Mystery glow of the Alternator Light

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kiwi
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Mystery glow of the Alternator Light

Post by kiwi »

Before you say it is the Alternator let me try to cover some bases and probabilty because this dont seem that obvious to me.

I have noticed when the TZS does not start first time which is often the case after several days and cold weather starting (yes look into the carb another job), that on the final succesful attempt the car labours to start. I put this down to the starter motor labouring but that means its looking for juice so why on the first start when the cars started from warm dont seem to get that problem.

The alternator circuit should be charging fine in fact it was when I had it checked out and complete overhaul of the brushes.

Yet couple nights back I noted a dull glow of the alternator light when the demister fan was on. something not quite right but what? There is a drain causing the light to come on, A drain causing the starter to labour from cold. Battery does not go flat though.
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Post by mat_fenwick »

I've had this before on a couple of different vehicles yet was getting a good charging voltage. The charging light has an ignition supply on one side, and when the engine isn't running is earthed through the alternator. When everything is working correctly and engine is running you get say 14V each side of the bulb and hence it doesn't light.
What was happening was that the blower fan was dropping the ignition circuit voltage slightly (due to resistance somewhere in the circuit), to say 13V and hence there was 1V across the bulb so it glowed. On one car I went through the loom and replaced any poor connectors - even replaced the fuse box with a new one which made the biggest improvement but still it remained slightly. It was eventually cured by putting a diode in the wire from the charging lamp to the alternator, so current could only flow towards the alternator.
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Post by docchevron »

My TD does exactley the same thing. The light gets slightly brighter the faster the motor is spinning.

As Mat said, although I just live with it and haven't yet had any starting / charging issues.
Although there's no ignition system on the diesel so the charging system has a slightly easier life...
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Post by CaM »

alternator regulator and/or brushes. VERY common fault on PSA product. I've had a few pugs that do it, three bx's and experienced a few friends cars that do the same. since you've done brushes it'll perhaps be the reg.
my 205 ran about 40'000km before it finally gave up the ghost. mate's bxgti did about 10k before no more charge..
my ph1 bx did it last week but has stopped since replacing the hydraulic belt... maybe the tap with the heel of my hand to de-tension the alternator shifted something?
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electrokid
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Post by electrokid »

something not quite right but what?
The alternator is a 3 phase AC device with the output rectified through diodes to give you DC to charge the battery. If the diodes in one or two of the phases blow then it will only be charging from the one or two phases that are working properly but the alternator light will receive power during the phase or phases that are not working - so it will be pulsed - but at too fast a rate for the bulb to resond as a 'flicker' so it will just glow - particularly when a heavy load is applied to the electrics. So this might be the problem.
My TD does exactley the same thing. The light gets slightly brighter the faster the motor is spinning.
Some time ago I shelled out many pictures of The Queen for a high output recon alternator for a Granny. At tickover it was fantastic - after 2000 rpm I had the ign light on ! Stripping it down it looked fine - until I spinned it - the bright shining commutator was eccentric ! At speed it was throwing the brushes off !
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electrokid
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Post by electrokid »

I've found something which may be relevant. In the BX workshop manual 'BX 19 GTI Table of Bulbs' the charge indicator warning lamp is listed as 3W wedge base = 10mm and the bulb type listed as 'W3W'.

I have the instrument pod from a 16i which has an 82 ohm resistor in series with the ign lamp - don't know if that's the same value on the 19 GTI but having a 3 w bulb instead of the normal 1.2w would make it less inclined to glow at the wrong time.

Does anyone know if theres a 10mm wedge bulb holder that would fit in the same size hole in the PCB as the one for the W5/1.2 bulbs ?
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Post by kiwi »

Since this got bumped up

The problem I was experiancing "seems" to have resolved itself. What exactly that means is anyones guess.
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electrokid
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Post by electrokid »

Has your weather gone above freezing yet ?
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Post by kiwi »

electrokid wrote:Has your weather gone above freezing yet ?


:lol:

Daytemps rarely (as in once in several years) go below freezing here ;) Just get heavy frosts but the days soon rise back to double figures, quite nice going from -7 to +16 in 6 hours 8)

Conditions on the night in question were producing condensation so possibly creating a short somewhere.
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Post by Stinkwheel »

I totally agree with elctrokids one or two bad diodes in the rectifier part of the alternator.

My solution, ignore it.

99.89% of S2 CX's ive owned have done it (for instance when the heater blower was used at high speed at night) They never ever actually gave trouble or didnt charge.
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Post by Vanny »

I've had similar before, resistance in the wire from the bulb to the alternator was pretty high. I changed the whole lot out, problem went away. Don't know if the wire had broken down or (and more likely) there was a very dirty contact in the line.
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electrokid
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Post by electrokid »

I totally agree with elctrokids one or two bad diodes in the rectifier part of the alternator.

My solution, ignore it.
Can't say I'd do any different :-)
I've had similar before, resistance in the wire from the bulb to the alternator was pretty high. I changed the whole lot out, problem went away.
... and possibly fixed a dodgy connection while doing so - interesting though.
Daytemps rarely (as in once in several years) go below freezing here
I was thinking perhaps a bit of grease or water on the slipring brushgear - iced up or grease not allowing the brush to float properly.

But then if the problem has gone away... I usually call that 'job done' :lol:
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Post by kiwi »

Freezing temperatures did not play into it to be honest. Just on the starting which I think I can put that down to a starter motor becoming lazy (wearing out).
My spare starter went into the TRS when the starter failed with little warning and spins over quicker even though it was a second hand one from the 16 I scrapped. Might big might swap over the starters one day to see if any differance...but the old adage dont fix it until it breaks comes to mind. :wink:
I was thinking perhaps a bit of grease or water on the slipring brushgear - iced up or grease not allowing the brush to float properly.
It happened on a warmish night (above freezing) lot humidity around and the car had been standing for a week (in the garage). The only reason I flicked on the Aircon was to speed the demisting which came about rapidly.

My thoughts are the brushes may have stuck as it had been refurbished so may not havew been sitting correctly or just moisture in the contacts.
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electrokid
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Post by electrokid »

The only reason I flicked on the Aircon was to speed the demisting which came about rapidly.
That plus the battery still being charged at a high rate could bring on the light anyway.
My thoughts are the brushes may have stuck as it had been refurbished so may not havew been sitting correctly or just moisture in the contacts.
My thoughts too - brushgear should be bone dry of course no lubricants -the graphite content in the brushes do the lube.

Ok here's one straight off the wall - check your engine mounts ! :-)
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Post by Dollywobbler »

Ah, knew I'd seen this thread somewhere. First drive in the dark in my CX tonight and guess what? The alternator light is glowing very slightly...

Mind you, it could well be due to the belt tension, which is slacker than a yokel's jaw.
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