JF-03-SS Posted August 10, 2008 Report Share Posted August 10, 2008 My truck was dead this morning when I went to start it. I have a 15 month old Red top Optima battery, so I don't think that is what it is. So I jumped the battery and my scan gauge is reading 12.9-13.1 volts at idle. What is normal voltage at idle (14.0-14.1)? I am assuming the alternator is no good. What are your thought & opinions before I call the garage? Thanks Jeff~ Quote Link to comment Share on other sites More sharing options...
Rays B4U Posted August 10, 2008 Report Share Posted August 10, 2008 My truck was dead this morning when I went to start it. I have a 15 month old Red top Optima battery, so I don't think that is what it is. So I jumped the battery and my scan gauge is reading 12.9-13.1 volts at idle. What is normal voltage at idle (14.0-14.1)? I am assuming the alternator is no good. What are your thought & opinions before I call the garage? Thanks Jeff~ I'd snatch it off the SS and take it down to your local parts house and have it tested. Also, batteries can go bad prematurely as well, so if your alternator tests good have the battery tested as well. Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted August 10, 2008 Report Share Posted August 10, 2008 If your battery was dead this morning and you jump started it, there is no way the truck would keep running if the alternator wasn't putting out voltage. How dead was the battery, stone cold dead, or just shy of starting(chattering relays)? Like Ray said, have the battery and alternator tested......... Quote Link to comment Share on other sites More sharing options...
JF-03-SS Posted August 10, 2008 Author Report Share Posted August 10, 2008 If your battery was dead this morning and you jump started it, there is no way the truck would keep running if the alternator wasn't putting out voltage. How dead was the battery, stone cold dead, or just shy of starting(chattering relays)? Like Ray said, have the battery and alternator tested......... The remote key locks did not work and when I turned the key, the ONLY thing was the engine light and that was very faint, not even the clock on the radio worked. Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted August 10, 2008 Report Share Posted August 10, 2008 The remote key locks did not work and when I turned the key, the ONLY thing was the engine light and that was very faint, not even the clock on the radio worked. So it was stone cold dead.....after you jump started it and disconnected the cables I assume it ran fine? If so, I think you have a bad battery.......the 12.9-13.1 volts you saw was the battery taking a charge from the alternator. Here's the test, meter the battery with a multimeter with the truck off and running and see what you get. You will see between 13-14.5 volts with the truck running......if you see anything below 12 volts with the truck off, you battery has taken a poo. Quote Link to comment Share on other sites More sharing options...
JF-03-SS Posted August 10, 2008 Author Report Share Posted August 10, 2008 Just had the battery tested and they said the battery was fine and that if the alternator is olny putting out 13 volts it is the alternator that is bad. I will call the Chevy dealer in the AM. So off the change PCMs and see if she will start. Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted August 10, 2008 Report Share Posted August 10, 2008 You don't hear any unusual whining noise from under the hood do you? A lot of times the diodes crap and start to scream, a tell tale sign of a bad alternator......I take it you have an extended warranty? Quote Link to comment Share on other sites More sharing options...
JF-03-SS Posted August 10, 2008 Author Report Share Posted August 10, 2008 You don't hear any unusual whining noise from under the hood do you? A lot of times the diodes crap and start to scream, a tell tale sign of a bad alternator......I take it you have an extended warranty? Long story short Dan........GM gave me a 3 year/36mo. warranty after I owned the truck for 18 months. Quote Link to comment Share on other sites More sharing options...
ss wrecker Posted August 10, 2008 Report Share Posted August 10, 2008 nice thing about the warranty. but hell if you didn't have the alternator is an easy swap took me ten minutes to swap the out the 105 for a 145 and new belt. Quote Link to comment Share on other sites More sharing options...
JF-03-SS Posted August 10, 2008 Author Report Share Posted August 10, 2008 Put the battery back in along w/ stock PCM and everything is fine Also disconnected positive terminal while it was running and it ran fine. Scan gauge showing 13.0-13.4 or so volts from the battery. I am going to let it sit until morning and see what happens. If it is dead again then something must be draining it (but what I would not know) Tick....Tick....Tick.... Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted August 10, 2008 Report Share Posted August 10, 2008 Put the battery back in along w/ stock PCM and everything is fine Also disconnected positive terminal while it was running and it ran fine. Scan gauge showing 13.0-13.4 or so volts from the battery. I am going to let it sit until morning and see what happens. If it is dead again then something must be draining it (but what I would not know) Tick....Tick....Tick.... hmmmmm, if it is dead again tomorrow, time to start checking aftermarket equip. like stereo's etc....... Quote Link to comment Share on other sites More sharing options...
desrtrat Posted August 11, 2008 Report Share Posted August 11, 2008 I'd snatch it off the SS and take it down to your local parts house and have it tested. Also, batteries can go bad prematurely as well, so if your alternator tests good have the battery tested as well. like Ray said. have your alt. bench tested. it will tell you what it is really doing. my guess is a bad diode, and a weak voltage regulator. also bench testing can tell if you have a short in your alt. if your battery is dead again in the morning, if you have a battery charger, put it on a 10-20 amp charge for a while before starting it. you want to have a good charge in your battery so your alt. can do it's thing properly... good luck Quote Link to comment Share on other sites More sharing options...
JF-03-SS Posted August 11, 2008 Author Report Share Posted August 11, 2008 like Ray said. have your alt. bench tested. it will tell you what it is really doing. my guess is a bad diode, and a weak voltage regulator. also bench testing can tell if you have a short in your alt.if your battery is dead again in the morning, if you have a battery charger, put it on a 10-20 amp charge for a while before starting it. you want to have a good charge in your battery so your alt. can do it's thing properly... good luck Truck started right up and now the battery is reading 14.4 volts Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted August 11, 2008 Report Share Posted August 11, 2008 Truck started right up and now the battery is reading 14.4 volts It is possible that you had a loose battery terminal, now that you had it checked and snugged the terminals back up all is fine. Quote Link to comment Share on other sites More sharing options...
KJT13 Posted August 11, 2008 Report Share Posted August 11, 2008 It is possible that you had a loose battery terminal, now that you had it checked and snugged the terminals back up all is fine. that's what I was going to suggest last night, but wanted to hold off until the morning to see what happened when you tried to start it. Quote Link to comment Share on other sites More sharing options...
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