Is it squealing on gas? Do you see any catching or skipping? If not, leave it alone.

 

Generally it is better to be undertensioned than overtensioned (so as not to stress bearings) but those numbers are indeed quite low. If you are confident in your readings then I would personally

1. Ask the shop who replaced the belts to have another look
2. Buy a selection of shims for the fan and alternator belt from Porsche (inexpensive)
3. Learn to do the belts myself for the next go-around (not difficult)

You know what they say —- if you want a job done right, do it yourself! 👍

 

Great advice from you as always, Jlaa. Thanks.

 

Well, you can add me to this thread - I started her up this morning and the ABS light flickered on and off several times - idle is weird (jumpy oil pressure gauge) and I have some dash lights flickering which tells me the power isn't steady state. I have an OBDII monitor plugged in and I was getting anywhere between 12V and 15.8V while driving, all over the place.

It's either the voltage regulator or the alternator. We'll see.

 

.... or you have a grounding problem. Check the obvious ground points, and is your main battery earth strip/cable the original?

 

Will take a look and clean the battery posts at a minimum. The earth cable is original as far as I know. The car has 106,000 miles on it and it's a 1996, so anything is possible. I'll also note the car was fine for a 150 mile drive the other day and this started happening after I gave it a wash.

 

First, cheapest thing to do is replace the earth strap. Future-proofing for a few dollars.

But yes in your case I'd also check under the seats/carpets for any water.

 

^^This
you say you bought new alternator & ground cables. Did you clean the crimp ring so they’re shiny and the same for the chassis ground point? Just 100 milliohms will drop volts at the charging currents.
you also want to check the ones in the frunk. You should be able to get 13.9V with good connections at 2000 rpm

 

When a problem like this suddenly appears, it's always good to review "what changed" since the car was last working.

 

"anywhere between 12V and 15.8V while driving" - Are these numbers measured by a voltmeter directly connected to the battery terminals? If yes, then 15.8v is way too high, potentially pointing to the voltage regulator problem.

 

No, it's measured from the ODBII port with a ScanGauge.

 

Measure with a DVM at the battery if you can. If you have some electrical issue, the ECU may not be able to measure and report battery voltage accurately.

 

Update: Convinced water got into the electrical system somewhere. Battery was off tender, 12.5V. Car started up completely fine. Alternator output 14V flat. Voltage at battery and ECU was 14V flat. Loaded up the car with A/C, lights, interior lights, dropped to 13.8V, normal. The ground strap is pretty tarnished though, new one on the way.

 

Good news.

Take out the front mat(s) - see if you can get your hand under the sound deadening/foam - looking for moisture.

 

Thank you @IXLR8 .

I tried Bud Potting Box PB-1558 and a generic 0.56" voltmeter (instead of the Datel). The benefit of the generic was that it matches my car's interior lighting. However, it didn't quite allow the ashtray to open all the way.

https://www.ebay.com/itm/225042006193






So then I used BUD potting box PB-1579 and a generic 0.36" voltmeter ------ it looked great but my velcro just would not stick to my carpet.
So I put the meter INSIDE the ashtray. Thanks @IXLR8 ! It was a satisfying project to allow me to keep an eye on the voltage at the battery terminals.
BTW This draws 10mA, so I don't have it on all the time. I used an SAE connector - so when I unplug my battery tender, I plug in the voltmeter (with the SAE connector). After parking the car in the garage, I unplug the voltmeter and plug in the battery tender (with SAE connector).