2nd Gen Non-Engine/Transmission charging issue

[Graphic man]

i noticed this morning my Volt gage was sitting on about 12Volts at idle (this is after the truck was running for awhile so no grid heaters) as soon as the rpm's came up a little it would jump to 14. 2 it took about 30min for it to stay on 14+V's at idle... seemed to me the volt reg. would not kick in to charge it at an idle,... battery's and alt. . are new about a year ago



does this sound like the battery temp sensor doing this? or an ecm?





Scott

 

[Graphic man]

Bump



anyone?

 

[DKnotts]

Sounds like your alternator may be going bad. True the ecm controls the output via several sensors (batt temp included) but if it jumped to 14v just off idle then to me that would indicate the alternator was doing all it could at idle but wasn't enough til you came off idle so it could make more. More on this in a minute. Another cause could be a larger than normal draw on the system (i. e. the heaters you mentioned) but I was considering a bad battery or shorted wire somwhere. More than likely I would say the alternator is going bad though.

More on the output theory. Alternators have whats known as a diode trio or diode pack as part of the regulator. The output currrent is divided among these diodes. When one fails your current output is reduced by that amount (if 3 which is typical then you have 1/3 less output - 136A dodge standard now would max at 90A). You would not see a charge light or any codes under this condition because the ecm looks for the field in the alternator to be active. A little confusing I know, sorry. The only time you get an idiot light is when all diodes have failed or there is a short in the field wiring (nothing to regulate, regulator gone bad). Field meaning internal to the alternator. So at idle the alternator spins slower and has limited output as it is and if any of the diodes have failed it will be that much more limited.

My suggestion is to take it off and have it load tested at parts store or alt. shop. Also check your batteries INDIVIDUALLY. They must must be disconnected from each other to tell if one has gone bad. This is easy enough simply by disconnecting the ground lead from one of the batteries.

 

[Graphic man]

The battery's were load tested and they are ok (1 at a time)



i will check the charging of the alt.



is there any way of testing the bat. temp sensor ?



Thanks again



Scott

 

[Graphic man]

1 other thing i have seen is the grid heater use to pull the Volt meter down to around 10-12 and for the last 2 years or so it will pull it down to 8-10 when it cycles



it still cycles the same it just pulls the gage down a lot further.



Scott

 

[DKnotts]

I know of no simple way to check the batt temp sensors. Maybe a dealer knows a way other than replacement? On your second note... that would further agree with my suggestion of the alt going south... unless the drawing down condtion continued to exist after you replaced your alt once before (you did say you had replaced it once right?). Something else that comes to mind in you saying the draw down scenario are bad connections. Check thourghly the connection on the back of the alternator, that charging cable and the connection on the other end. I think it terminates in the fuse box? While you're there check the fuse to make sure it's seated properly and good, firm connections. Any sign of arcing or corrosion anywhere along this path is real bad news for your charging system and would certainly reduce the charging capacity of the alternator.

 

[Graphic man]

all connections are clean as a whistle.



the alt. is maybe 2 years old



i'll check the alt and see what i have





Thanks!!!



Scott

 

[JFaughn]

Temp sensors are varyable resistors , put amulti meter on ohm setting , connect so sensor , use a heatgun / hairdryer , to warm up , you should start with some resistance and then very stedily as it warms up .
Maybe some one can give the spec. s , but doing as I discribed above and not having any open circut , meens its working some , working good we would need the spec.

 

[Graphic man]

Temp sensors are varyable resistors , put amulti meter on ohm setting , connect so sensor , use a heatgun / hairdryer , to warm up , you should start with some resistance and then very stedily as it warms up .

Maybe some one can give the spec. s , but doing as I discribed above and not having any open circut , meens its working some , working good we would need the spec.

Now we just need the specs :-laf



thanks for the info!!





Scott

 

[WestTN]

Sorry I don't have more data points, but I measured mine last year and it read 27. 7 ohms at 42 degF and 11. 5 ohms at 72 degF.

 

[Graphic man]

something else is going on to that i seen today for the first time,

truck was shut off for around 5 hrs, -10 C here in Canada and the high idle did not come on





i am thing ECM :{



Scott

 

[JFaughn]

Had to read your origanal post over , 1st your not going to get charging to speek of at idle , need more RPMs to charge , the higher the RPMs the higher the charge , so maybe there was no problem there , now it sounds like you do have a problem , no high idle , temp semsor , but that would be a different temp sensor than the batt. sensor I think , would need to look at a manual , you should get one , from Geno's
Garage , one of the site sponser's here .

 

[Graphic man]

i did have the high idle this morning..... i think the truck did not cool down 100% for the high idle to come on.



i am going to replace the bat. temp sensor to see it that helps and if not a new alt. but i will test the one i have first.



it only acts up 50% of the time..... sometimes it charges just fine at idle and other times it takes 20min or so for it to charge at idle... . but in all cases it will charge once the rpm's are over 1000.





Scott

 

[DKnotts]

Ok, could still be an issue with the alternator, but now it's sounding like it could also be just a draw down issue. The times it's not charging at idle after starting - had it been colder, or longer since the last time you ran your truck vs. times you don't see the issue? One way to know for sure if it's a draw down issue is to use a digital volt meter with 4 digit accuracy (12. 24 vs 12. 2) and read voltage before you start the truck to give you exact knowledge of just how much charge remains in the batteries. If you don't have a meter, such as a Fluke or even Sears makes some decent enough ones, there are fairly cheap cigarette light types (voltage readings only) that would make this easy on you. Point being that if for whatever reason (to be researched later) your batteries are lower the mornings you experience the problems then I would say the "lack" of idle charging would be normal since the batteries are using all the juice but if that theory proves battery voltage is not the charging issue then you're back to other areas of concern. You could borrow a clamp on style DC amp meter and measure the output of the alt when acting normal by loading it down heavily (lay men's load test) and see if you get near 130 amps, that would eliminate the alt as a problem and then you're down to the ecm which determines charging output via batt's temp, batt's voltage and rpm. I think that's it though. It's a matter of tracking the facts really and testing the componets you can.

 

[J Shocik]

I'm just wondering if the right amp alternator was installed when it was replaced?? Did you get it from a major auto parts chain, like Auto Zone? Most of the time they list the wrong one for the CTD's, a 120 amp instead of the 136 amp. A couple of Canadian winters could help prematurely cook a 120. Just my $. 02 worth...

 

[Graphic man]

I'm just wondering if the right amp alternator was installed when it was replaced?? Did you get it from a major auto parts chain, like Auto Zone? Most of the time they list the wrong one for the CTD's, a 120 amp instead of the 136 amp. A couple of Canadian winters could help prematurely cook a 120. Just my $. 02 worth...

you are right ... it could happen..... but no i got the right one for the truck,



the more i drive it the more i think it's the temp sensor... it did the same thing this morning ... ... would not charge unless the rev's were up... . once the truck got to full temp and got some heat under the hood it started to charge again at idle.



i have a new temp sensor on it way, so I'll put it in and see if it fixes my problem.





Scott

 

[Thomas]

... Most of the time they list the wrong one for the CTD's, a 120 amp instead of the 136 amp...

A look at the ratings table in the 2001 FSM suggests both the 120 amp & 136 amp listings might be referring to the same alternator.

-

 

[jelag]

I've got to chime in here... . one of the most common problems with idle charging is a loose drive belt... I can't tell you how many times I've been able to grab the pulley on the front of the alt and turn it... when it had a fan blade, the common test was to put your thumb on the fan and push... if you could move the pulley the belt was too loose...



Something as simple as this can cause a problem with failure to charge at idle and if you add a worn belt where the belt needs to warm up to grab or its never been treated with a belt conditioner than the problem is worse...



Hope the simple fix takes care of it...

 

[Graphic man]

I've got to chime in here... . one of the most common problems with idle charging is a loose drive belt... I can't tell you how many times I've been able to grab the pulley on the front of the alt and turn it... when it had a fan blade, the common test was to put your thumb on the fan and push... if you could move the pulley the belt was too loose...



Something as simple as this can cause a problem with failure to charge at idle and if you add a worn belt where the belt needs to warm up to grab or its never been treated with a belt conditioner than the problem is worse...



Hope the simple fix takes care of it...

first thing i checked when all this started happening !!





Scott

 

[WTurney]

My Voltmeter has done this since new... truck is idling (cold) and the headlights dim with the dips in the meter... other trucks I've seen in this generation have same perk... all has been checked and never had any problems.