volt gauge at 0

[dripley]

Just got in from and about 8 miles out I noticed the the check gauges light is on and the volt gauge is on 0. Roll in the driveway and put the meter and its putting out 13,8 volts on the charge stud. 

 Not sure what to check now. Ideas anyone???

 

 

 

 

 

 

 

 

 

 

 

 

t

[Dieselfuture]

Your fuse?

[dripley]

And which fuse might you be speaking of? More food for thought, I just went and cranked it again to see if the the other gauges were working and the volt gauge is back to reading a tick under 14 volts. Double 

Edited February 3, 2021 by dripley

[Dieselfuture]

1 minute ago, dripley said:

And which fuse might you be speaking of?

The one you install with WT mod, don't remember how you got yours ran.

I guess that shouldn't effect the gauge, doesn't it go to pcm directly from alternator 

Pcm protection fuse then 

I'm about as good in electrical as you are

[dripley]

@DieselfutureThat would be the fuse I have yet to install. But if that fuse was there and blown the alternator would not put out any voltage correct? The alt was putting out 13.8 while gauge was all the way to the left. And now its reading again. I have not had an electrical gremlin since I did WT's mod, guess I am due one.

Edited February 3, 2021 by dripley

[dave110]

You have a fuse or circuit breaker in the charge wire right? Several here have reported issues with the chinese circuit breaker going wacky

[Dieselfuture]

Where does guage get signal from? Pcm? Cluster talks to pcm? This is above my pay grade @Mopar1973Man would know, I can say more things but don't want to talk for no reason, I do enough of it as it is.

[dripley]

14 minutes ago, dave110 said:

You have a fuse or circuit breaker in the charge wire right? Several here have reported issues with the chinese circuit breaker going wacky

Thats all fine and the alt was putting out good voltage and it was reaching the batteries. The gauge just crapped out for while. Working now.

 

1 minute ago, Dieselfuture said:

Where does guage get signal from? Pcm? Cluster talks to pcm? This is above my pay grade @Mopar1973Man would know, I can say more things but don't want to talk for no reason, I do enough of it as it is.

I believe you would be right on that, but this is above the chicken mans pay grade also.

[dave110]

18 minutes ago, dripley said:

Thats all fine and the alt was putting out good voltage and it was reaching the batteries. The gauge just crapped out for while. Working now.

 

I believe you would be right on that, but this is above the chicken mans pay grade also.

That blows my theory then. At first you said it was putting out 13.8 at the charge stud so I thought maybe your CB was flaking out and the charge was not going anywhere.

[dripley]

19 minutes ago, dave110 said:

That blows my theory then. At first you said it was putting out 13.8 at the charge stud so I thought maybe your CB was flaking out and the charge was not going anywhere.

I did leave that little tid bit out on the original post. But managed to squeeze it in later.

[Mopar1973Man]

1 hour ago, Dieselfuture said:

Where does guage get signal from? Pcm? Cluster talks to pcm? This is above my pay grade @Mopar1973Man would know, I can say more things but don't want to talk for no reason, I do enough of it as it is.

ECM and PCM both talk to the cluster. Fuel Guage and volt gauge is from the PCM. The oil pressure, coolant temp, tach are cover by the ECM. As for speedometer the ABS talks to the cluster.

[dripley]

Looks like mrs pcm got po'd at mr volt meter and they quit talking for a bit. Hopefully the peace they made is long lasting.

[Tractorman]

@dripley, this may be a place to start.  This is the operational description of the voltage gauge from my 2002 repair manual.  This may at least explain why your problem corrected itself for now.

 

Hope this helps,

 

- John

 

Operation

The voltage gauge gives an indication to the vehicle
operator of the electrical system voltage. This
gauge is controlled by the instrument cluster circuit
board based upon the cluster programming and electronic
messages received by the cluster from the
Powertrain Control Module (PCM) over the Chrysler
Collision Detection (CCD) data bus. The voltage
gauge is an air core magnetic unit that receives battery
current on the instrument cluster electronic circuit
board through the fused ignition switch output
(st-run) circuit whenever the ignition switch is in the
On or Start positions. The cluster is programmed to
move the gauge needle back to the low end of the
scale after the ignition switch is turned to the Off
position. The instrument cluster circuitry controls
the gauge needle position and provides the following
features:

† Charge Fail Message - Each time the cluster
receives a message from the PCM indicating a charge
fail condition (system voltage is 10.8 volts or lower),
the gauge needle is moved to the 8 volt graduation
on the gauge scale and the check gauges indicator is
illuminated. The gauge needle remains on the 8 volt

graduation and the check gauges indicator remains
illuminated until the cluster receives a message from
the PCM indicating there is no charge fail condition
(system voltage is 10.9 volts or higher, but lower
than 16.7 volts), or until the ignition switch is turned
to the Off position, whichever occurs first. On models
equipped with the optional diesel engine, the instrument
cluster is programmed to support the voltmeter
gauge needle above the low end of normal graduation
and suppress the check gauges indicator operation
until ten seconds after the engine intake manifold air
heater has completed its cycle.

Edited February 4, 2021 by Tractorman

[dripley]

Thanks @Tractorman. I have had my gauge go to the 8v position a few times over the years, once with a failed alt. This is the first I have seen go dead left just like switch was off. Matter of fact mine goes to the 8v mark at key on then slowly rises towards the 14v mark before it settles there after engine start. I hope its just one off thing since it was working when I went and restarted it. We shall see what tomorrow brings. I do have spare cluster in case something is wrong with it.

I guess I have to eat a little crow. Just went and turned the truck on and the gauge went to 12v and in off position to 8v. For some reason I was thinking the 12 was 8 and the 8 was 0. 

 

Crow aint as good as chicken.

[dripley]

Made it all the way to work no problems. 

[Mopar1973Man]

Ok. 

 

To check the field lead. You need to start the truck and measure the voltage on the blue wire is there +12V? If not the PCM is burned up. Now on the green wire its a "ground" so test the same way using the DVM and it should show -12V or +12V depending on the probe usage. Green side typically will not cause damage but if the blue wire has ZERO volts then the PCM burned up. 

 

As for the charge stud. That should pass through a 150A circuit breaker or 150A fuse or even stock is 140A fuse. If the fuse is blown or circuit breaker tripped then reset and see if it repeats. If it does you batteries might not be up to the task or possibly cables. Check both batteries while charging and see if the voltage is EXACTLY the same if not the bridge cable on the radiator is shot possible.

 

Digging a bit deeper if the field lead has power both blue and green working then it could be the armature brushes and slip rings. If there is no power reaching the armature it will never start to charge. You might be better having your alternator bench tested. 

[dripley]

4 hours ago, Mopar1973Man said:

Ok. 

 

To check the field lead. You need to start the truck and measure the voltage on the blue wire is there +12V? If not the PCM is burned up. Now on the green wire its a "ground" so test the same way using the DVM and it should show -12V or +12V depending on the probe usage. Green side typically will not cause damage but if the blue wire has ZERO volts then the PCM burned up. 

 

As for the charge stud. That should pass through a 150A circuit breaker or 150A fuse or even stock is 140A fuse. If the fuse is blown or circuit breaker tripped then reset and see if it repeats. If it does you batteries might not be up to the task or possibly cables. Check both batteries while charging and see if the voltage is EXACTLY the same if not the bridge cable on the radiator is shot possible.

 

Digging a bit deeper if the field lead has power both blue and green working then it could be the armature brushes and slip rings. If there is no power reaching the armature it will never start to charge. You might be better having your alternator bench tested. 

She ran fine all day today. kept me warm for 3 hours and took where I needed to go. Then about 4 miles from the job going home it dropped out again. This time no charge just battery voltage. I made home alright. I was just going to post up on the field lead. I do have 12v on both wires with the engine running. So it is alternator time. It is 6 years old with 200k on it so maybe I was due. Now to find one, hope to fix it tonight.

Edited February 4, 2021 by dripley

[dripley]

Well no one had an alternator other than Advance. They Car Quest reman for $120. Got 20% of plus 10 with coupon. Got for less than 90 bucks and the truck is charging again. Now to find my good DVM and check the AC ripple. Unfortunately that will have to happen Saturday. Got to work all day tomorrow and wont have time until then. Did not get it tested there because no one knows what to look for. Fingers crossed.