Boy do I need the Brain Trust about now... Wrench question

[pwd72s]

This one seems to be a hellofa bang for the buck. A multimeter pretty much a necessity for hunting down a parasitic draw.

https://www.amazon.com/gp/product/B071JL6LLL?SubscriptionId=AKIAIBX4MGJBG42TO3NQ&tag=chtrbr10607-20&asc_source=referral&asc_campaign=471&asc_refurl=https%3A%2F%2Fbestreviews.com%2Freviews %2Fbest-multimeters&th=1

[1990C4S]

There is absolutely nothing wrong with these (below) for automotive work. I own a LOT of meters, at least six Flukes, a Simpson somewhere, etc. This HF is my go-to 90% of the time.

It works fine, if I drop it or drive over it, I don't care...

https://www.harborfreight.com/7-function-digital-multimeter-63759.html

Back on track, I think the TPS issue is 100% not related...

[pwd72s]

But then, the Lake Oswego HOA only allows... (Oregon Joke)

https://www.amazon.com/Fluke-KIT-Automotive-Multimeter-Combo/dp/B005T5G38E/ref=asc_df_B005T5G38E?tag=bingshoppinga-20&linkCode=df0&hvadid=80607997949498&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4584207578851943&psc=1

[LWJ]

Gents,

I own at least 4 DMM's. Nothing with a brand name on it. (Miss my analog MultiMeter but that is a different story!)

Fanaudical may have been onto something waaaay back in the thread.

Daughter has the car for the last few days. I had her measure 10 minutes after opening up the doors / hood so that the car goes back to sleep.

She reports 12.41 yesterday. I am concerned. Not a lot of wiggle room with that number.

I have her come over and I measure as it is running to see the alternator charge voltage. I got 12.1 or 12.2 for a second and then it jumped to a healthy 14.4 or so.

Resting voltage was 12.7.

So I think that perhaps when Fanaudical suggested a failing bridge rectifier, he may have been accurate. Google doesn't give much info on this defect. Any of you big brains know more?

Thank you all! This is a challenge. We may be getting closer!

[sc_rufctr]

Yep, If all else fails replace the alternator.

[unclebilly]

Does the car have aftermarket LED tail lights in it? Our older cayenne goes crazy when our trailers are connected to it.

Does she sometimes park it with a signal light left on? This will cause the park lights to illuminate.

[1990C4S]

Originally Posted by LWJ

I have her come over and I measure as it is running to see the alternator charge voltage. I got 12.1 or 12.2 for a second and then it jumped to a healthy 14.4 or so.

Resting voltage was 12.7.

So I think that perhaps when Fanaudical suggested a failing bridge rectifier, he may have been accurate. Google doesn't give much info on this defect. Any of you big brains know more?

Thank you all! This is a challenge. We may be getting closer!

On 'some' cars the alternators shut off until the battery voltage drops to a set voltage, but it does not appear your TDI has that 'feature. Is the serpentine belt good and the pulleys/tensioner?

It's also possible that your alternator is failing/intermittent. I'm guessing it's the second one.

Also, make sure the large wires from the alternator are clean and secure around your fuse box/battery. These connections were common failure points on the older TDI's.

I think I would buy a new alternator at this point.

There's still a discrepancy between the discharge condition and the lack of parasitic current, unless you are downstream of the alternator when you're testing.

[908/930]

Looks like it is not fixed yet so here is my guess, I think you could have a standard relay that is sticking on. Sounds like you have been measuring current draw after car is turned off and it is inconsistent?

If the car keeps running once started so I do not think it is the alternator. I remember reading someone here had a problem with carbon build up in the starter solenoid that would drain the battery, long shot but worth checking. I have seen a glovebox light switch act up intermittently, could pull the bulbs or fuses to verify.

EDIT Reading your post again you said when turned off the current draw went from 2A to 0.0A was that main body module turning off? With a 70AH batt you are looking for about 2A to drain it in 24hrs.

[911 Rod]

Alarm?

[Bob Kontak]

Originally Posted by 911 Rod

Alarm?

I have seen parasitic draw when the alarm batteries die. Pull the security fuse, the draw is gone.

[LWJ]

Here is where I am now.

Daughter has been driving and reporting voltage 1-2 times per day.

AND...she reports the battery light is coming on intermittently.

I never saw a battery light. I never saw any amperage leakage outside of 0.01.

Best guess is gradual failure of alternator. Not a bad guess. I hope it is the right one.

[908/930]

How many miles on the car? Yes if the alternator brushes are almost gone it can work intermittently, won't last long at that stage.

[scottmandue]

You could go all Hunter S Thompson on the car and pull your 44. 😉

[1990C4S]

https://www.amazon.com/Palumma-Charger-Adapter-Display-Battery/dp/B0773BYS6P/ref=sxin_17_pa_sp_search_thematic_sspa?content-id=amzn1.sym.fc48733d-66f8-4b9b-aacf-cfa5b264e791%3Aamzn1.sym.fc48733d-66f8-4b9b-aacf-cfa5b264e791&crid=3DWE6Z1IK1DOH&cv_ct_cx=cigarette+voltmeter+12v&keywords=cigarette+voltmeter+12v&pd_rd_i=B0773BYS6P&pd_rd_r=a34dd23f-5eac-42ee-844d-24cfed3fc262&pd_rd_w=Pz90D&pd_rd_wg=xdoic&pf_rd_p=fc48733d-66f8-4b9b-aacf-cfa5b264e791&pf_rd_r=692KMF2RFHSA8T190XSN&qid=1697752009&sbo=RZvfv%2F%2FHxDF%2BO5021pAnSA%3D%3D&sprefix=cigarette+voltmeter%2Caps%2C209&sr=1-2-2b34d040-5c83-4b7f-ba01-15975dfb8828-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9zZWFyY2hfdGhlbWF0aWM&psc=1

No need to guess. Find out the running voltage when the light comes on.

[john70t]

Originally Posted by LWJ

AND...she reports the battery light is coming on intermittently.

I'm also gonna guess the alternator...as several here already have.

Double-check the battery connections and eng/trans ground straps are tight and clean first, but while running it shouldn't need any battery at all.
(Battery cables can also corrode behind the sleeve so it's good to use a grease on them after installation)

[908/930]

A bad alternator does not explain battery going dead overnight.

[fanaudical]

A flaky diode bridge in the alternator might explain all this...

[LWJ]

^^*yes. At mechanic #3 now.

[john70t]

Someone called it early in this thread

https://vehiclefreak.com/bad-alternator-diode-symptoms-causes-and-how-to-test/
One of the main lousy alternator diode symptoms is a battery that drains overnight, essentially mimicking a parasitic drain. Other less common symptoms include stalling or battery drainage while driving, battery warning light, and dim lights

Accidentally reversing the positive and negative terminals when installing a battery is almost guaranteed to burn the alternator diode. By doing so, you are sending the battery current to the diode in essentially the wrong direction.

[908/930]

Hopefully #3 figures it out. The one thing making me think it is not a bad diode is when the current draw was checked with car off it was very low, pretty sure when transistors or diodes fail they blow up or lock on, no longer a semiconductor just a conductor, not intermittent. Alternator would be a nice easy fix if it is that.