How to access alternator/VR test points with car running

[travels68]

Hi all,

I'm troubleshooting my 86 Targa not charging (light doesn't come on even with Key in On position and engine off).

Before I dive in to start testing with the Fluke Meter I'd like to know how/where to locate the test points on the Alternator and Voltage Reg while engine is running.

I'm assuming I need to remove the plastic cowling behind the Alternator/Fan assembly but not sure about the order of operations. I don't need to remove the Alternator and then put back on the car to get this thing naked do I?

Thanks!

-kale

[faverymi]

I honestly don't know the right answer but this is what I did after measuring voltages in the car with a meter.

Took me less than 1 hour to have the complete alternator in my hand.

Drove to the rebuild shop. Bench test. ( I think the only way on the 911)

Cost me 150 to have a full rebuild including regulator.

Hopefully good enough for another 30 years.

I think is worth it. My problem was solved.

[sacoffee]

Kale your question leads me to think you should have someone else look at the car .... yes, you have to remove the fan housing and fan to access the alternator. Lots of instructions on the site. You can test voltage at the battery terminals.

[Bob Kontak]

Never trust a word a dentist says.

Hell, he may snuff himself tonight given the pain he deals out to his patients.

However, put your fluke on the battery and see what it is cranking out at idle and report back.

[boyt911sc]

Originally Posted by Bob Kontak

Never trust a word a dentist says.

Hell, he may snuff himself tonight given the pain he deals out to his patients.

However, put your fluke on the battery and see what it is cranking out at idle and report back.

Check your battery voltage first and record it. Then start the engine and let it idle as suggested by BK. The voltage reading during operation will tell you if the atlernator/VR is working properly. No need to access and remove the alternator from the engine.

Check the charge indicator lamp too. The lamp could be busted or burnt. Keep us posted.

Tony

[faverymi]

Originally Posted by Bob Kontak

Never trust a word a dentist says.

Hell, he may snuff himself tonight given the pain he deals out to his patients.

However, put your fluke on the battery and see what it is cranking out at idle and report back.

Naaahhhhh.

Too many Porsches to drive. I'll stick with speeding tickets.

[RWebb]

test the battery thoroughly first - what type is it?

then measure the voltage stopped, at idle, and with the rpm's > 2,000 or so

report back

[theiceman]

im pretty sure that light is used in the excitation circuit. fix the issue of no light with the ignition on first...
i have a feeling if you fix that, all will be good

[Arne2]

Yes, the light is what triggers (excites) the alternator. Having had this issue shortly after buying my car, I'd check the bulb first. Bulb bad = replace it and recheck level of charge. If the bulb is good, something else is wrong. In my case it was a bad VR.

[T77911S]

Originally Posted by theiceman

im pretty sure that light is used in the excitation circuit. fix the issue of no light with the ignition on first...
i have a feeling if you fix that, all will be good

bought time.

fix the bulb. it WILL NOT charge if the bulb is buned out

[Joe Bob]

12.5 at rest
13.0+ at idle
13.5-14.2 at 2500 rpms.

Test at battery terminals. Bulb must light prior to start with ignition at first stop prior to engaging starter. Bulb will go out once proper voltage has been reached, sometimes a rev will do it.

Battery should be fully charged with external source, using the alternator to charge a flat battery is not a good idea.

Bouncing gauges indicate a VR going bad. Best to have the existing alternator to be locally rebuilt as remans generally suck....

[travels68]

Thanks all. I should have included this bit of info before I posted as my diagnostics were well underway before asking about accessing the Alternator.

Here's why I'm fixated on that part of the charging system:

1) Measured voltage at Battery with car at idle and at high RPMs is about 11.8VDC (nothing happening here obviously - no wonder the battery runs down)
2) When battery was at about 7VDC (seriously discharged and wouldn't start) I checked the ignition-on, engine off, Charge light status and it was lit (a bit weak though) so the bulb appears to be good.
3) After charging the battery back up to full charge, with an external plug in unit, the charge light doesn't come on when ignition turned to on, engine off.

My next planned step is to access the alternator to continue testing. I'm inclined to replace the whole thing with brand new high output unit as it sounds like the replacement parts that even good shops get are crap.

Ideas much appreciated!

-Kale

[Joe Bob]

#3.....the bulb coming ON is a self test.

Something is wrong with the charge circuit.

[travels68]

Regarding bad charging circuit does that include alternator or just wiring and or voltage regulator?

Kale

[RWebb]

all - 1st thing, test the bulb

[travels68]

Next step, I'm going to remove the alternator and have it tested. Will let you all know the results.

-Kale

[travels68]

As a followup - I replaced alternator with the Pelican high output unit and now no more worries. While I was at it I took the Fan and cowl to have them powder coated. See pic!