Alternator troubles

[Duluth Diesel]

1993 Cummins 1-ton dually 4x4 with manual trans. Check engine light came on and voltage was about 9 volts. Radio and other electrical accessories stopped working. Limped the truck home since it kept running fine. Must have had just enough voltage to keep the shutoff solenoid from slamming shut.



So, we replaced the alternator and charged up the battery (which is fairly new). The truck starts and all things work (radio, wipers, etc) again.



Check engine light is still on.



Voltage meter is on the very low end of normal range.



Any thoughts? Parts I need to replace next? How do I make the CEL go away?



Any help is much apprecialted!



-Chuck

 

[JFaughn]

Chuck
One of the most comin , is a bad connection some where , the charging system uses the computer as a voltage regulator [ I thinks this is a dodge BS thing ]
Going by memory , there are 3 connections on the alt. large wire to battery , 2 small connectors , one to ground - in computer , other to power + battery , as the computer sees the need [ draw or low battery voltage ] and then increases the ground connections as demanded .
So to fix this , like any thing I like to do maintenance to avoid future issues and many times helps to find problems , in this case , disconnect all battery connections clean & put a battery preventive chemical on them , check fusable links [ a test lite & a little tug { if there is give , the wire inside can be bad with just the insulation holding }] then check the smaller wires at alt , dielectric grease on all connections [ makes them more resistant to developing a bad connection { should be done when the truck was built }] use a multi meter to check for power on either of the small wires [ not sure witch with out a diagram ] but one should have power & the other [ coming from computer should have some ground/resistance .
The regulating part of the computer almost never goes bad .
Some times while changing oil , a tool or something can bump/touch a wire on back of alt & blow fuse .
Good source .
LarryB's Dodge starting problems solved here.

 

[dpuckett]

Jfaughn- I beg to differ on the regulating part of the PCM rarely going bad- I've had it happen, as have a few other members.



BUT, before condemning the PCM, check voltage output with a voltmeter- my gauge doesnt read accurately 75% of the time. If the radio and other stuff quit, it could be a ground issue, or the regulator. Or something else entirely.



Start cheap and work your way up to the more expensive stuff. External voltage regulators that bypass the PCM have been done. My CEL was still on, but I think that is the only thing on the CEL circuit. Bulb removal made the light go out.



Daniel

 

[Duluth Diesel]

It all worked fine until the alternator died. Now since the alternator replacement, these problems are surfacing. We'll check all connections.



Does the CEL turn off as soon as the problem is fixed or do these old '93 trucks still display the CEL after the problem has been addressed? Do codes need to be cleared or is this truck to old for that complexity?

 

[JFaughn]

Did you check for what codes were there ?
May lead you to your problem .
They keep changing things , that truck is old enough to disconnect battery for 10 sec. to clear , newer trucks require a scanner to clear codes .
There 2 kind of codes hard & soft codes , soft codes only lite the CEL while the problem is happening , hard codes stay on weather the problem goes away or not , have to be cleared , soft codes will stay in memory till cleared .

 

[GIT-R-DONE]

Try runnig a ground from your negative battery to the cab and see if that helps, jumper cables would help out with this for the test.

 

[Philip]

Check the gap on the crank sensor. If the PCM does not see engine RPM it will not turn on the charging system. Gap should be around . 050" or so.



Check the 2 wire plug by #1 valve cover. See if the terminals are corrided or loose. Check it for broken wires also. That plug is for the crank sensor.

 

[JGrefenstette]

chuck,

i have a 93 250 getrag. i recently had the exact same problem you are having. i mean EXACT. i replaced the alt. and charged the battery. voltage was reading super low (truck was living off the battery still), so i took the alternator back to advance to have them check it. and it acctualy was only cranking at 10 amps. so i thought problem solved, i got a good one, had em check it and slapped it in. but the symptoms stayed the same. my dad found a post on here that lead the problem to the ECM. So we got a factory reman for around $130 after the core. after we put it in, the voltage gauge reads on the heavy side of streight up, and the other day, i was running, A/C, wippers, headlights, radio, and it was still reading a good voltage.





hope this helps

 

[Duluth Diesel]

Thanks for all the help! We're working on trying these solutions. Hopefully something works out.



-Chuck

 

[bflood]

My alternator quits when the outside temp gets hot #@$%!. Ya know, just when you need to be enjoying the A/C. It works just fine the rest of the time, even when I'm pulling a trailer at night with extra lights.



Been doing this for years now but I've moved to N. C. (from CT) and gotta fix it. I was going to get a new alternator but after reading this thread I see I've got some checking to do. Thanks.



If anyone has a temp related alternator problem like me and has more ideas, please contribute them

 

[JFaughn]

bflood , some yrs have a temp sensor under the battery , do some checking so that you know if its there , then what the resistance values should be for what temps .

 

[bflood]

This is a 93 and from reading the threads its shouldn't have a temp sensor. Also, I have the factory shop manual and it doesn't mention it.



New INFO: Had to haul a farm tractor today and predictably, the alternator crapped out. When I got home I left it running and put a voltmeter on the battery. Was reading 12. 2-12. 4. Next, I sprayed a water mist on the PCM for cooling. In a short while the alternator started charging and my voltmeter was reading 13. 7. Direct cause and effect.



If I assume (often a bad choice) that nothing is repairable in the PCM than I guess I should replace it.



BTW, This temp/charging thing is not ususally just on/off. I have a battery voltmeter on my dash (part of a compass gadget) and I usually can see the charging fade as the temperature gets near 102 degrees F in the engine compartment (yes, I have a temp sensor there as part of the compass gadget). I suspect a temperature mode failure in a solid state component of the generator (thats what the manual call this alternator) field control part of the PCM.



Thanks, and Suggestions always welcomed!!

 

[JFaughn]

I would say that spraying water is a BIG NO NO , that will make it bad for sure , I do know what your trying to do , I bought a tool that plugs into compressed air hose , and you get frosty cold air out of one end & very hot out the other , testing electrical , hot fail cool works .

 

[JFaughn]

Where did Chuck go ?

 

[cerberusiam]

BTW, This temp/charging thing is not ususally just on/off. I have a battery voltmeter on my dash (part of a compass gadget) and I usually can see the charging fade as the temperature gets near 102 degrees F in the engine compartment (yes, I have a temp sensor there as part of the compass gadget). I suspect a temperature mode failure in a solid state component of the generator (thats what the manual call this alternator) field control part of the PCM.



Thanks, and Suggestions always welcomed!!

Time for a new PCM. There is either a crack in the board/solder joint that is pulling apart when heated or a bad resistor/diode that is not operating within its temp range.

 

[Duluth Diesel]

2 alternators installed. Both were remanufactured and tested bad. Third time was the charm, and she has power again. Also found some questionable grounds and fixed them. During all the crawling around, we found a worn steering shaft and ordered a Borgesen unit to replace that as well. Thanks for all you help, guys!



-Chuck

 

[JFaughn]

Makes it hard when there are so many bad parts out there , I ordered a new one from Larry Bs ,

 

[Leper]

. There is either a crack in the board/solder joint that is pulling apart when heated or a bad resistor/diode that is not operating within its temp range.

Just a little FYI



On heat related failures like this, you can possibly fix it yourself. Many many times I have fixed radios, amps, fuel main relays(Honds cars), and others PCB (printed circuit boards) with a small tip soldering iron. Before I had Lasik done, I didn't even need a magnifying glass. Now I use an 8x glass. If you look over the back side of the pcb you may see what looks like a tiny hair on a solder joint. It is a break. Most times all you have to do is touch the spot with a tinned soldering iron tip and it will be fixed. I normally hit 5 to 10 joints around the area, if they are accessable without the possibility of hitting two at once.



**NOTE** I am assuming that if you try this that you are already aware of the dangers of electrostatic discharge and have grounded you and the component properly. A teeny tiny spark can ruin elaborate boards.





Just an option.

 

[dpuckett]

IIRC, Our PCms have the PCB, then it is encased in some sort of stuff that hardened and makes circuits unaccessible.



God advice on grounding yourself. I worked at a plant tha tmade PCBs and they stressed repeatedly grounding yourself and not making any static discharge. Apparently, the human body is capable of several thousand volts of electricity.



DP

 

[Nordby]

For a cheaper fix - use an external regulator and bypass the PCM. You will bypass any CPS problems as well. Some folks use a reg from a 1989 W250, I'm using one in my repowered Ford truck from a 1985 dodge pickup. Part numbers and wiring are near the end of my conversion thread.

If you have a nice first gen, probably worth the money to put a pcm in it. But, if your old truck resembles mine and is ranched out, has less paint than most vehicles' left front fender, and the doors sag, a cheaper fix sometimes is a better way to spend $$$'s.

jon.