Draining Battery? Need some help.

Hi-

before I get my meter out and go crazy, maybe someone has had this problem before:

91 Cherokee Laredo

Starting has been slower and slower over the last week.
Noticed that alt has trouble keeping up with power demand when running lights/heater fan/wipers/stereo
all at the same time.

Planned on doing the 136A alt swap as found here on the forums. Got the alt, but before I put it in I decided to get a new battery and cables.

Put new batt and cables in last night, started Chero 3x to check batt and cables- all worked fine, volt meter looked fine.

This morning, voltmeter at like 10V, all acc seem to be working fine, but no starting at all. Odd thing is batt measures 12V right at battery.

I'm more used to the old school set up where the alt is internally regulated, connections are pretty much alt to batt, and batt to starter relay.

First question:
is there a common component that goes bad which drains the battery in this set up?

Where does the output wire from the alt go to?

As an upgrade, I used 2 GA batt cables and a marine connectors- one short cable to the fuse box, and one to the starter. Ground was hooked to side of block as factory.

Stumped as to why the batt measures 12 at batt, but 10 on meter in dash.

I'd like some suggestions, or at least a link for a schematic...? I have ordered a factory electrical supplement, but it's not here yet before someone says to get one.

Thanks Much

xj_convert

First off, that alt gauge is CRAP!Not because its bad, but because they are not very accurate.
I had the same thing happen to me and while searching for a fix i came across a wiring upgrade for the acc. circuit.It helped some, but the gauge is still off.
Last week i had a 2002 expedition in the shop with a similar problem as yours.
I dissconnected the batt neg. terminal and put a test light inline.
I started pulling fuses till the light went out.
Turns out that the diode trio inside the alt had taken a crap.I verified this by testing the alt for A.C. voltage while charging.
I have also seen stupid stuff like napkins get hung in the glove box switch and leave the light on all night.
Good luck.

yeah, I realize the voltmeter is crap, but it's accurate enough (verified with digital meter)

I'm wondering if my alt is not also bad, and allowing leakage back through it.

Where does the alt output go on the XJs?
I know, ultimately back to the battery, but I mean physically where does the wire connect to after the alt?

Thanks

B

starter relay, right hand shock tower Blue wire

Re: Draining Battery? Need some help. SOLVED

Diagnosed my problem by jumping 12V directly to starter switch terminal on starter (not the main heavy 12V supply).

Starter spun faster than it has since I bought the xj.
Traced factory wire back to the bane of my electrical existence:
a butt splice connector that had corroded enough to pass less than 12V
but was passing some voltage. This is why I always make splices using GM Weather Pak connectors.

The odd thing however is that older staters (like FSJs for one)
will spin fast if the heavy supply is OK, but if the key 12V is weak, it may or may not kick in the relay (or solenoid if you like).

Never saw it that the starter was slow over the key voltage.

Now I know that this is a seperate issue from the alternator not keeping up in bad weather with all of the acc running (wipers/heat/defrost/stereo/lights) all going at once. That will be fixed with the 136A alt upgrade later this week.

Thanks guys

xj_convert