1992 12 Valve not charging

[926shooter]

I have a brand new battery and alternator that tested good, however my truck will not charge. If anyone could help me find the solution it would be greatly appreciated.

Thanks,

John

 

[Simplysmn]

Try changing out the first relay on the fender well it's the ASD relay and help's with charging .If that doesn't work you need a PCM or just put a external regulator on the charging system .

 

[MMeier]

Could also be a faulty CPS.

 

[BDaugherty]

Check the crank sensor. If the tach reads zero, it's a dead giveaway of a cps problem. The pcm will not tell the alt to charge if it doesn't know the engine is running.

 

[926shooter]

where exactly is my ASD relay? if anyone has a detailed answer so that I can start driving my truck that would be absolutely fantastic.

 

[Philip]

On the left side inner fender well are three relays. The relay closest to the battery is the starter relay. The middle relay is the ASD relay. The third relay is for the A/C compressor.

All three relays are a 4 pin style relay. Dodge used 5 pin relay sockets. So eather style relay will work.

 

[DVolk]

Is the guage saying its not charging? as ive seen lots of oem gauges go bad you should be able to full field the alternator to see if its charging or not, a crank sensor has nothing to due with the alternator charging ,in a pinch you can check the ecm with one from a mini van

 

[MMeier]

, a crank sensor has nothing to due with the alternator charging ,

I always thought without a signal from the crank the computer doesn't know the truck is running, therefore the alt will not charge (or turn on), cruise control will not work and for those with automatic trans eqipped trucks, will cause lock up/ OD issues . Anyone else ?

 

[DVolk]

Renember these are mechanical engines not computer controlled , you can pull all of the wires of the engine and connect a hot wire to the pump and it will run

 

[Philip]

Renember these are mechanical engines not computer controlled , you can pull all of the wires of the engine and connect a hot wire to the pump and it will run

The engine will run with only one wire. If the PCM does not see a RPM signal from the CPS. It will not charge. It will not have CC or OD.

 

[DVolk]

No that's not correct look at the wireing info for a mopar alternator simple wiring for in a race car or testing in a book this works on the same principle as the 1990 and down trucks I don't have a ecm or crank sensor on my suburban conversion all the ecm on the latter trucks do is control grid heater and transmission and have the voltage regulator the crank sensor on the front of the engine is for a optional tach only

 

[Philip]

the crank sensor on the front of the engine is for a optional tach only

Wrong

If the 92/93 PCM does not see a RPM signal it will not allow ALT/CC/OD. The PCM has to know the engine is running before it allows these other functions. The CPS is the only way it knows.

 

[cerberusiam]

If the 92/93 PCM does not see a RPM signal it will not allow ALT/CC/OD. The PCM has to know the engine is running before it allows these other functions. The CPS is the only way it knows.

Yep, all of that.

 

[DVolk]

maybe in a auto truck not in a manual truck , so pull the alt and have it checked out at a parts store as im willing to but you don't need any of that hooked up to make the battery charge and id even bet on it and prove it I could see the truck

 

[cerberusiam]

Making it charge and having it charge as intended are 2 different things. If you bypass the SBEC for charging control then yes it will charge if the alternator is good. If the CPS is not feeding the SBEC a signal and that is how the charging system is designed it won't charge. The CPS harness has a plug on the top side front of the engine that gets loose and\or corroded that is the source of a lot of charging problems.

 

[Mikey-KE7LBB]

maybe in a auto truck not in a manual truck , so pull the alt and have it checked out at a parts store as im willing to but you don't need any of that hooked up to make the battery charge and id even bet on it and prove it I could see the truck

Several years ago, I had a '93 D-250 with a manual trans and the belt started to fail. One of the loose ribs took out the wires on the CPS. The volt gauge instantly dropped down to where it normally would read before it was started (12.8V) and the AC and cruise quit working as well. The gauge continued to drop as I limped it home and checked it with a multimeter. It went from a "normal" 13.8V~14.2V all the way down to 9.8V!

I replaced the sensor and all went back to normal. In short, the CPS is needed to tell the PCM that the engine is running before it will charge.

Stock alternator and unmolested wiring will not allow charging without the CPS or PCM functioning. The only way around it would be to have an external regulator or make modifications to the alternator (or wiring) and bypass the signal it receives from the PCM.

If you can tell us what you did to make it work without cooking the battery, I'm sure all of us want to know.

 

[DVolk]

We have never been told if the alternator has been confirmed if its good or if there is 12volt at the alternator . assumeing all is there and correct . If you look in a old chiltons or a old " Motors Manaul " it shows how to do a test to see if it is working or not , some show a simple diagram of how to wire one up those of us that have the mopar race wiring book shows how to wire a alternator there as well these are what is used on my suburban , how ever there is some alternator shops that can convert our alternators to be internally regulated and just need a simple wire hookedto the positive of the battery and it wont cook the battery . The alternator only needs to sense a draw to work that's it !!!

 

[Philip]

maybe in a auto truck not in a manual truck , so pull the alt and have it checked out at a parts store as im willing to but you don't need any of that hooked up to make the battery charge and id even bet on it and prove it I could see the truck

Manual trucks are the same. NO CPS signal looses A/C/ CC and charging also.

your showing a 92 in your sig. Go for a drive and make sure your A/C and CC and alt work. Unhook the CPS plug. Then post back what stopped working.


That test your talking about is called a bypass test. You unhook both field wires. Apply 12 volts to one field terminal. Ground the second terminal. The Alt will charge then if it is a good alt. For the real old Dodge single wire alt's. Just apply power to the one field terminal.

 

[DVolk]

Maybe so because it has the OEM parts , why would it work when ac is un plugged ? but never less the original poster never reported back on what was working or isn't , its mainly just how a rig is wired on ag equipment most of them don't have all the ECMsetc such as my Case 1840 skid steer with a 3.9 it don't have all that BS on it and the baterys don't boil on those

 

[Philip]

Your talking about a different type of equipment made by a different company. Each MFG makes something to what they want it to do and the way they control it. We are talking about a Dodge in this thread. Knowing the proper operation of the PCM and what it controls is needed knowledge.

The IC'd 91.5 models had a PCM with no internal regulator. It used a external regulator. If you set with the key on not running it could discharge the battery over time. The ALT was powered while the key was on. Without it spinning it was draining the battery threw the field circuits.

On a truck with auto trans if the PCM sees a full throttle signal from the TPS. It will drop the ALT/ A/C till the throttle position returns to a lower setting. This is done threw the ASD relay.