Trying to figure out what's going on with our X. Yesterday took the kids to school, wife to work drove it for about an hour and parked it. Went to retrieve a rug rat from Preschool about 2 hours later and it wouldn't start. Jumped it, drove about 15 minutes & dropped off lunch to wife. Tried to pull away and it stumbled and died. Wouldn't restart. I thought it was a air/fuel issue as it had <1/4 tank and hasn't had the Hutch/Harpoon done yet. Filled it up, jumped it last night. Idled about an hour, then ran some errands. Did just fine. Started this morning without a hiccup. Drove about 20 minutes, dropped kids off, tried to pull away from the school and repeat yesterday's performance. Jumped it, went to Advance to have it checked. I battery showed 12.8ish volts. Other showed 0. They kept the 0-volt battery and charged it up & it tests "good." They said it seemed like the alternator wasn't charging the batteries.

I'm confused though, would the truck be able to even run without the alternator? If it gets jumped to start wouldn't it just die as soon as the jumper cables get disconnected? When we jumped it, I hooked up the cables and ran the van @ 2K RPM for about 10 minutes before trying to start the X, would that have given it enough power to cruise around town?

Lost, trying to avoid the part where I just write somebody check... HELP!

 

The truck will run on batteries without being charged for about 15 minutes, depending on what is running in the cab. An engine with a non-charging alternator would die as soon as the batteries were empty, not as soon as the cables were disconnected. By hooking the batteries up to the van you were charging the batteries. No telling how much you charged the batteries that way, but you did charge them. The key here is that it did run, but wouldn't start. That points to batteries.

The likelihood is that the battery that read 0V is not holding a charge (is worn out), since the batteries are in parallel. Parallel batteries with a bad alternator will drain both batteries about the same. Nearly any battery will pass a battery test right off the charger stand. To check batteries at my house, I charge at low amperage for 24 hours, let the battery sit disconnected off the charger for 3 hours, then test. Parts stores charge for a few hours and test immediately after. If either battery is bad, REPLACE BOTH AT THE SAME TIME.

An alternator is easy to check, and even half-*** mechanics should have the tool to check. I have a battery / alternator / starter checker in my kit, they are about $50.

 

Both batteries are "new" we bought them back in July. I was hoping it was just a bad cell or something, and just now rearing it's ugly head with the cold. However, it's been about 4 hours since the "0" battery got charged. Showed ~12.8v then and still the same now. This makes me assume it's holding the charge. Put the battery back in the truck and checked voltage on both batteries again just to be sure, both showing ~12.8v. Truck started just fine, it's currently idling in the driveway with everything I can think of turned on. Current voltage is 12.0v, with it running shouldn't it be closer to ~14v?

Two more questions:
-Does it matter if I check the voltage when it's running across the battery posts or from the positive post to a ground?
-Assuming the batteries aren't getting charged by the alternator would the voltage I'm measuring slowly drop? Say down to 11.5, then 11.0, etc...

 

The charging voltage should be 14-16V with the engine running at any RPM and everything turned on. In order to run the engine and charge the batteries, you need 14V minimum.
Check the battery voltage across the posts, not to ground. If the engine is running, the voltage across the battery posts will be reading the charging voltage. If it is not running, you will be checking voltage of both batteries collectively. Disconnect the ground wire of one battery to check individual battery voltage.
The voltage will drop as the batteries run out. This is a result of more power used by the truck than created by the alternator. Batteries should remain about the same voltage as they run down.

I am changing my recommendation based on new information. First, have the alternator checked, then possibly replaced, preferably rebuilt by a local alternator rebuild shop.

 

Voltage is now down to ~11.8v, leaving to go get alternator checked out!

*****

Drove & got it checked out. Tech said the system was charging then not, then it was, then not. Got home and it was putting out ~13.0v, left it idling for about an hour. Still same voltage. Turned every electrical device back on, within 10 minutes voltage down to 12.2 and continuing to drop. Found one place locally that will rebuild alternators. Or I can get a new one with a lifetime warranty from O'Reilly's for $189. Rebuild is tempting, I forgot to ask them for cost and now they're closed.

 

if it is a reputable rebuild shop, go with them. the parts store rebuilds usually just replace what is bad.

you may pay $189 for an alternator with 200,000 miles on it that only had the internal voltage regulator and brushes changed.
i have seen parts store"rebuilds" that have armatures that are so bad a reputable shop would throw them away before reusing them.

 

A reputable rebuild shop will be the best bet. Hands down. Last alternator I had rebuilt cost $100 and lasted until I drowned it in oil from an oil leak.

 

I'd also advise to stay away from the parts store reman alternators. Most are remanufactured in mexico and they simply dont last long. I had mine rebuilt a couple months ago at a local shop for $90 with a 1 year warranty. Plus you get to support your local economy!

 

Finally got a chance to get the alternator out (If I knew it would only take 5 minutes I would have done it sooner.) See that label in the first pic? The second pic makes me uneasy about having it rebuilt... I'm not going to get a reman from a parts store, thinking about a new one though. Opinion on getting a reman one rebuilt? Or should I just check with the place that I'd have do the rebuild? And the connector in the last pic: The plastic cover is brittle/broken and that connector doesn't look too good. How hard is it to get another connector on there? And is there a way to keep that connection covered? I'm thinking the little black plastic piece isn't still being made.

 

If a local shop does it, they don't want it to come back. Usually local shops do a good job. I would ask around for the shop reputation.
Also, make sure you get a quote for a complete rebuild.

That charge cable looks like it was fried at one point. You can get the protective boot, usually from the parts store or dealer.

 

a local rebuilder will not care if it was parts store reman or not. the only thing they usually use is the case and armature core that they rewind.

 

Remember to ck the voltage at the alternator if expecting 14.2-14.4 volts. If you check off the batteries, there will be some loss due to resistance between the alt and battery. Expect the voltage to be more like 13.4-13.6 at the batteries if they are good.

 

Every time I check at the battery posts, it's 14-16VDC. On good cables and connections you shouldn't have that much voltage drop.

 

Really?
Is that with a digital VOM?

 

Yes, with an in-calibration Fluke meter (DVOM)