[TheVarix]

Hi,
I have a 2005 Alfa 156 1.9 JTDM. Yesterday I went for a ride at night time and when I turned the lights on, an orange warning light appeared on the rev counter. I checked the car's manual and the lights that could trigger this warning light are: sidelights, brake lights, rear fogs and number plate lights. I've checked all lights, including dipped beams, indicators and front fogs and they all work! I'm confused... I know nothing about car electrics but could it be that one bulb is about to go, changing the resistance of the circuit and triggering the warning light? I've checked the car with my handheld obd scanner and there were no errors thrown. Any suggestion will be much appreciated!

 

[Upex]

Are any bulbs led? As they can trigger warnings even when working fine, if the current too low.

Check all bulbs, numberplate ones are easy to miss, but also internal as well. I had a dome light go and that tripped a warning. Also reverse lights which often don't get checked when having a quick look round and the rear fog.

I'd say it's unlikely to trigger until the bulb actually pops, but as above, leds can trip it when burning bright due to naturally having lower current / resistance.

 

[TheVarix]

Thanks for the reply! No leds as far as I can tell. I don't think I've checked the reverse light and some of the interior lights. Will give that a try.

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[mdb188]

Sounds daft but I've heard this is a problem with the rev counter, or maybe I dreamt it... Sure it sounds familiar though

 

[TheVarix]

Sounds daft but I've heard this is a problem with the rev counter, or maybe I dreamt it... Sure it sounds familiar though

Thanks! I've found an old post that refers to what you're saying:

if you check your lights and they all seem ok the check the rear brake lights when its dark, if there is a faint glow from one of your bulbs,it means your diode has blown which is part of the rev , counter if thats the case as mine was then change the whole rev, counter you can pick them up cheap enough and is easy to change, i have also herd of people stripping down the rev counter and replacing the diode.

However, both brake lights seem bright and none seems dimmer than the other...

 

[TheVarix]

Well, I can confirm now that every single light in the car is working: interior and exterior. I am really confused...

 

[Upex]

And no replacement leds?

We're all the bulbs the right wattage, as that could cause different readings and trip it.

If both of above ok, then sort of having missed one, ie a second reverse or fog lights type thing, then all I can think of is control units and such that handle the signals, but not familiar with them to even star directing I'm afraid.

Have you tried cleaning all bulb contacts? I have a reverse light in my merc that has corrected contacts on the rear cluster board. When I clean them up, it works ok, few days or weekso, and light comes in again, both if the reverse still lights or not. Might be worth a shot? And check earthing point are clean to.

 

[TheVarix]

So do you think is an ecu problem? I have recently bought the car and reached an agreement of a partial refund with the dealer as the ECU will need investigating for a different reason (sporadic crankshaft position sensor error)

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[Upex]

Not familiar with the controls of your car, but all these signals pass through some sort of module computer thing somewhere, at least 1. So, if all bulbs are working, and none are led or wrong wattage to spoof the computer in thinking there's a bulb out, then the signal to illuminate that indicator is incorrect, which would point to the controls to me, ie the ecu or module(s) that this circuit is driven by either being a touch on the duff side, or getting duff information that makes them think there's a bulb out, like a crappy connection or broken wire etc. Or, the dash indicator bit if fault, but doubt that as fairly simple.

 

[TheVarix]

Hi again,
Thanks for the reply!
After checking again, it turned out to be the driver's side sidelight that was gone.I've no idea how the hell I missed it but I did. I think on Monday I'm going to go to spec savers to claim my money back...

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[Upex]

Your not the first, nor be the last to do it. I coped with a warning light for a long time, and it was a numberplate light, and I'd checked everything many times (except those lol).

Have had the warning in my slk for months, but know that's the reversing lights, fixed it three times and keeps happening, so I've left it be now lol, i just tripple check for others when reversing lol.

Glad you found it.