Codes: 0562, 1300, 0301, 0303.
Symptoms: low on power, battery light, then M&S lights flash and limp mode, then loss of power at gauges and barely powered home (last 1/4 mile)

Background: have dealt with power issues multiple times over the last year or so.
Alternator bench tested as good, same with battery. So I used the ole multi-meter (thanks Cosmo) and discovered that the positive lead at the alternator was only getting about .78 volts at best while the negative side had a steady 11.75 volts. Apparently I'm losing voltage somewhere between the battery and the alternator in the positive cable/wiring.

My question is: what are my options to fix this? Do I need to find out more precisely where my cable/wires are bad? Or can I easily replace the wiring between the positive battery cable and the positive alternator lead?

I'm very raw and completely inexperienced in the electrical and wiring world, but I'd like to tackle this and get her stronger than ever.

Thanks in advance, DIIB

 

You need between 13.6 ands 14.4 volts to handle your ECU. Go get it checked at a local parts store for free, if the alternator is bad, don't buy a rebuilt one, they have a very high failure rate, buy a new one from British Parts of Utah and be done with this on going low voltage issue.

 

Sounds like alternator has died and is not charging battery - but could be a blown fuselink.

1. With truck off, measure volts across battery. Should be above 12 volts, but might not be if alternator dead. Let's say that it is 12.6 volts.

2. With truck still off, measure volts from (-) battery cable to big brown cable on back of alternator. Should be same as reading across battery.

3. If volt reading from alternator big wire to battery negative is zero, or very low, suspect that the 150 amp fuselink #1 in the under hood fuse box is blown, cracked, or has loose mounting bolts. You can read for volts to (-) battery on the mounting bolts on each side of that fuselink, it should read 12 volts + on both sides. All with truck not running. That fuselink is the big one in the fuse box picture attached. Be sure all those cables at the front are clean and tight.

4. Crank truck, if you can, or jump off truck and crank. Meter volts across battery - should be 13.8 - 14.4. If volts have not gone up from step one the alternator is not charging. Check from (-) battery to small brown / yellow wire on back of alternator, should be above 8 volts. That is the exciter voltage that "turns on" the alternator. If no volts, check fuse 27 in passenger compartment fuse panel.

 

Already had both the battery and alternator tested for free. Also took out the alt and had it bench tested to be sure...though the only report I got back was "tested good" from the machine.

Again, I used a mutli-meter to test the wiring between the battery and the alternator for both resistance and voltage. The negative lead had minimum resistance (.06) and 11.75 volts (which is what my battery is putting out currently from not having the alt work). However, my positive lead had high resistance (around 160 I think) and minimal voltage at the alt connection (.78 volts).

So with THAT info - I'm led to believe there is a problem in the wiring between the battery and the alternator on the positive side. Does this sound right?

 

If you do not read battery voltage (11- 13 volts) at the alternator big wire, to ground (like alternator case, if that is easier) like mentioned above, then that wire goes to the underhood fusebox. The connections can be loose in the picture, or the main fuselink (150 amp) can be bad. Connectors on ends of battery cables should be examined and clean and tight as well.

It would be unusual for one of those wires to be bad under the insulation where it could not be seen. They are the largest wires in the truck. Bad connections, or bad fuslink is far more common. Now if you read from the big alternator bolt brown wire / red sleeve to the brown wire in the underhood fuse box, that is one end to the other, and you read 160 ohms, then yes, that would be strange and a problem. But it is rare.

 

1. 11.75 volts each time I tested it.
2. Did this, same 11.75 volts at negative terminal of alt.
3. Wasn't low, and the under hood fuses and connections appear good.
4. Did this too, but don't remember my readings. Will do again, as well as check passenger compartment fuse panel. I did check drives fuse panel and #25 was bad but I don't think that is related (fog lights?).

Thanks for the charging & starting diagram...I was looking for that earlier!

 

Right. Ends of battery cables are good, connections are clean and tight.

HOWEVER, the wiring between the battery and alt is NOT exactly pristine, it is the way I bought the truck. There are breaks in the casing and electrical tape wrapped around some parts. But it is the smaller wire and connection to the back of the alt (positive lead?) that is shady at best and a much smaller gauge wire.

 

Like we said above, there be 2 wires on the alternator. The big one runs everything in the truck, and has enough amps left over to recharge the battery after cranking. The small one is a (+) voltage thru the battery light bulb in the instrument cluster. The battery light should come on when truck key is turned, after it cranks it should go out. The small wire on the back of the alternator is expected to have positive voltage when truck is switched on, that tells alternator to make the power. It is a small wire and only need less than a couple of amps I think.

So both wires on back of alternator should have (+) volts with respect to frame ground when truck is running.

So if you open the fuse box under the hood, can you meter for 12 volts to ground from the big brown wire? From both sides of the big fuse link (FL1)?

Are you able to open the files sent previously?

 

OK, I'm going to start from scratch and test everything again after work today (or tomorrow). I will start with battery post to post for voltage (was 11.75 but without power from alt this seems ok), then battery to alt off, then battery to alt while truck running. Should the last test be in that 13.6-14.6 range with truck running?

Any help with what I should be testing and how to test would be great...as well as what values I'm looking to achieve so I can identify what's out of spec.

Thanks again.

 

Test 1 - voltmeter across battery terminals - looking for 12 volts or better, but will depend on if charge from alternator is reaching the battery. Less if battery is discharged.

Test 2 - crank truck. Volts should come up to 13.8 - 14.4 volts at idle, no extras turned on. Will this charge up a weak battery? Maybe, but takes awhile, not just a few minutes. Better if you can charge battery with small charger overnight. If OK go to Test 3. If bad go to step 5.

Test 3 - with truck running, turn on things that draw lots of amps, like AC, blower on high, head light on, wiper. Volts across battery should not be below 13.2. If it is by quite a bit, alternator may have a bad diode or regulator and can't keep up with normal demand.

Test 4 - turn off truck and all gadgets. Read battery. While reading, switch on head lights. If volts from this moderate load drop volts to 11 or less, would suspect batttery really isn't fully charged, or perhaps has a weak or dead cell. A battery in that condition can read a good charging voltage, but when called upon for more amps the voltage drops off like a stone.

Step 5: check wires on back of alternator for voltage, + meter lead on wire stud, (-) meter lead on alternator case. Be sure meter leads stay away from rotating parts and belt, same for pony tail or dreadlocks, fingers, etc. Big cable should read battery volts, small cable should read positive voltage. With truck running. If no positive volts on small wire, check fuse 27 under dash. If fuse OK, look at connectors and junction points shown on the RAVE electrical plan. Normally the battery trouble light will show up on instrument cluster at start up, then go out. This light is just under the tachometer on the D2. It MUST come on at startup for just a moment. If not, there is no charge function from the alternator.

If both wires read good voltage on back of alternator, like the big one is 13.8 - 14.4, then read again from frame ground to the brown and red wires in the undehood fuse box - front. Also read each side of the 150 amp fuse link 1 for volts to ground, should be 13.8 - 14.4 volts. If fuse link was bad, alternator could be good, and the charging volts from it could not reach the truck or the battery. With an 11.75 volt battery reading, this would show up as 11.75 on one side of the fuselink to ground vs around 14 volts on the other side to ground.

If you do the above tests and believe alternator is bad, then have tested at parts store # 2 if possible. Murphy's Law applies to new store employees and test equipment as well as DIY mechanics.

In summary, 12 volts from the battery is fed thru fuses and the ignition switch to the battery warning light and on thru some connectors to the small wire on back of alternator. Big wire on alternator brings the amps back to the underhood battery boxk where it flows to the battery and all the loads of the truck.