Car light intensity varies

[tom1975]

Hi
I have 1983 911sc ,
Lately I noticed that the intensity of the headlights and inside the vehicle lights are changes, what could it be?
My battery is right and I travel quite a lot with the car and no charging problems .
When I increase the rpm does not change in light intensity, it happens alone regardless of rpm...
???

[pete3799]

Could be the voltage regulator is failing.
Hook up a volt meter so that you can monitor it as you drive. I bet you'll see the voltage spiking when the lights get brighter.

[Cooper911SC]

+1 for voltage regulator.

If you have the original external regulator you can just replace it. Will be on the electrical panel at left side of engine bay.

You can check the voltage out-put of the alternator at the battery with a Volt meter. Check battery with car off first. Should be around 12-12.5 volts.

Next start car and check voltage. Should be around 13-13.2. If it is up at 14 or 17 the voltage regulator (VR) is stuck and requires replacement.

Very common problem on the SCs.

Cooper

[tom1975]

thanks guys.
i will check it.
can some one help me with a photo of the voltage regulator and his place ?
i think in my 1983 sc the regulator located near the alternator ???
thanks
tom

[tom1975]

???

[Cooper911SC]

Hi Tom, sorry, working off of iPhone so can't post pics.

On the left side rear of your engine bay is the electrical panel. Should be covered by black plastic panel with 2 wing nut type screws.

The voltage regulator, if still original, is under the cover toward the front.

It will be a small silver metal box about 3"x3"x1"thick. The top is slightly domed.
It will have a wrap of tape at the base and will have a 3 pin electrical connector at the bottom.

Porsche started using alternators with integrated voltage regulators in 1984 with the 3.2 Carreras.

There was a Tech Service Bulletin that all older models should update to this style as replacement was required. If your alternator has ever been replaced, it might indeed have an integrated regulator.

If it is still original, I would just replace the external regulator.

Hope my description without pic. gets you closer.

Cooper

[Jdub]

I believe your alternator has a built-in voltage regulator. It may be a Valeo?

This thread details some differences in the SC alts of your vintage: 80 SC alternator- correct part?

[tirwin]

83 has the VR built into the alternator. I am having the same issue and other symptoms. I had the alternator/VR tested and they found nothing. I'm still not convinced. From what I've read the VR can start to fail intermittently so catching the problem "in the act" can be hard.

I would do as suggested an get a plug in voltmeter. You can buy one from Amazon for $10 or so. Look for the one that is the Innova brand. If you see it spike you have found your problem. You should also test your battery with the car off, at idle and at 2k rpm.

Also it is working checking wiring for corrosion and bad grounds.

[wwest]

Originally Posted by tom1975

Hi
I have 1983 911sc ,
Lately I noticed that the intensity of the headlights and inside the vehicle lights are changes, what could it be?
My battery is right and I travel quite a lot with the car and no charging problems .
When I increase the rpm does not change in light intensity, it happens alone regardless of rpm...
???

Check the condition of the alternator/battery circuit interconnection at the starter solenoid.

[tom1975]

Ok thanks
I will check and update

[tom1975]

Hi
I checked the battery ,when the car off, the voltmeter say 12.4 and when I start the engine the voltmeter says 14.56-14.6,
After the engine warm it's 14.35

I check with the voltmeter is on V 20 position , it's ok?
So I guess I need to fix the VR ....
I opened the left panel and no VR there ....

[wwest]

Originally Posted by tom1975

Hi
I checked the battery ,when the car off, the voltmeter say 12.4 and when I start the engine the voltmeter says 14.56-14.6,
After the engine warm it's 14.35

I check with the voltmeter is on V 20 position , it's ok?
So I guess I need to fix the VR ....
I opened the left panel and no VR there ....

Two possibilities....

Intermittent short of a battery cell, fairly common, check for one of the 6 cells being lower on water.

Intermittent short within the alternator.....


Poor/loose/corroded engine to chassis ground.

[tom1975]

<
Two possibilities....



Intermittent short of a battery cell, fairly common, check for one of the 6 cells being lower on water.



Intermittent short within the alternator.....





Poor/loose/corroded engine to chassis ground.

Wwest ,You gave me 3 possibilities
Thanks I will check

[wwest]

Originally Posted by tom1975

You gave me 3 possibilities
Thanks I will check

Sorry, flunked 2 and 3rd grades.

[tom1975]

Thanks
Tom