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Discussion Starter · #1 ·
I have a 1993 Dodge 250 3/4 ton truck with the cummins 5.9 liter turbo diesel engine. I have a power drain that I can't locate. I've just replaced the alternator and the battery to no avail.

Simptoms are: The heater grid light or wait light and the water in fuel light no longer lights until the truck just cranks over with the key on. Once the key is released the lights go out. They do not come on with the key in the first detant position or ignition on only before cranking.

The truck will run fine until the battery is drawn down to nothing. All of the lights go dim including the headlights and dash lights. Could this be that the relays are bad for the heat grid system? How would you trouble shoot this problem. Any help would be greatly appreciated.

This truck is my only means of transportation to work.

Thanks

Dave:confused013:
 

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IIRC, the regulator is a seperate piece from the alternator, so your regulator could be bad, and just not charging, even though the alternator and battery are both good...

Mike
 

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Discussion Starter · #3 ·
Iirc

Mike:

Where is the regulator located and what does it look like? Would it cause the wait light not to come on?

Thanks for your help.

Dave

PS: I'm more familiar with the alternator regulator being on in the same.
 

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I gather that it's actually IN the ECM if it's an automatic... I've got a manual, and I don't know where it is on them... I'm kind of a newb to the Cummins (and Dodges in general), but it's just what I've gathered here... Somebody can either answer this post (please?) or you can trace the output wire from the alternator, and see where it goes...

Mike
 

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ECM stands for "engine control module", but it only controls the transmission on these... I have no idea where it is...

I have heard that some people just put in an aftermarket voltage regulator, and completely skip replacing the one in the ECM...

I don't know anything other than that... You might use the search function at the top, and will probably find what you're looking for... Use "advanced search" and select just this forum (89-93)...

Mike
 

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voltage regulator

in the early 89 90 the voltage regulater is located on the firewall just above the rear of the motor. Mine I think just went bad as well. Some of the "Autozone" ones will not last too long so check your voltage occasionaly. I picked up and new one today and plan on frrezing my fingers off tonight to get it on in hopes of it solving my issue.

Good Luck, keep us posted
 

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Discussion Starter · #9 ·
So, I have no charging from the alternator. I read all of the old posts and got an education, but it hasn't helped me much. I have learned that the crank positioning sensor controls the alternator circuit through the PCM.

So, I've tried to check the Crank Position Sensor to see that it is ok and I'm not sure. The wires look ok, but I'm not sure how to test it. I did find a thread on testing it, but if I unplug it from the harness and check the plug coming from the harness I get no voltages at all.

I'm not getting any charging from the alternator at all. I did try to check that as well with a meter and it seems to put nothing out at all. I connected the meter to the field windings and got nothing. I placed the meter on one of the small nuts on the back of the alternator and read no voltage from it, so I tried the other and got nothing. Would this mean a bad alternator even thought it's been replaced?

Is there a straight forward procedure to test each possibility using a meter? At this point I'm not sure I'm testing each component correctly. I can't believe a new alternator would be bad out of the box. I know it's possible, but unlikely and the truck has the same sysmptoms as before the change. The battery has been changed as well. The truck is a 1993 Dodge 250 with an automatic. It has the Cummins Generation 1, 5.9L Six Turbo diesel in it.

Any help would be greatly appreciated.

Dave
 

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alt batt

ok so i have been finghting an issue similar to this as well. wire harness along the firewall was routed under heater hoses=wires touching manifold melted signal wire going to regulator as well as input wire coming from the alternator. I fixed wires, as the regulator, alternator, and battery are all brand new. So i eliminated the wire issue as my blower motor fuse kept blowing (i checked the blower motor, the fan speed control switch, then went under the hood and found the melted wires) I just ran a grabbed a regulator from advanced auto parts, still did not solve battery drain. Took to a local electrical shop and hooked it up= brand new regular was junk so i replaced it with one of theirs and BAAM problem solved holding right around 14V with headlights and heater on, ironically my radio no longer gets interferrence, my ebrake light and my abs light are no longer lit all the time. I hope you are able to figure this out I would take alternator off and have it tested and go from there.

Sorry for the long write up but I figured it might help others that might have the possible symptoms.

Good Luck
BTW my truck is an 89 W250
 

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Discussion Starter · #11 ·
Thanks for your reply, I appreciate it. I'm not sure what my next step is yet. I did check for burnt wires and fusable links. But, who knows, I might have missed one.

D
 

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Discussion Starter · #12 ·
Should I be getting voltage from the small connectors on the back of the alternator field windings? I just replaced the alternaor and I hate to take it off again, but it seems like it's not putting out any voltage.

Can anybody tell me how to check the alternator with a voltmeter correctly. I did read a previous post that said to put the meter on each small wire connection at the back. One should read 12 volts and the other nothing. Then ground one for charging, but I get no voltage at either post.

Anybody?
 

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Alternator is called that because voltage alternates.

Regulator/Rectifier is called that because it rectifies AC into DC. Then regulates it into 14V.

When measuring between alt and reg, switch meter to AC. Could be in the 30-40vac range above idle.

Mike
 

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Discussion Starter · #14 ·
Mike:

Boy, I should have known that. I'm used to having the rectifier/regulator built into the alternator. This whole thing is a bit foreign to me. Thanks for your help Mike. I will retest the alternator for alternating current readings. Hopefully, I can eliminate the alternator as a problem. I think if it works ok, I'm going to order a PCM. There are other symptoms that seem to point away from the CPS, crank positioning sensor and it looks ok, no broken wires etc.

Dave
 

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When measuring between alt and reg, switch meter to AC
That won't work. There is no externial AC from our alt's. That is internal to the diode pack only. Our regulators controll the ground of one field terminal. The other field terminal is supplied 12 volt DC power.

Our charging system is not supplied power till the engine is running. That is controlled by the PCM threw the ASD (auto shutdown) relay. So you will not have power with the key on at any field terminal

The ASD relay is mounted on the left inner fender well. It is the relay closest to the battery. If the PCM doesn't turn this relay on. Most likely it isn't getting a RPM signal or the relay might be bad.
 

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Sounds like your computer has died. They control a bunch of things including charging. Sadly they are not cheap. Old trucks like mine don't have them and use an external regulator like all older Dodges. Late production '91 to '93's have an ECM computer which does fail from time to time.
 

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That won't work. There is no externial AC from our alt's. That is internal to the diode pack only. Our regulators controll the ground of one field terminal. The other field terminal is supplied 12 volt DC power.

Our charging system is not supplied power till the engine is running. That is controlled by the PCM threw the ASD (auto shutdown) relay. So you will not have power with the key on at any field terminal

The ASD relay is mounted on the left inner fender well. It is the relay closest to the battery. If the PCM doesn't turn this relay on. Most likely it isn't getting a RPM signal or the relay might be bad.
Really?! That seems like kind of a shatty design... The diodes and rectifier transistors (or MOSFETs) are almost always the first thing to go... I can see having them both in the alternator for ease of "changing everything" (like Ford, GM, and pretty much everybody else), and I can see having an alternator and a seperate Reg/Rec, so you only have to replace the reg/rec when it dies, not the whole alternator, which is normally still good (like pretty much all motorcycles that have the alt on the engine, and the R/R on the subframe somewhere)...

It would seem that, with the Dodge design, you have the diodes in the alternator to fail, as well as the seperate regulator to fail? So you've got the hassle and complexity of having a seperate regulator, and the cost of still having to replace the alternator when the diodes go out... As an EE, that is a horrible design.

Mike
 

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Discussion Starter · #18 ·
Thanks all for your inputs. I am leaning towards the PCM too. But, is there any way to check the crank positioning sensor? Also, can I check the ASD relay? Because of the confusion for me on the design of the Alternator circuit itself, I've removed the new alternator and brought it back to Auto Zone where they checked it out. It passes and the technician put a multimeter on it while he was testing it to show that he was getting around 15 volts out of the unit too. So, I've eliminated that as a problem. The alternator is good and I suspect the old alternator was not the problem either. So, now that I'm a little more educated on the alternator and the rest of the charging system I really don't want to throw more money at this problem without checking parts. I hate to parts swap, especially when the PCM is around $400.

If you guys have any procedures to check the CPS and the ASD relay that would be great.

Thanks

Dave
 

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Discussion Starter · #20 ·
Philip:

Thanks for the information. I did see that write up. I will try to re-create it and see what I get. If I turn the crank over to an air gap and send 8 volts down the Tan/yellow wire I should get 5 volts out of the Gray/black sensor wire. Is that correct? How would I connect the Tan yellow wire to the 8 volt source? Would I put the possitive connection on the Tan yellow wire pin on the sensor and then put the negative connection where?

Thanks

Dave
 
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