warning light do you have? Is it the little LED built into the tacho or do you have a separate warning bulb on the dash on a car of that vintage?All of the instruments are powered from one fuse (certainly on later cars, Fuse 2, 10 amps). If this blew you would use all the instruments. And if the warning light was a bulb rather than an LED, also powered by the same fuse (as I think it would be), the loss of the supply voltage here would cause the alternator to back feed through the warning light, partially powering all the instrument systems and causing the alternator warning light to glow (I don't see that it could do this with an LED as they only pass current in one direction, unless they have some internal diodes to make them reversible). This could quite easily give you partially working tacho.Check that fuse!What happens when you switch the heater fan on? This is normally on the same fuse. If that fuse has gone, the heater fan won't work properly and the light will probably increase in brightness when the motor tries to draw current.PS: On an engine test rig I'm running, when I first built it, back feed through the alternator warning light was enough to power the ECU and engine electrics at idle after I switched the ignition off; I had to add an extra large "power on" bulb to pull the voltage down to get it to actually switch off! Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 14, 2016 Author Area Representative Share Posted November 14, 2016 Thanks Revilla.Alternator warning red light sits in the dash between the speedo & rev counter - I think it sits above the full beam blue light.I will indeed check & replace fuse 2 - plus any others.Now that you mention it, I think the fan did stop working - not certain, but pretty sure. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 14, 2016 Member Share Posted November 14, 2016 Before you change anything please could you have another look at the red warning light: Is it ON when the ignition is on and the engine isn't running? (As normal.) Is it fully bright when the engine is running?ThanksJonathan Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 14, 2016 Author Area Representative Share Posted November 14, 2016 I will check tonight Jonathan - thanks Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 19, 2016 Author Area Representative Share Posted November 19, 2016 Fixed... it was the simple 10amp fuse that had blown. Thanks to everyone for advice given. Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 19, 2016 Author Area Representative Share Posted November 19, 2016 Fixed... it was the simple 10amp fuse that had blown. Thanks to everyone for advice given. Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted November 19, 2016 Author Area Representative Share Posted November 19, 2016 Fixed... it was the simple 10amp fuse that had blown. Thanks to everyone for advice given. Link to comment Share on other sites More sharing options...
John Vine Posted November 19, 2016 Share Posted November 19, 2016 Result. Good call, Andrew!JV Link to comment Share on other sites More sharing options...
revilla Posted November 19, 2016 Share Posted November 19, 2016 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted November 20, 2016 Member Share Posted November 20, 2016 Well done.Did you check the behaviour of the ignition warning light before fixing the fuse?Jonathan Link to comment Share on other sites More sharing options...
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