Alternator light on when driving at night

[adrians]

Problem ! !

Driven the car for the first time at night !!

Used the headlights for the first time !! (new lights and bulbs)

For the first time I noticed the alternator light comes on ( very dimly ) when the headlights are used. Check it when I got home, the same when idleing.

New fan belt was installed last week when the car was at the mechanic's ( old Tom - been fixing Fiats for 30 years ).

So do I have a problem ? The alternator appears to keep the battery charged as I haven't had to boost or jump start the car in the 9 weeks I've own it !

Therefore is there an internal problem with the alternator ? ( '81 Fpider )

Regards

[rlux4]

Adrian, My bet would be you have nothing to worry about. I had noticed the same thing on a night drive and all it was in my case was light "spill-over" from some neighboring bulb. Without going to a shop to have the charging system checked you could tell if that's it pretty surely by reving the engine when you see the dim light. If it doesn't change intensity brighter/dimmer, then it's probably the spill-over.
Ron

[adrians]

Ron,

I'll give that a try, I'll also remove the main light bulb from the tacho to see if it's 'spill-over' light.

AdrianS

[mbouse]

so, how many amps do your NEW headlights pull? is it possible that you are pulling more amps than your alternator can provide?

does your rheostat for the dash lights still function? it should be possible to turn down the dash lights w/out affecting the function of the indicator lights such as the charging system red light. if you turn down the dash lights and you still see red, you have an issue to attend to.

[adrians]

Mike,

The dimmer rheostat does still work, it actually turned all the way around and clicks and switches the dashboard lights off.

The Alternator light does come on dimly when the headlights are on, (dimmer off) and the light varies in intensity when you rev the engine.

When I replaced the H4 Sealed lights and the new bulbs, I had a long discussion with the Fiat Spare part shop about the correct bulbs. So I think I’m not over taxing the electrical system.

So what parts of the alternator should I look at or a problem with the whole unit ?
( Alternator is located on the intake side of the motor - 2litre F.I. )

Regards

[mbouse]

My bet is the higher the engine revs the dimmer the light, right? and if you turn the radio on with the headlights on high beam, then the red light is brightest at idle.

you've now surpassed my limited knowledge of alternators and charging systems...other than I truly suspect that the alternator is not putting out what the system with lights on is asking for. that is why i suggested looking at total amps the lights are drawing. i am not convinced that the alternator is the culprit yet. you've not proven that.

my catalogue suggests two different model of alternator for the FI cars, one for air and one for no air conditioning. i gotta presume that means different amp production. So, do you have the right one, and what amperage is it spitting out?

Excuse me if i am too elementary, but do you have an ammeter, and do you know how to use it? check the amperage draw at each headlight, and the amperage output of the alternator.

i am also concerned that if you have put in high amp headlights that you very well could be taxing your headlight beam selector switch. Did you put your headlights on a relay circuit to protect that switch from burning out?

[adrians]

I own a multimeter and know how to use it .... so I'll check volts and amps at the battery, alternator and headlights plus I'll add an external load to the electrical systems to see what the effects are !

I'll report back tomorrow !

Thanks & regards

[adrians]

Hi Mike & Co.

Voltages readings present at the battery terminals ( I haven't done amps yet )

Battery with IGN OFF 12.36V
Battery with Engine at Idle No Headlights 13.92V
Battery with Engine at 1800rpm No Headlights 14.01V

Therefore alternator is creating a charge !

Battery with Engine at Idle Headlights On 13.72V
( only 0.2V drop from 13.92V)
Battery with Engine at 1800rpm Headlights On 13.80V
( only 0.2V drop from 14.01V)
Battery when revving the engine 2000-4000 rpm Headlights On 13.80V
( no change of the Alternator light intensity - just on and dim )

Amps next

[lanciahf]

Adrian

Check the voltage at the headlights with the headlights on. Also you should install relays for the headlights to save your switch and provide full power to the lights. Check out the following web page http://users.chartertn.net/jseabolt/elect.htm Scroll down to "Headlight trick:"

Ralph

[adrians]

Thanks Ralph

Rewiring the headlights is on my list, I first have to work out some additional wiring around the headlight wiring loom from the PO.

Will check the volts at the headlights.

Regards

Adrian

[adrians]

Well

I only have 9.68Volts at the headlight socket, so a fair amount of lost !

Looks like a rewire is in order

[mbouse]

If you have that significant of a loss i recommend a two stage wiring project.
1. Brown Wire Surgery to get some fresh 12volt supply to your ignition and other dash controlled components
2. Headlight Relays

Both of these procedures are spelled out in detail at:
http://flumichigan.italiancarclub.com/w ... icles.html

some of the results you can confidently expect to see will be:
a. bright headlights
b. bright dash lights
c. faster wiper blades
d. faster heater fan

If you are seeing weird stuff from previous owners, it is always a good idea to look at what it takes to pull that stuff and get back to basics. You never know when stuff gets shorted out, wired improperly....or what.

[adrians]

Mike & Co.

Will embark on the task of the rewiring of the brown wire etc... next weekend !

Finally checked the amps at the headlight - it's drawing 6.3 amps on the socket, linked with the 3.4Volt drop as well.

So is the alternator up to it ????

Question -What 'makes' the Alternator light glow, what condition of the electrical system actually create the condidtion ? Voltage or ampere inbalance ?

Regards

[mbouse]

So is the alternator up to it ????
Regards

That is the question i am asking you. What amperage is your alternator producing?

if my memory is correct, you should be capable of producing 65 amps with your alternator. older cars, 55 amps.

6.3 left headlight + 6.3 right headlight + all of the side marker lights + tail lights + front marker lights + dash lights + everything else you got going on adds up quickly. If your charging system indicator light is functioning properly, it is telling you that you are riding the edge of trouble. That it is a low glow, and only seen when you use your headlights...you may stay out of trouble for quite a while. Maybe not.

[pope]

Just think of it as another courtesy light.