Have a 01 Tahoe with new red top and fairly new alternator. It charges at about 14v. But if I leave the Tahoe set for a week, it wont start.Where do I look for a voltage leak. The Tahoe seems to be working fine, nothing staying on. Where do I start.

Put a multimeter across the battery and measure the voltage.. hopefully you get around 12.5V give or take..
Start the engine and check again, this time you are looking for around 14.2 - 14.6v
If you get less than 14v even if you rev it to 2000 rpm, then the alternator could be on it's way out.
If all is fine, you need to measure the dark current.. this is what is being drawn from the battery when not in use.
Remove one battery lead, and connect the multimeter set to amps between the lead and battery,, do not turn anything on. the reading should be maybe 25mA at the most.. anything much higher, and you have a drain somewhere.. could be the alternator rectifier breaking down, or a partial short.

You have it set on automatic or manual .. If it is set for automatic the charger will cycle on and off so the battery does not charge too much. If it is manual when battery reaches charged voltage, it is time to disconnect.

Start at the battery and check with a dc volt meter while it is running. A good battery puts out a max of 12.5 volts.... If you have ATLEAST 13.0 volts then your alternator is working, but not at peak efficiency which is more like 14.0 volts. If you detect that it isn't charging the next step is to attach the volt meter directly to the alternator. There should be a "hot wire(s)" meaning it should have a rubber boot over it and usually is red like the wires running to the positive side of the battery. NOT running it should show the same voltage as the battery, with the vehicle running it should be producing above 12.5 volts more like 14 volts. If you DO have that type of voltage (14v) there and not at the battery while it's running then yes the alternator is good and the wiring between the alternator and battery is bad/shorted. Don't be MISLEAD because alternators that are going bad have a tendency to work intermittent. If this is the case don't chance it, REPLACE it

at alternator gig wire battery voltage,one wire battery volts one less . battery volts wire goes to automatic shut down relay, less then battery voltage wire to pcm fuse will be 20 amp just ck all that size.

Altenator is bust or the belt to the altenator is broken.

It sounds that you have a problem with your car alternator charging system: it should be indicated by a charging warning red light being permanently on.
If you have a multimeter, you can check the voltage at your battery terminal:
- with motor off, the voltage should read around 12.8V with anything under 11 v indicating a 'shorted' bad battery.
- with motor running, the voltage at the battery terminal should be around 13.8V with any reading above or below that indicating that your car alternator or regulator is faulty.
ps. I am really surprised that you needed to get 3 replacement (new) car batteries: this can only be caused if you are actually 'cooking' them: this would be caused by your alternator regulator allowing a high (over 14V) voltage and thus 'boiling' the electrolyte away and damaging the battery plates!

If you have a fully charged battery when you installed then 14 volts is way to much charge for the battery which would mean that the alternator probably has a faulty regulator and the alternator needs to be changed otherwise you will continue to install new batteries. If the battery was in an uncharged state then it is possible for the alternator to charge at full capacity to charge up the battery.

check the charging from alternator if ok you might have a blown fuse ect if no charging 14v id say alternator brushes . or regulator in the alternator

Take a voltmeter with the car off and measure the voltage, should be around 12V. With the car running, measure again and this time it should read 13V-14V. If it does read 13V-14V then it means that the alternator is working. If it is below 12V, then it means your alternator is not charging the battery. If it's above 14V, then it means your alternator is overcharging and damaging the battery.

Ck the charge rate at the battery posts. The proper range is 23.6 to 14.2v , The higher the voltage the llower the amps. Ie; at 13v Alternator is about 10% under capacity. @ 12v it is charging at max capacity. @ 15 v isthe alt is not charging but frying your battery. 9amps is ok if battery is fairly charged but at start up it should sit on 13-13.6 volts. for about 15 seconds the start climbing to less charge towards 14.2.