Archived 98.5 not charging.

[Ken Roberts]

Halfway to work, the Mighty Dodge seems to have lost it's ability to charge the battery. Voltage reads 11.97 running and not running. I replaced the alternator and the issue is not resolved. Where do I look next? Thank you for all help to come.

KenR955

 

[Missouri Mule]

Check your gauge. Not home right now so can not look at fsm to tell you how.
I wil have to check it out but I believe the voltmeter doesn't register un less key is in run position. Pgcm should be sending voltage reading to gauge.

 

[Ken Roberts]

Multimeter shows voltage on both sides of the alternator fuse. I assume that fuse is good. Voltage readings were taken with a meter DVM not from the gauges.

 

[DavidC]

Not sure with 98.5 but my 99 has a sensor under Drivers side battery that stops the alternator from charging if the battery gets hot. I would check that first before getting in to deep.

Dave

 

[Kirwin]

Is the Tach working? if its not working, speed sensor on the front of the engine is bad or miss adjusted or wiring to it has failed. The ECM must see engine RPM to turn on the alternator.

 

[Ken Roberts]

OK, update time. I'm home. I charged the batteries with a co-workers car, it was enough to get me home. When I left the job, non running battery voltage was 12.15 After a 2 hour drive home, the batteries measured 11.12 not running, 10.87 with the engine running. I will do some trouble shooting tomorrow.

Kirwin,The tach was working fine.

DavidC, How do I check the sensor to see if it is working properly?

Thanks Guys!

 

[Ken Roberts]

After thinking about this, I will say that I have noticed that the headlights have been like candles for a few weeks or so. Last Friday I noticed that the cigar lighter outlet by the ashtray didn't have enough power to allow the GPS unit to run, I had to plug it in using the upper power outlet. Perhaps a new alternator will do the trick. Batteries were replaced 3 weeks ago.

 

[DavidC]

OK, update time. I'm home. I charged the batteries with a co-workers car, it was enough to get me home. When I left the job, non running battery voltage was 12.15 After a 2 hour drive home, the batteries measured 11.12 not running, 10.87 with the engine running. I will do some trouble shooting tomorrow.

Kirwin,The tach was working fine.

DavidC, How do I check the sensor to see if it is working properly?

Thanks Guys!

The sensor should be normally closed, opens when hot. An ohmmeter across the 2 leads should show continuity not an open.

Dave

 

[DavidC]

From 99 service manual

BATTERY TEMPERATURE SENSOR
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.

Dave

 

[DavidC]

Forget what I said, found the procedure

BATTERY TEMPERATURE SENSOR
To perform a complete test of this sensor and its
circuitry, refer to the appropriate Powertrain Diagnostic
Procedures manual. To test the sensor only,
refer to the following:
(1) The sensor is located under the battery and is
attached (snapped into) the battery tray (Fig. 1). On
models equipped with a diesel engine (dual batteries),
only one sensor is used. Location is under battery
on drivers side of vehicle. A two-wire pigtail
harness is attached directly to the sensor. The opposite
end of this harness connects the sensor to the
engine wiring harness.
(2) Disconnect the two-wire pigtail harness from
the engine harness.
(3) Attach ohmmeter leads to the wire terminals of
the pigtail harness.
(4) At room temperature of 25° C (75–80° F), an
ohmmeter reading of 9,000 (9K) to 11,000 (11K) ohms
should be observed.
(5) If reading is above or below the specification,
replace the sensor.
(6) Refer to the Removal and Installation section
for procedures.

Dave

 

[Ken Roberts]

David,
I tested the sensor and it reads 32.70K-ohm But it is 18 degrees outside, not 70-80 degrees. I'll replace the sensor anyway, it seems simple enough. Thanks for the tip.

 

[Ken Roberts]

Replaced Battery temp sensor. Same problem. Replaced alternator, had to R&R the pulley with the one on the failed alternator. Yep, all is good. Took the old alternator apart and the brushes were at the end of their travel and not fully touching the commutator shaft. The shaft had deformed where the top brush touches it, I have no idea if just replacing the brushes would have worked.
Thanks for the help. I'm glad to call the TDR folks my friends!

KenR955

 

[DavidC]

Halfway to work, the Mighty Dodge seems to have lost it's ability to charge the battery. Voltage reads 11.97 running and not running. I replaced the alternator and the issue is not resolved. Where do I look next? Thank you for all help to come.

KenR955

I thought you already replaced the alternator ?. Glad it is fixed now

Dave

 

[Ken Roberts]

Yep. Turns out the first one was a new defect. Who knew?