Anyone who has a stock alternator in their LS1. What does your amp reading read when you sit with the engine running at idle and no accessories running after a minute? With A/C on? With A/C and radio blaring? Thanks for helping me troubleshoot to anyone able to take a minute to help me with this. My gauge in my 99 T/A has been going just above the mid mark (13v) while the engine is revving (ie:driving, showing off, etc...) maybe to 13.2 or 13.3 or so, then at a stoplight or when at a drive through at idle it will go back down to like 12.6 or so ...and then, depending on how much stuff you have turned on it starts creeping down dangerously close to the yellow striped caution area of the gauge. I'm not used to amperage dropping down that low with the engine running even if it is just idling. But then you revv the enine a couple of seconds and it bounces right back to just a hair over the 13 mark again. Bad alternator maybe? Any advice would be appreciated.

 

I'm not in no way saying our gauges are wonderfully accurate....but...

I just did this: And according to my gauge????

Cold start....shoots right up to 15.5
After one min.....no movement at all
Two minutes....no movement at all
Turned the A/C on MAX, fan on MAX....it dropped about 1 needle width, hardly anything
Turned on the headlights, left the A/C on MAX.....dropped maybe another needle width, hardly at all
Left all that stuff on, cranked my stereo, 1,000 watt amp, 12 inch woof, Matts all around.......dropped maybe another needle width.

Never went below 14.

According to the guage..............and I have a 427ci, hardly stock.

 

I would tell you to pull into any alternator shop and ask them to check everything out, they probably won't charge you much, if anything.

Maybe you just have a jumpy gauge.

 

thanks.. just wondering if it's time for a new alternator... and if so, how much of a pain is it to change them on this car? Anyone else with a stock ls1 that can take a gander at it for me? Don't know of any "alternator shops"... except maybe auto zone... but for that you need to take out the alternator to check it I think

 

Its a 15 minute job to swap them.

You can drive your car to the auto parts store and they will test it all for you.

 

Mine did the exact same thing. I began to look around and found the bolt that the power wire from the battery to the alternator was loose (it would wiggle if you touched it). I opened up the alternator and tightend it down and it has never done that since.

 

Mine now starts at 21.1 & slowly makes it's way back & forth up to 12.7 & to 12.5 with accessories on!
Just put a new alternator on, but I think my battery is on it's way out! won't fully charge and the light never goes back to green even after a charge, gonna replace it this week, but before all that mine never dropped below about 15.

 

Man if you need to replace your alternator or for that matter any electrical parts do not buy them from Auto Zone.

 

I replaced the alternator with a rebuilt one using 130 instead of the factory 103 (? I think ?), and the tensioner pulley, and the belt. No difference... it still likes to stay at 13.1-13.5 while driving, and when at a stoplight will drop down into the yellow around 11.5 or so. I did notice it takes alot longer to drain at a stop if the car is in park as compared with in drive at a light. Maybe its the battery? Anyone?

 

All you can do is go have it checked out. Its either good or bad.

 

I have the same issue, voltmeter in car show below +13, last summer it was steady at 13.5, somewhere between 12-12.5. I took a voltmeter and connected it between + and - on the battery and started figures was pending in between 12.8 to 13.3. I think my battery is not so good any more. I will continue this tomorrow.

 

 

Nut up for an Optima battery. They're not what they used to be but still the best widely available battery you can get. It will save you some headaches.

Alternators: Get you a US built HO unit, Alterstart and Iraggi are the best but there are some good ones on ebay too with shops in California. OEM GM units are very good, they were either 102 or 105 amp rated, depending on the car. Delco replacements are OK. Napa parts are marginal, Vatozone and OReilly's alternators SUCK. Seriously, grab you a US built reman and be happy.

Your gauge is a volt gauge, only moderately helpful and relatively accurate. It's really an indicator at best. Amp output is more important and needs to be checked under load. Typical amp output at 800rpm idle is 45-55 IIRC. You'll get max output at 2000rpm. That needle jump is common, especially for marginal quality units. The AC compressor and fan blowers are big draws and hit at once when they come on. If your AC comp is going out or old, the bearings may be wearing, which will enhance the hit you see on your gauge. Upgrade your Big 3 to 4ga, 2-0 if you have stereo, and that will help a lot. Big 3 = battery neg to chassis, battery pos to alternator, engine to chassis ground.