When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
mine sits at around 12.8 at idle with the ac on. Sometimes gets to 12.5 and going down the road it’s 13-13.2. My new truck does the same thing so I haven’t worried with it.
Should be higher. On the new truck there's variables there that can come into play.
Y'all may have seen my 10 year old, 50 page long alternator thread here on LS1tech. I've been through it with alternators I'm not just throwing things out there.
All of my vehicles and my customer vehicles with quality alternators, or after straightening out charging issues maintain around 14 at idle. There are a few here and there that will sit at 13.3 or so with questionable alternators, and every once in a while its just the way it is, but it should never be anywhere in the 12's or very close to 12's. You have to be careful with some of the newer cars, sometimes they will ramp the charging down if it isn't needed and you'll see lower charge levels but they will do that even at high way speeds and only momentarily. If you have a vehicle that is always in the 12-13 range at idle there's a reason for it that can be corrected.
F body cars/ls cars/trucks etc can and will maintain right around 14 volts at idle even with a/c and headlights on when all things are correct. My 2000 camaro did, my 2004 sierra did, my customer cars do, the alt's I have done on F bodies for other people do. Y'all have a problem if you're going that low, and it can be fixed I promise ya.
Last edited by 00pooterSS; 10-11-2019 at 12:57 PM.
None of that will cause the alternator to stop charging at idle or drop down to.. what did you say it was, 12.8 or so? It should maintain near 14 at idle. Unless you're saying the idle is dropping down so low the alternator stops charging but that would be like I dunno.. 400 ish rpm
Yes, the AC pressure switch isn't calling the clutch to engage at times. Then when it does, 40% of the time it causes the engine to stall at least that is what I'm thinking.
It did it one time, engaged, I felt the AC blowing super cold and the engine almost stalled but I gave it some throttle keeping it running and drove a few blocks, noticing that it wanted to die after each gear change.
When I came to a stop and let it idle with no throttle, it died. Could be a combination of a few things.
As far as the ALT charging, I'm thinking I saw the voltage drop because the engine was in the process of stalling. I haven't had the car stall with the AC not on.
Should be higher. On the new truck there's variables there that can come into play.
Y'all may have seen my 10 year old, 50 page long alternator thread here on LS1tech. I've been through it with alternators I'm not just throwing things out there.
All of my vehicles and my customer vehicles with quality alternators, or after straightening out charging issues maintain around 14 at idle. There are a few here and there that will sit at 13.3 or so with questionable alternators, and every once in a while its just the way it is, but it should never be anywhere in the 12's or very close to 12's. You have to be careful with some of the newer cars, sometimes they will ramp the charging down if it isn't needed and you'll see lower charge levels but they will do that even at high way speeds and only momentarily. If you have a vehicle that is always in the 12-13 range at idle there's a reason for it that can be corrected.
F body cars/ls cars/trucks etc can and will maintain right around 14 volts at idle even with a/c and headlights on when all things are correct. My 2000 camaro did, my 2004 sierra did, my customer cars do, the alt's I have done on F bodies for other people do. Y'all have a problem if you're going that low, and it can be fixed I promise ya.
I am definitely looking into my charging system after the next round of mods to the engine.
Gotcha. Watch it at normal idle speed of 600-800 or whatever you have. Preferably should be over 13
A/C idle often has to be learned by the computer too. I go through this a lot as a tech and have to start cars and let them idle for a good 10 or so minutes with the a/c on so the computer learns idle parameters with the a/c on. If I just fire one up and drive it without letting it learn it'll stall a lot and idle low. This happens mostly after battery replacement/getting disconnected, or a battery going dead in which the computer loses the learn.
Dig through my alternator thread a little if you get some time. The short of it is I had charging problems from 10 alternators in a row over about a years time, little under. All of them were brand new. Ended up grabbing a OEM alternator off a truck at a junk yard and never had a problem again. Neither did the next owner of that car or the owner after that. After that I started recommending people put the higher output 145 amp truck alternator on their F body cars and the thread is 50 pages long of people saying their charging issues they couldn't figure out are now fixed after doing that alternator. For some reason all the replacement F body alternators are absolute ****.
Gotcha. Watch it at normal idle speed of 600-800 or whatever you have. Preferably should be over 13
A/C idle often has to be learned by the computer too. I go through this a lot as a tech and have to start cars and let them idle for a good 10 or so minutes with the a/c on so the computer learns idle parameters with the a/c on. If I just fire one up and drive it without letting it learn it'll stall a lot and idle low. This happens mostly after battery replacement/getting disconnected, or a battery going dead in which the computer loses the learn.
Dig through my alternator thread a little if you get some time. The short of it is I had charging problems from 10 alternators in a row over about a years time, little under. All of them were brand new. Ended up grabbing a OEM alternator off a truck at a junk yard and never had a problem again. Neither did the next owner of that car or the owner after that. After that I started recommending people put the higher output 145 amp truck alternator on their F body cars and the thread is 50 pages long of people saying their charging issues they couldn't figure out are now fixed after doing that alternator. For some reason all the replacement F body alternators are absolute ****.
I'll check it out. I have an AC delco truck 145 amp ALT on mine.
I'll check it out. I have an AC delco truck 145 amp ALT on mine.
Well hell that should do it. But I did have a lot of issues with non OEM alternators so it could be the alternator itself. Do you have underdrive pulleys on it by chance?
Well hell that should do it. But I did have a lot of issues with non OEM alternators so it could be the alternator itself. Do you have underdrive pulleys on it by chance?
I did have an UDP on it. I installed a stock one back on and saw no difference. I didn't have any issues prior until I installed the AC system back on the car.
Get you a good quality OE alternator or a aftermarket high end one and you should be good. Mine would work fine on start up but as the engine warmed up and underhood temps got higher the voltage would drop and drop. They would test the alternators and of course they showed good because it was cold (well room temp) mine would go to **** after warm up.
Glad you mentioned this. My aftermarket 145 was doing the same thing. Just went and got a OE one from the junkyard.
Glad you mentioned this. My aftermarket 145 was doing the same thing. Just went and got a OE one from the junkyard.
And that junkyard OE alternator fixed all your problems, didn't it?
That's why I made the alternator thread and told everyone to go get one from the junk yard. I bought 10 in a row, trying multiple brands and types (rebuilt/new/premium/) from different suppliers and they were ALL junk. I suspected something on the car was the issue or something on it with every alternator I got. I really thought it was something causing it and tested everything multiple times like, wiring, amp draw from several circuits, ohmed out connections and wiring all over etc etc..
But I never ever had a problem until I went away from having an OEM alternator and put a "new" one on it. That's when my charging issues started. And the only thing that fixed all the issues was putting another OEM back on it. And I had to go to a f'ing junkyard to get a quality alternator. Well I didn't HAVE to but I was scared to pay $500 to the dealership parts house and it possibly fail and have them tell me "sorry we can't warranty it cause the car is modded". So I knew I needed to try an OEM alternator and I wanted a cheap test to prove my theory. I tried it and it worked. That car would charge 14 volts at idle with a/c on, headlights on, stereo system with amp at full blast, windshield wipers turned on etc.. So the junkyard alternator thread was born..
It should charge at idle, charging only above idle is not okay. It should full charge at idle on a 100 degree day with the head lights ac and radio on too. The original did... But we forget to hold them to that standard. You should be able to get an alternator that will do what the original one did, and it's damn near impossible to get that with a off the shelf alternator.
Rant over. Sorry for derailing the thread and getting on a soap box.
Last edited by 00pooterSS; 10-14-2019 at 03:01 PM.
Glad you mentioned this. My aftermarket 145 was doing the same thing. Just went and got a OE one from the junkyard.
People really really really want to believe that if the alternator charges at some times and not others that it's something else causing it. I've noticed that 100 times through all this alternator crap I've gone through and with my alternator thread, and in my career. We are all wired to think "if it's new it must be good" and if there's an issue "it can't be the new part, it's new". That train of thought could not be further from the truth. I've been a tech over 20 years, out of the box **** parts have taught me too many times that just because they are new does not guarantee they are good.
It should charge at idle, charging only above idle is not okay. It should full charge at idle on a 100 degree day with the head lights ac and radio on too. The original did... But we forget to hold them to that standard. You should be able to get an alternator that will do what the original one did, and it's damn near impossible to get that with a off the shelf alternator.
That's why I made the alternator thread and told everyone to go get one from the junk yard.
Anyway, that junk yard alternator solved all your problems, didn't it?
Rant over. Sorry for derailing the thread and getting on a soap box.
Well guys, got caught in a down pour heading to a car show and lost control of the car. Ended up hit a curb head on with the right front wheel, bending my tubular k-member, LCA, UCA, wheel, tierod end. I believe I was very lucky not to total the car.
So I'm dropping the engine out to change my top end setup and cam while I assess the k-member damage.
I bought a pair of LS3 821's and a stock intake to run. Last night I disassembled one of the heads.
I plan to port the heads and possibly the intake and swap in the new cam. I sold the old cathedral port set up.
Well guys, got caught in a down pour heading to a car show and lost control of the car. Ended up hit a curb head on with the right front wheel, bending my tubular k-member, LCA, UCA, wheel, tierod end. I believe I was very lucky not to total the car.
So I'm dropping the engine out to change my top end setup and cam while I assess the k-member damage.
I bought a pair of LS3 821's and a stock intake to run. Last night I disassembled one of the heads.
I plan to port the heads and possibly the intake and swap in the new cam. I sold the old cathedral port set up.
Thanks guys, it's all good. Looking forward to seeing if I gain any horse power with this new top end setup. Brand new LS3 intake bought from a fellow member. A "before" shot on the intake port. Had to replace a few valves, the engine these heads came off of broke some piston rings. Disassembled to start porting.
821 heads I picked up from a buddy. Came off of a boosted 5th gen. Had three pistons break rings and bent a few valves. A little pre porting. Valves out, head cleaned. Gasket matching, seeing how much I can open the exhaust ports. 2" primaries are nice. Rough cutting.
10-11-2019, 12:48 PM
