my alternator is not charging

[NathanHerf]

I just put a new one on and then took it back and retested it. Asd, fusible link, alternator and all cables are good. Will my battery temp sensor cause that our its it my pcm

 

[JPNinPA]

Yes battery temp sense sets the recharge voltage based on temp. Hotter battery will see lower voltage.

Clean your battery terminals and the ground connections.
Measure the voltage at the battery engine off and engine running. Do you have aftermarket products hooked up like an amp, lights, wench...?

Have your battery load tested to be sure it could hold a charge.

 

[NathanHerf]

I have all aftermarket stuff unhooked and i have my bat temp sensor pulled out away from my battery. I will check out my grounds and check the volts tomorrow. i appreciate the help. Let you know what turns out

 

[JPNinPA]

Be sure the bat temp is plugged in. It is only a concern when hot out or the sensor is bad. What year and engine jeep?

 

[NathanHerf]

I bet it is that sensor. What kind of voltage should i be getting in those wires on the alt coming from the pdc or pcm dunno for sure where they come from. It is a 98 Wrangler 4.0

 

[SteelHeadz]

The battery temperature sensor is used to determine the battery temperature and control battery charging rate. This temperature data, along with data from monitored line voltage, is used by the PCM to vary the battery charging rate. System voltage will be higher at colder temperatures and is gradually reduced at warmer temperatures.

1. Disconnect the two-wire pigtail harness from the engine harness.
2. Attach ohmmeter leads to the wire terminals of the pigtail harness.
3. At room temperature of 25° C (75 - 80° F), an ohmmeter reading of 9,000 (9K) to 11,000 (11K) ohms should be observed.
4. If reading is above or below the specification, replace the sensor.

CHARGING SYSTEM RESISTANCE TESTS

These tests will show the amount of voltage drop across the generator output wire, from the generator output (B+) terminal to the battery positive post. They will also show the amount of voltage drop from the ground (-) terminal on the generator to the battery negative post.
A voltmeter with a 0 - 18 volt DC scale should be used for these tests. By repositioning the voltmeter test leads, the point of high resistance (voltage drop) can easily be found.
PREPARATION

1. Before starting test, make sure battery is in good condition and is fully-charged. See Battery for more information.
2. Check condition of battery cables at battery. Clean if necessary.
3. Start the engine and allow it to reach normal operating temperature.
4. Shut engine off.
5. Connect an engine tachometer.
6. Fully engage the parking brake.

TEST

1. Start engine.
2. Place heater blower in high position.
3. Turn on headlamps and place in high-beam position.
4. Turn vehicle interior lamps on.
5. Bring engine speed up to 2400 rpm and hold.
6. Testing (+) circuitry:
   1. Touch the negative lead of voltmeter directly to battery positive post.
   2. Touch the positive lead of voltmeter to the B+ output terminal stud on the generator (not the terminal mounting nut) Voltage should be no higher than 0.6 volts. If voltage is higher than 0.6 volts, touch test lead to terminal mounting stud nut and then to the wiring connector. If voltage is now below 0.6 volts, look for dirty, loose or poor connection at this point. Also check condition of the generator output wire-to-battery bullet connector (if equipped) Refer to iring for connector location. A voltage drop test may be performed at each (+) connection in this circuit to locate the excessive resistance.
7. Testing (-) circuitry:
   1. Touch the negative lead of voltmeter directly to battery negative post.
   2. Touch the positive lead of voltmeter to the ground terminal stud on the generator case (not the terminal mounting nut) Voltage should be no higher than 0.3 volts. If voltage is higher than 0.3 volts, touch test lead to terminal mounting stud nut and then to the wiring connector. If voltage is now below 0.3 volts, look for dirty, loose or poor connection at this point. A voltage drop test may be performed at each (-) connection in this circuit to locate the excessive resistance. This test can also be performed between the generator case and the engine. If test voltage is higher than 0.3 volts, check for corrosion at generator mounting points or loose generator mounting.

 

[NathanHerf]

I put a new bat temp sensor on i have checked and cleaned all connections ohm tested all cables and still have nothing.

 

[JPNinPA]

Did you measure battery voltage engine off and running? What did you get?

How about cleaning and inspecting the wires? The method above is straight forward.

 

[NathanHerf]

Fyi in case anybody has the same problem pcm was fried