2011 Liberty battery drain, reduced power and AC, no cruise control, not battery, alternator, or PCM.

[pinhotihiker]

Hello. I'm at my wits end here and looking for help. 2011 Liberty popped the "battery light" indicating charging issues out of the blue. On the way to the shop the battery must've drained completely because the dash lit up like Christmas, literally every warning light. Limped into an oil change place and they said it was a bad battery, so I got a new one.

Few days later same issue. Made it to my regular shop this time. They said it was the alternator, put a new one in and it burned out too. Said they traced it back to the PCM. They replaced it and it ran fine for a couple of weeks then SAME ISSUE battery light comes on. Jeep will crank fine until it won't. AC seems weak and doesn't really **** like used to. No cruise control. I could be wrong but the engine seems to have less power and be quieter.

I read it could be grounding issue but from the posts I could find here I checked the grounding wires and they seem visually ok. Any thoughts?

 

[Johnny O]

How’s your serpentine belt looking? And unless the ground rings out good on a meter, it ain’t.

 

[pinhotihiker]

How’s your serpentine belt looking? And unless the ground rings out good on a meter, it ain’t.

Serpentine belt looks fine, but admittedly I don't have a lot of experience with this stuff. I need to get a multimeter to check all the grounds myself, if my shop is gonna keep dragging their feet. I don't even know if I've found all the ground connects

 

[Billwill]

You need to buy a digital Multimeter....a cheap one will do as no fantastic accuracy is required.

Then check the voltage across the battery while engine is OFF, while engine is being turned over by the Starter motor and the while the engine is at idle.

Then measure the voltage at the large lug on the alternator with respect to ground while doing the same actions as above...should have the same results!

Report back on those voltages and then we can go on from there!

 

[Johnny O]

You need to buy a digital Multimeter....a cheap one will do as no fantastic accuracy is required.

Then check the voltage across the battery while engine is OFF, while engine is being turned over by the Starter motor and the while the engine is at idle.

Then measure the voltage at the large lug on the alternator with respect to ground while doing the same actions as above...should have the same results!

Report back on those voltages and then we can go on from there!

Agreed. I highly recommend the Exotech brand. This is the consumer grade of the Famous Fluke brand us twidgets use.

 

[Johnny O]

Just remember to completely disconnect the battery when ringing out grounds or you can smoke your Jeep’s brain box.

 

[pinhotihiker]

Just remember to completely disconnect the battery when ringing out grounds or you can smoke your Jeep’s brain box.

Forgive me, do you mean to disconnect the battery before I disconnect any grounds?

 

[Johnny O]

Forgive me, do you mean to disconnect the battery before I disconnect any grounds?

It is always a good idea to completely disconnect the battery when doing electrical work on Jeeps. They are notorious for bad things happening to the computer otherwise.

id check that every fuse and relay is clean and properly seated along with all the electrical connections too. Parts fiche is your friend.

In your case id disconnect the battery and start with a visual inspection of all the ground straps under the hood AND the ones on the drivetrain. Look for damage corrosion and loose connections. If you see the ground bolts are rusty, carefully disconnect and clean with electrical contact cleaner. When dry, dose them with dielectric grease and reassemble. If damaged or corroded, replace the ground strap with a new one. Dose it well with dielectric grease, working it into the fibers!

Then I’d reconnect the battery d test it out. If your problems persist, then it is time to disconnect the battery again and start ringing out circuit

 

[Billwill]

Yeah when checking grounds disconnect the battery Leads completely but in the advice I gave above you initially need everything to be connected up.

The large lug on the Alternator has a thick cable connected to it which goes directly onto the Positive Post of the Battery.....this is how the charge voltage from the Alternator finds its way to the Positive Terminal of the Battery.

The thing is that this thick cable has a fuse built into it that cannot be seen....this whole cable is called a "Fusable Link".
This "Fusable Link" comes in different colors depending on how much current it can take before the fuse blows. So a Jeep with a 160 Amp Alternator should have a different color to a jeep with a 140 Amp Alternator as the current flow will be higher.

What happens often...especially if you have idiots working on the Alternator...is that they place a wrench on this large lug on the alternator to tighten it or to remove it without first disconnecting the battery completely! The end of the wrench now touches onto engine/chassis and blows the Fusable Link!

So definitely disconnect the Battery completely before testing for loose connections/grounds etc.

Once you have done that.....do the checks with a Digital Multimeter that I mentioned above with everything connected up.

With the Meter set to DC Volts check the battery voltage across the Battery terminals with engine OFF!....should be about 12.5 Volts or better.

Have someone turn over the ignition while you keep the leads over the battery...voltage should not drop below about 8.6 volts while engine is turning over.

As engine fires up the voltage should shoot up to about 13.4 Volts which is your charging voltage.

If all these voltage checks are fine then your Battery, Fusable Link and Alternator are generally in good shape....a bad Battery could discharge itself overnight or there could be something discharging the battery badly ie. a short!

If this all checks out OK then things get very complicated but often it is simply a loose connector or ground that causes the problems! Worst case scenario is having a cable being pinched by some component so that the insulation is broken and the wire inside shorts to chassis/ground or to some other random wire!

Jeep Agents are generally useless at finding such problems...they simply replace components until hopefully something works! An Auto-Electrician may be able to trace the fault!

And yes as LabRat states the Fluke Multimeter is the best of all....I still carry my Fluke from my IBM,Hitachi and Robotic days! But for basic fault-finding a cheaper model does the job...does not have to be 100% accurate but get a Multimeter that can measure DC volts, AC Volts, Resistance in OHMs and DC Current up to 10 Amps

And when you check the Serpentine Belt...make sure that it is routed correctly!