check gauge light came on... jeep died

[Lulu]

Hey guys and gals. Did a search but no info came back that matched.
I just sold my old 99 Jeep Cherokee Sport 4.0 L to a friend of mine and the first day he drove it, it was about 30 degrees and the check gauge light came on, batt gauge dropped and it died. NOT the check engine light as this vehicle has both. Take battery to autozone zone and it is drained but cells are fine. Takes charge and we get the car home. Pull alternator and take it to autozone for bench test and it passed. Pulled out all relays and fuses and put them back. When we put everything back together the light was out and the gauge was at 14 where it stayed for 3 weeks of warmer weather. Now yesterday at about 30 degrees again same thing happens. Light comes on gauge begins to drop. Didn't give it a chance to die. It's in garage waiting on some bright ideas. Cables look fine, plugs look clean and tight on PCM (have read stories of that being problem).

Any ideas from MUD?
thanks and sorry for long post wanted to give as much info as possible

 

[Mace]

gotta be connections or wires somewhere.

How long does it take to drain the battery?

If it takes a while to drain the battery, then the cables are good to the battery. Could be the alt wires.

If the light comes on and the battery drains almost immedately, then it sounds like the battery cables are not getting a good connection somehow..

 

[Lulu]

Thanks for input Mace. Was driven over an hour before died last time. Not an hour straight, over several short trips. Never hesitated when starting. Put everything back together this morning again, drove it for 15 minutes continuous with no light on, but battery gauge was sitting on about 11 or just below. We are thinking connections too but are not sure which it could be. One of the pcm plugs had dirt in some of the holes but they looked like they were inactive holes, no metal sleeve in them. Plugged all three back in, felt very snug. Now as mentioned above, no check gauge light but gauge is pointing at 11v and less.
oh yea, scanner at autozone showed no codes.

 

[Mace]

Just cause the plastic snap is holding strong does not mean the metal contacts are doing well..

Start messing around with the alternator wires (be careful)

I bet you are not exciting the alternator..

 

[Lulu]

Is that something I can check with volt/ohm meter? What would I check and what exactly does that (exciting the alternator) mean?

thx again