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Cadillac ATS Technical Discussion Forum Discussion, Voltage varies in Cadillac ATS Discussion Forums; Does anyone know why the voltage tends to dip to around 12.5 volts? I noticed this on both the loaner ...
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    Sir CussFreq is offline Cadillac Owners Member
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    Voltage varies

    Does anyone know why the voltage tends to dip to around 12.5 volts? I noticed this on both the loaner I had while waiting for delivery of my ATS, and in mine. Both are 3.6 Premiums. I see the voltage rise up to over 15V, then I'll look back 10 minutes later and it's around 12.5V. I thought maybe the seat and steering wheel heaters had something to do with it, as I usually have them on, but I've seen it happen several times now when I'm not using them.

    I noticed this because my radar detector shows a constant voltage display, and it appears to be accurate - the voltage always matches what's displayed in the battery voltage information page.

    Doesn't seem to be causing any problems, but it's something to keep it in mind if I ever decide to augment the electronics (add a more powerful sub, etc).

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    Cadillac Cust Svc's Avatar
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    Re: Voltage varies

    Sir CussFreq, I recommend contacting your dealer to see what information their specialized technicians can provide. I would also be happy to look into your voltage concerns further for you if you wish! Please email me with the last eight of your VIN at your convenience. I'm reachable at Katie_Lucille@gmexpert.com.

    Best,

    Katie
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    bungee91 is offline Cadillac Owners Fanatic
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    Re: Voltage varies

    I noticed mine the other day while driving was at 12.5v, however it slowly rose back to the normal 14.4v+
    I didn't notice anything acting abnormal, it was just unexpected.
    I may watch it more often to see if it's common or not (I normally don't have the DIC on battery voltage).

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    Sir CussFreq is offline Cadillac Owners Member
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    Re: Voltage varies

    Quote Originally Posted by bungee91 View Post
    I noticed mine the other day while driving was at 12.5v, however it slowly rose back to the normal 14.4v+
    I didn't notice anything acting abnormal, it was just unexpected.
    I may watch it more often to see if it's common or not (I normally don't have the DIC on battery voltage).
    Yup, that's exactly what it does. I don't typically keep the DIC on voltage either, but the radar detector shows it, so it's always in the corner of my eye. Pretty sure it's normal since it was happening on the loaner as well, but it struck me as odd so I thought I'd ask just to make sure. Typically, a car is supposed to hold 14.4V reliably while on. If I added an aftermarket amp, the varying voltage would actually cause variations in the output of the amp. I think my radar detector actually attempts to use voltage to determine the RPM of the engine as well, to control auto-muting when you're below a configurable threshold. This feature worked fairly well in the STI, but doesn't seem to work at all in the ATS. From the limited testing I did, it seemed like it was always in muted mode while the voltage was down in the 12's. I disabled that feature and haven't done any further testing.

    Katie, I'd be happy to send you my info if you really need it, but if you could try to get an "official answer" on whether or not the variations in voltage while the car is running is normal (and hopefully why this is happening), just generally speaking, it would be greatly appreciated. My ATS is a 3.6 Premium with all the add-ons, the loaner was an ATS 3.6 Premium with everything except the drive assist package, and it sounds like Bungee is seeing the same behavior on a 2.0T, so I don't think it's a one-off with my car. I'll be sure to bring it up next time I'm at the dealer, just to have them check it out. I'm making a list of things to look at once I drop it off for its first service / oil change.

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    This is normal. GM's have been doing this for years. The vehicle is reading the battery voltage and amperage and is adjusting the output of the alternator to manage the charge cycle.

    If your drawing a heavy electrical load, the alternator is set to recharge the battery(14.4v). When the load is not as demanding, or the battery is at a full charge state, the alternator charge circuit is temporarily bypassed(12.5v) to reduce over charging the battery.

    Notice how its either alternator on or alternator off. 14.x vs 12.x and nothing in between.

    No Worries.....my 07 Tahoe did this all the time. It is normal

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    Re: Voltage varies

    Quote Originally Posted by Sir CussFreq View Post
    Katie, I'd be happy to send you my info if you really need it, but if you could try to get an "official answer" on whether or not the variations in voltage while the car is running is normal (and hopefully why this is happening), just generally speaking, it would be greatly appreciated. My ATS is a 3.6 Premium with all the add-ons, the loaner was an ATS 3.6 Premium with everything except the drive assist package, and it sounds like Bungee is seeing the same behavior on a 2.0T, so I don't think it's a one-off with my car. I'll be sure to bring it up next time I'm at the dealer, just to have them check it out. I'm making a list of things to look at once I drop it off for its first service / oil change.
    In order to investigate, my process dictates that I do need the last eight of a VIN; so, I would be happy to check my resources for you if you don't mind sending me a private email with that information. Thanks for your patience, Sir CussFreq!

    Katie
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    Sir CussFreq is offline Cadillac Owners Member
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    Re: Voltage varies

    Quote Originally Posted by ewired View Post
    This is normal. GM's have been doing this for years. The vehicle is reading the battery voltage and amperage and is adjusting the output of the alternator to manage the charge cycle.

    If your drawing a heavy electrical load, the alternator is set to recharge the battery(14.4v). When the load is not as demanding, or the battery is at a full charge state, the alternator charge circuit is temporarily bypassed(12.5v) to reduce over charging the battery.

    Notice how its either alternator on or alternator off. 14.x vs 12.x and nothing in between.

    No Worries.....my 07 Tahoe did this all the time. It is normal
    Perfect, thanks for the info! I was thinking it was probably something along these lines.

    Quote Originally Posted by Cadillac Cust Svc View Post
    In order to investigate, my process dictates that I do need the last eight of a VIN; so, I would be happy to check my resources for you if you don't mind sending me a private email with that information. Thanks for your patience, Sir CussFreq!

    Katie
    Cadillac Customer Service
    OK, thanks anyway then. I'm not real keen on assisting GM with making the correlation between my username and my vehicle... Aside from storing that info in a database, I can't see any other reason why you'd require a VIN for a general inquiry such as this.

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    Re: Voltage varies

    I have the 2.0T for the heck of it I watched mine today and it stayed pretty much at around 14.4 to 14.5 all day.

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    Re: Voltage varies

    Quote Originally Posted by ewired View Post
    This is normal. GM's have been doing this for years. The vehicle is reading the battery voltage and amperage and is adjusting the output of the alternator to manage the charge cycle.
    Notice how its either alternator on or alternator off. 14.x vs 12.x and nothing in between.
    Mine did this again this morning, however in no way does it go from 12.x right back to 14.x.
    I've left the voltage in my DIC and watched it lately on and off, this morning was the first time that it's done it since.
    I started the vehicle and from the initial driving it was at 14.4 and then shortly after going down the road it started falling and was 13.8 - 13.7 - 13.6 -... all the way down to 12.2v.
    It stayed at 12.2v for more than a minute, and then slowly started to climb eventually back to 15v or something around that point.

    This doesn't happen always, so maybe it is programmed this way, however I have my doubts. A battery is for starting a car and that is all, everything afterwards is up to the alternator.

    Also engine RPM seems to have no effect in charging or having the voltage return to normal faster (same reading of 12.2v at 2k rpm and 4k rpm).

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    Re: Voltage varies

    Quote Originally Posted by Sir CussFreq View Post
    OK, thanks anyway then. I'm not real keen on assisting GM with making the correlation between my username and my vehicle... Aside from storing that info in a database, I can't see any other reason why you'd require a VIN for a general inquiry such as this.
    I'm sorry to hear that, SirCussFreq, but I can understand and respect your point of view. Just as a side note, we never use your contact information or forum information to track any aftermarket plans, etc. (I write this because other forum members expressed these concerns earlier, and that is definitely not our intent.)

    Katie
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    Sir CussFreq is offline Cadillac Owners Member
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    Re: Voltage varies

    Quote Originally Posted by Cadillac Cust Svc View Post
    I'm sorry to hear that, SirCussFreq, but I can understand and respect your point of view. Just as a side note, we never use your contact information or forum information to track any aftermarket plans, etc. (I write this because other forum members expressed these concerns earlier, and that is definitely not our intent.)

    Katie
    Cadillac Customer Service
    Thanks for the reassurance, but coming from an auto manufacturer that would not hesitate to attempt to use forum posts as evidence to deny warranty claims, and being in IT security, I have my reservations and prefer to preserve what little privacy the internet can still afford me. If I ever have any issues where the dealership is unable to assist to my satisfaction and I feel some assistance from corporate would be of assistance, I'll be sure to email you. While Customer Service's presence here is odd for the industry, and perhaps at times slightly overbearing, I do feel it shows that you're paying attention to your customers and I applaud the effort.

    I would however feel more comfortable if your policies and processes appeared to respect and help protect internet anonymity rather than erode it.

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    Re: Voltage varies

    Today driving in I watched my voltage and it stayed pretty much as 15.5 volts.

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    bungee91 is offline Cadillac Owners Fanatic
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    Re: Voltage varies

    Mine did the same thing I reported yesterday.
    Dipped to 12.2v and then eventually back up.
    We shall just see if it continues.
    In the morning I do use the heated seat and wheel, however turning both of them off didn't make the voltage rise from 12.2v any quicker with them both on.

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    Re: Voltage varies

    Thread is old, but I might as well add my observations.
    Normally, when driving the voltage (DIC) reads 14.3. However, early this morning as was taking the car to the dealer, voltage was reading in the mid-12's. Driving the loaner (ATS) back home and then to the dealer, its voltage was reading 14.3. Thinking there may be a problem, I called my SA when I got home in my car to ask him about the disparity in voltage readings. He said it was all normal variation. I then did a little Googling on testing a car battery (I have a voltmeter that has been calibrated). According to the article, a battery at rest (at rest overnight) should read between 12.5 and 12.8v, and with the car at idle, the voltage should be between 13.6 and 14.3v.

    My at rest reading was greater than 15v; however, on idle it was now at 14.3v. The high 15+v reading could be due to the fact that he car was just driven, and my information said to run the at rest reading after an overnight of non-use??? But, I was glad to see the idle voltage at 14.3v. I have no idea as to why these variations, but as all seems to be working fine, I'll just hang in there...

    EDIT: Did the at rest reading this morning: 12.3v

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    rsingl is offline Cadillac Owners Fanatic
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    Re: Voltage varies

    My 2008 CTS with the 3.6 has had the same variance since new, as low as 12.5 up to 15.1 volts. As another poster stated it is a programmed function based upon a number of variables including charge state, load, and ambient temperature and is operating as intended. I was curious about this and monitored voltage on a 3.6 ATS I test drove several weeks ago and noticed the same behavior. I plan to order a V Sport version of the CTS and I expect it will have the same varying voltage.

    The 3.6 in the somewhat lighter ATS performs very nicely and it nearly came home with me but I decided to at least take a look at the third generation CTS in person first and I will probably order one in V Sport trim later this year. GM has done some very nice product design in recent years and a C7 Corvette will be my retirement present to myself in a couple of years

    I am glad GM uses real gauges and actual parameter readouts instead of idiot lights masquerading as gauges. Several years ago a friend was riding with me in my 2006 GMC Sierra diesel pickup and told me I had an engine problem because the oil pressure was varying. He had been driving Ford diesel pickups for years and the Ford oil pressure "gauge" simply reads mid-scale whenever there is sufficient pressure unlike the GMC gauge which actually indicates changing pressure as engine speed and oil temperature change. But the Ford approach probably cuts down on customer concerns.

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