mkubacak

On my 2006 today, I had the check gauges light come on and the Voltmeter was reading just over 11. I get home and check it with the multimeter and it says 11.3 while running and 11.4 when off. I took the alternator off and went to three different mcparts stores and two tested good and one tested fail.

I will preface this with stating that I am an idiot when it comes to how anything electrical works. But, is there something else that would cause this or should I just put a new alternator on? If you do have an idea of something to check, please dumb it down as much as possible.

Thanks in advance for any and all help.

rockcrawler304

You say 11.3 when running and 11.4 when off. Are you just checking across the battery posts? If so did you at least check BOTH batteries?

What was it reading when you had it tested? When the place that it failed at said it failed, did they say what failed?

mkubacak

Yes that was both batteries. I was not sure where else to check. I guess I should have checked the alternator, but I was unsure as exactly where to put the leads to get the test right.

I watched them check the alternator at all three places and their machines only registered a pass or fail. I guess I should have asked if it gave more detailed information.

rockcrawler304

It has been several years since I had a place check an alt for me so I guess the "New" machines need to be idiot (employee) proof and just say pass / fail

You need to know the actual alt output. Should be about 13.5 to 14 volts. The easiest way is not the most accurate way but pretty close, is to just put the leads from your volt meter on the battery posts while it is running. Sounds like this is how you did it but I'm just making sure. Depending on the volt meter you should have a setting of 20vDC. Use this. You should get a pretty close reading. Do this on both batteries. If this IS how you did it you most likely have a bad alt but if I remember correctly the voltage output is regulated by the ECM. If I'm not an idiot and this is correct you may have a different problem. Hopefully someone else will chime in on this.

jeephauler

I had my check gauges light come on a few different times sporadically and then it finally came on and stayed on when my passenger battery blew up. Make sure both of your batteries are good, clean all battery connections, and inspect your cross over cable for any corrosion or damage.

If your on the original batteries still like I was, replace them now as they are due, you dont want the mess that I had of a battery blowing up. If replacing them fixes your problem, great, if not no big deal because they should be replaced anyhow.

surfram

Loose/rusted positive battery cable from the passenger side battery to the driver's side battery. The truck's computer regulates the charging voltage and freaks out when it detects a bad connection to the driver's side battery. Passenger side battery gets fried at 18 volts followed by check guages and low voltage.