skyak

Hi All,

Wondering what voltage people are seeing from their alternator with the car idling...

My understanding is that over 14.4 volts means the voltage regulator is no longer functioning correctly. Using a voltmeter on the battery I have recently observed a range of voltages on my 07 turbo, all greater than 14.4 volts. The highest voltage (~15 volts) was during a cold snap, and it seems like the colder the temperature the higher the voltage. I have an appointment set up to replace the alternator (apparently on our cars you can not just replace the voltage regulator), but would be interested to hear what voltage others have seen...or if anyone else has seen this issue.

Macster

Not sure where you got that "14.4V" number means the voltage regulator is no longer functioning. I believe the voltage regulator is designed to "fail safe" and not deliver voltage rather than deliver an over voltage which could wreck havoc on the car's electrical system.

Typically the battery voltage will be high after a start, and especially a cold start, in order to recharge the battery. The voltage level at the battery drops over time as the battery gets topped up and the amount of volts routed to the battery is reduced.

Also, if additional electrical load is enabled -- the lights are turned on, the A/C system is turned on -- the battery voltage drops some as some electrical power is instead of being routed to the battery is routed to the car's electrical system to meet the increased electrical demand.

Given the cost of replacing an alternator in one of these cars I'd want to be darn sure it needed replacement.

o7silverturbo

Voltage regulator can fail that you dont get enough voltage or too much.

You can def see 14.8 -14.9 when a/c radio etc is turned on. and snapping the throttle will draw for more amps making your voltage go up.

Has your gauge been moving up and down? battery light?

skyak

The measurements I took were at idle only. I have not had any dash warning lights. It just seems to me that the voltage regulator should never allow over 15 volts if it was working properly...

o7silverturbo

15 volts is alittle on the high side. I can try and take a reading later on my car and see what it is.

also is your battery strong?

Quadcammer

14.1 up to maybe 14.3 at the max.

skyak

Thank you! That is about what I would have expected...makes me feel better about spending the $$ on the replacement.

skyak

Battery is an Interstate, only about a year old. Too much time at 15 volts is probably not good for it though.

Macster

FWIW, I had a new Interstate battery fail in my 996 Turbo after just 7 months.

skyak

Huh...could a bad battery cause a high voltage reading across of it?

o7silverturbo

very unlikely, just sounds like your regulator is on its way out