Ck986

I have a year old battery and typically if I'm driving a charged battery it will read 13.8 and drop over time to 13 or 13.2. If I run the air conditioner the voltage drops to 12.8 or slightly higher. As soon as I shut off the ac the voltage goes back up to 13+. I use to keep the battery on the trickle charger all week and drive the car on the weekends, but now I drive it daily to work as I no longer commute into the city. I'll likely continue driving it daily until the fall when I'll lease a work car. I am enjoying driving the TT daily.

I just wanted to know if this is typical or should the voltage stay at 13.5-13.8 at all times. I have a new belt and all new idler rollers and my ac pulley is fine.

Macster

Pretty much the manner in which my Turbo's volt meter reads.

Been doing this for as long as I can remember.

In fact I got a bit spooked on my first road trip with the car shortly after I bought it. I happened to be somewhere in NV on I-80, in a town for gas when I got a call from the SM at the dealer informing me my other car was ready to pick up. I told the SM I would be there in a week to pick up the car.

As I was on the phone I noticed the volt meter gage reading what I thought was low. I asked the SM and he got one of the senior techs on the phone who after I described the reading told me everything was ok.

The voltage reading is what the battery is getting. Initially after a start it requires topping up so it receives around 13.5V to nearly 14V. But this drops off after some minutes of driving.

If you flip on the lights, or turn on the A/C, the level drops as some voltage is routed away from the battery to supply the other electrical loads now requiring electrical power.

Ck986

Thanks, I drove 120 miles today in 95 degree weather with the AC on and the car drove great. The voltage fluctuated between 12.7 - 13. RPm's didn't appear to matter so long as I was not idling. As soon as I got back to the office I turned the AC off and the voltage jumped back to 13.2-13.5.

993GT

I did a new V.R. last year, never goes below ~13.5V now
Starts at 14V

mcbit

I've recently sorted out the low voltage issues on mine, the major one being a faulty new original earth strap. Currently in 115F+ temps: it starts at 14.1V when warmed up and cruising it is constantly at 13.7V at idle with heavy AC load and fans running it drops to about 13.2V.

Ck986

So it sounds like, my VR may not be working at full capacity but still holding its own. I guess ill keep it on my radar to possibly change it out in a year or two if it lasts that long.

Macster

Well, I have to point out the car's in-dash voltage gage may not be the best measuring device to rely upon. It is probably like the coolant temp gage more there for show than go.

If you suspect the VR is not working properly you should consider having the charging system checked out which will use better measuring tools/equipment to measure the voltage and current involved.

You might also come away with a better sense of how your car's gage reads vs. actual numbers so you can rely upon the gage with more confidence.

Ck986

I have a multi meter and will likely test it soon, but have no real concerns as I am not experiencing any problems. I was just asking to see if what I was experiencing was normal or not. Sounds like it is for a 12 year old alternator.

mcbit

I'm sure there are variations vehicle to vehicle but my dash voltmeter gives a pretty fair representation of reality.