944 headlights are flickering at idle

[sprocket]

Hello. 

 

my 87 944s has a small annoying issue.  my lights flicker when it's at idle and when I rev up they are fine.  is this a simple issue or a sign that something is failing.

 

thanks.

 

Roch.

[Loren]

Could be a bad ground or an alternator going bad.

Measure the voltage across the battery before and after the lights. Report it here.

[sprocket]

So. Here are the readings.

 

Engine off --- 13V

Engine running --- 16V

Engine running with lights on ---  15v

 

Thoughts?

 

Roch

[Ahsai]

Is your voltmeter accurate? I don't think you can get 13v with the engine off. If it's accurate 15 and 16v are way above the proper charging voltage (13.5-14.5v).

 

You may want to have you battery tested first.

Edited July 16, 2017 by Ahsai

[sprocket]

The voltmeter is brand new.  But I have to admit, I'm not very knowledgeable when it come to electronics.  Do the other numbers make sense?

[sprocket]

I set the meter to 10.  The other options are 2.5 or 50 I believe.  

[Loren]

Are you measuring VDC?  (not AC)

[Ahsai]

You need to set it to a range that is larger than the expected measurement. DC like Loren said. In this case it's 50v. Is it a digital meter? We also need the first decimal reading. E.g., 12.1v vs 12.7v makes a huge difference. A photo of the meter dial might help.

[sprocket]

Here is where I had it set...see photo

[Ahsai]

Wow, reminds me of what I used for my childhood electronic projects :)

 

Sorry to say but this meter won't be accurate enough for this diagnostic purpose. Digital meters are very accurate and affordable these days. This one is nice because it can measure voltage and current drain by clamping the meter around the battery cables. No need to disconnect any circuits.

 

https://www.amazon.com/gp/aw/d/B00O1Q2HOQ/ref=mp_s_a_1_2?ie=UTF8&qid=1500248733&sr=8-2&pi=AC_SX236_SY340_FMwebp_QL65&keywords=dc+current+clamp+meter&dpPl=1&dpID=41sD0XebR4L&ref=plSrch

 

 

 

[Ahsai]

Btw, you need to set your meter to 50 so the full scale sweep indicates 50v.

[sprocket]

I guess I'll have to go buy a digital one then.  Stay tuned!

 

Thanks guys.

 

R

[Ahsai]

This one has a slightly better spec (0.7% accuracy).

 

Re your problem. Have you checked if your battery cables are tight and corrosion free?

 

https://www.amazon.com/gp/aw/d/B00O0HLBJ8/ref=mp_s_a_1_4?ie=UTF8&qid=1500248733&sr=8-4&pi=AC_SX236_SY340_FMwebp_QL65&keywords=dc+current+clamp+meter&dpPl=1&dpID=417d7jMeCYL&ref=plSrch

[sprocket]

Yes.  They are tight and corrosion free.  Someone mentioned maybe a ground wire?  Not sure what I'm looking for in that case or where?

 

R.

[Ahsai]

This? 

 

 

Edited July 17, 2017 by Ahsai

[sprocket]

So that's one of many I presume.  I'll just have to locate them all and clean 'em up.

 

R

[Ahsai]

This one looks like the one from the engine to the chassis. The other major one is the one from the battery to the chassis.

 

I still recommend starting with checking the battery and the charging system first amd see if they are healthy first.

[sprocket]

So should I go to garage?  Or just get proper voltmeter for that?

 

R

[Ahsai]

Saw that you're in Canada but probably it's the same there. In US here, you can bring your battery to any auto parts stores (that sell batteries) and have them load test your battery. Having the right multimeter is a start but it's in no way a guarantee to be successful. Electrical troubleshooting does require basic electrical knowledge.

 

With a good multimeter, at least you can check the charging system. If you're not comfortable with any of these, taking it to a good garage will be the best solution.

[sprocket]

I just bought a digital meter.  I'll see how that goes.  Stay tuned.

 

R

[Ahsai]

For reference, the battery should measure 12.5 to 12.7v when the car is off.

When the engine is running and maybe with some load such as headlights and a/c, the voltage at the battery should be between 13.5v to 14.5v at all times at any rpm.

[sprocket]

So when the car is off it's measuring 12.77....with engine running it's fluctuating between 15.24 and 15.68.  Then with lights on it's fluctuating from 14.98 and 16.04.  It wouldn't hold a steady number.  Thoughts?

 

R

[Ahsai]

Sounds like a bad regulator to me. Also check out this Pelican article http://www.pelicanparts.com/techarticles/Porsche_944_Turbo/55-ELEC-Voltage_Regulator_Replacement/55-ELEC-Voltage_Regulator_Replacement.htm

 

[Ahsai]

https://www.ecstuning.com/b-bosch-parts/voltage-regulator/92860314200~bos/

[sprocket]

This is for a 951...  is the procedure the same for  944S?  Could I do this myself?  I've changed fuel pressure regulator, coolant tank, speedo gears, dash lights.  I'm no to bad with wrenches...  and the big question is: Is the voltage regulator the real issue?  Or should I do other things before I tear into it?

 

Thanks.

 

R