2.9 Alternator

[RonD]

Well the alternator didn’t fix the issue. Still having to jump the Bronco to start it. Something is killing the battery. Immediate restart after shut off works, if I wait 10 seconds an try to start I got nothing.

Electrically this doesn't make sense, lol
Especially if you are connecting jumper cables to the battery cables on the battery

The vehicle's battery cables are connect on their inside surface to the battery posts
If you connect jumper cables to the outside surface of those same cables and vehicle starts that would mean the cables themselves are OK, but the inner surface is not making good contact with the vehicle's battery
OR
The starter motor is bad, and needs TWICE the AMPS(two batteries) to crank engine over

Electricity(AC or DC) needs a "circle", a circuit, in order to work
In the case of vehicles that means a connection to positive and negative electrical terminals
And the circle needs an EQUAL pathway for both + and -
If the positive battery wire can pass 70amps, but the negative wire can only pass 20amps, then that circuit(circle) is limited to 20amps

In the case of starter motors that need 50-70amps instantly to crank/turn the engine the positive AND negative cable's connections to the battery AND the vehicle matter a lot, both need to pass, the up to, 70amps required

That's why the jumper cable thing has me puzzled

And there is no drain a vehicle can have that would drain a good battery in 10seconds, or 10 min, to prevent a restart
There would be a smoke show, lol, if that was the case

And if at rest battery voltage was 12.4v after 19 hours then its a good battery

 

[Mhfco6]

Electrically this doesn't make sense, lol
Especially if you are connecting jumper cables to the battery cables on the battery

The vehicle's battery cables are connect on their inside surface to the battery posts
If you connect jumper cables to the outside surface of those same cables and vehicle starts that would mean the cables themselves are OK, but the inner surface is not making good contact with the vehicle's battery
OR
The starter motor is bad, and needs TWICE the AMPS(two batteries) to crank engine over

Electricity(AC or DC) needs a "circle", a circuit, in order to work
In the case of vehicles that means a connection to positive and negative electrical terminals
And the circle needs an EQUAL pathway for both + and -
If the positive battery wire can pass 70amps, but the negative wire can only pass 20amps, then that circuit(circle) is limited to 20amps

In the case of starter motors that need 50-70amps instantly to crank/turn the engine the positive AND negative cable's connections to the battery AND the vehicle matter a lot, both need to pass, the up to, 70amps required

That's why the jumper cable thing has me puzzled

And there is no drain a vehicle can have that would drain a good battery in 10seconds, or 10 min, to prevent a restart
There would be a smoke show, lol, if that was the case

And if at rest battery voltage was 12.4v after 19 hours then its a good battery

Yea I’m puzzled too. Jumpbox would start it, but after a 10 second shut off it would not start back up. I just put a charge on a battery, stamped 2019 out of another vehicle reading 11.6. Charged it for 1 hour and put it in the Bronco and is started right up. Ran truck for 15 minutes and battery reading was 14.29. Shut it off and it started back up. Shut it off for 10 mins and it started back up. Now I’m suspecting the battery that tested good.

 

[RonD]

Certainly possible for a battery to show volts but have no AMPs

As said above both + and - must have equal flow of AMPs
So if one terminal inside the battery has limited AMP passing then it would show good voltage, so no internal short(self draining) but can't provide required AMPs for start up
Not a common failure in car batteries, but a possible failure for sure

 

[franklin2]

If you have a meter you can do some tests if you have a helper.

Put your meter on DC volts, put the probes right on the center on the posts of the battery. While holding them there, get someone to try to start it while you watch the meter and hold the probes. If it does all that buzzing and won't start, and your meter shows 12v or higher, the battery is good. If the voltage drops to a very low value, the battery is bad.

If the voltage stayed high but it would not start in the first test, tell your helper not to go anywhere. Take your probes and move them to the battery clamps themselves around the posts. While watching the meter, tell them to try and crank it. If the voltage drops really low, you have a bad connection on the battery terminal, one or the other. If the voltage stays high, then move on.

The next place to check is put the negative meter lead on the battery post, put the positive meter lead on the large stud on the solenoid that goes to the battery. While holding the meter probes here, get them to try and start it again. If the voltage drops low, then your short positive battery wire is bad. If good, then next

Move the meter negative lead to the engine block on a bare place for a good connection. Move the positive meter lead to the positive post of the battery. Then get your helper to try and start the engine. If the voltage drops low, your negative battery lead is bad.

See what we are doing? We are checking for voltage WHILE SOMEONE TRIES TO CRANK THE TRUCK. Poking around with the meter doing checks without holding the key to crank position tells you nothing. You need to put a load on the circuit while you are checking voltages. You can work your way all the way to the starter. If you have 12v at the starter when the helper tries to crank it, and it will not go, the starter is bad.

 

[Mhfco6]

If you have a meter you can do some tests if you have a helper.

Put your meter on DC volts, put the probes right on the center on the posts of the battery. While holding them there, get someone to try to start it while you watch the meter and hold the probes. If it does all that buzzing and won't start, and your meter shows 12v or higher, the battery is good. If the voltage drops to a very low value, the battery is bad.

If the voltage stayed high but it would not start in the first test, tell your helper not to go anywhere. Take your probes and move them to the battery clamps themselves around the posts. While watching the meter, tell them to try and crank it. If the voltage drops really low, you have a bad connection on the battery terminal, one or the other. If the voltage stays high, then move on.

The next place to check is put the negative meter lead on the battery post, put the positive meter lead on the large stud on the solenoid that goes to the battery. While holding the meter probes here, get them to try and start it again. If the voltage drops low, then your short positive battery wire is bad. If good, then next

Move the meter negative lead to the engine block on a bare place for a good connection. Move the positive meter lead to the positive post of the battery. Then get your helper to try and start the engine. If the voltage drops low, your negative battery lead is bad.

See what we are doing? We are checking for voltage WHILE SOMEONE TRIES TO CRANK THE TRUCK. Poking around with the meter doing checks without holding the key to crank position tells you nothing. You need to put a load on the circuit while you are checking voltages. You can work your way all the way to the starter. If you have 12v at the starter when the helper tries to crank it, and it will not go, the starter is bad.

I tried this and didn’t get very far, the + battery to solenoid drop was like 10v. That’s when I changed the battery. I’ll let you all know if this keeps on or if the newer battery helps. Thanks again to all.

 

[Mhfco6]

Just went out to start it for giggles and it started right up, shut it down cranked it again.. it seemed slower. Tried it again, much slower. Tried it again and wouldn’t start.

 

[franklin2]

Sounds like the battery doesn't it? I know batteries are expensive. You can try what I do and possibly save some money. I go to some of the parts stores, and the interstate battery stores, they sell "used" batteries. They are around $50. They are not used batteries, they are batteries that sit on the shelf too long and they pull them and can't sell them as new anymore, even though they have never been "used". I have had good service out of these batteries. You have to be a little flexible sometimes, the batteries they have might not be the exact battery your truck calls for, but many different batteries will fit, you just need a tape measure. And sometimes you can turn the battery around to make the cables work.

 

[Dustin_89BII]

I had an electrical gremlin recently in my ‘89 B2. It seemed like the alternator was bad because the battery would drain while driving. Pretty new battery. Charged it up and got 12.8v or so. I’d turn on the truck and the volts wouldn’t move. (Looking like the alt wasn’t adding voltage to 14.5 ish). Then the battery would slowly drain as you’d expect with the alt not functioning.

I did eventually figure out the problem. It was the ignition lock cylinder.
I’d crank the engine and it would start right up. But what was happening was that the cylinder was allowing the key to sit in the crank position even though it wasn’t cranking. But it was killing power to the alternator and various accessories as if it was cranking!

I had done all the tests like mentioned in previous replies, and did the 10point alternator tests in the ford mechanics manual. Nothing concrete. All tests indicated that the alternator was good.

 

[Terrys87]

With Starters and Alternators, look for a local mom and pop shop. They usually do a great job of rebuilding them. I have had so many part store bad out of the box.

As far as other test, I would check all connections and give a good cleaning. Check all grounds. There are several thru out the truck.

Might try pulling one fuse at a time and let it sit over night and install it before you go to work or next drive. That could help you determine maybe which circuit it is on. Electrical is not my strong point.

 

[Mhfco6]

Knock on wood, all has been well. I’ve picked my daughter up from the bus stop everyday this week and started right up. Took it to Walmart this evening and do great. I’ve got to find some new headlights!

 

[Mhfco6]

Today while pulling out of a parking spot my steering was real hard, had to yank the wheel to get it back straight. 30 mins later a bunch of lights came on the dash then started getting dimmer and dimmer, also noticed my overdrive wasn’t working. Then finally I had no engine power. Found the harness going from alternator to the main feed on drivers side caught and tangled up in the steering shaft. Plugged back in an wrapped with electrical tape and back on the road after a jump start. Wonder if this was my issues all along and not the alternator.

 

[franklin2]

That harness would need a lot of slack in to to fall down and get tangled in the steering shaft. There are some other wires crossing from the engine to the driver's side inner fender. Are they ok?

You can also unplug all those wiring plugs over there and check for corrosion. I have had two of these vehicles now, both a ranger and a BII and both had the same problem, when making a left turn the front drivers side tire throws water, salt, mud, etc. all up over this electrical. I ended up attaching a rubber piece that hangs over the steering shaft to shield it on both vehicles and it stopped it.