Our Cummins powered RV 5.9 liter 6 cyl. has a (one wire) alternator wire problem.There are two wires on a connector going to the side of the alternator.The wire going to Pin 2 is a small loop of wire connecting Pin 2 to the main positive charging lug on the alternator.I assume that this is to energize the electromagnets...The second wire we thought would be the battery condition sensor wire... but when we check it for a good connection to the battery post area, we find 540 ohms of resistance.We also see that this Pin1 wire has a small load or resistance which would need to be tracked down and examined. So it appears as though this Pin 1 wire must go through some other connected devices / computer etc.As a result the twice changed new alternator is havng difficulty knowing how hard to be charging.Could you send me a schematic and some suggestions on where I could locate the root cause of the problem? Thanks, Mark
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Welcome to just answer.com. I'm here to help you and your 100% satisfaction is my goal.Both of these wires go back to the PC M to control the alternator
Am I able to send you jpeg photo images?The schematics show the Pin 1 wire going to the Powertrain Control Module for what appears to be a Pickup Truck. (based upon the location notes for grounds and modules. This RV is a 1999 Fleetwood Bounder Pusher.The wire colors indicated on the schematic do not match what I have; both wires on the side connector plug are red... as I mentioned, Pin 2 original harness has a second jumper wire 3 inches long -going to a ring terminal on the back of the alternator. This jumper wire ring terminal has been connected to the main power output teminal/lug on the back of the alternator... but there is another small lug (in addition to the ground connection) on the back of the alternator that has nothing connected to it. The ring terminal seems oversized for the small lug.I have looked for the powertrain Control Module and I don't see it in the engine compartment area. Most harness wires are heading toward the front of the RV along the chassis frame (driver's side). Would it be by the shifter?I will be looking through my manual to hopefully find a chassis wiring schematic as I await your reply to my questions on PCM location, ability to receive pictures, lugs on the alternator's back to be used or left without wires, schematic color mismatch etc.Mark
Yes send me a picture just attach it to your reply
I found some large plotted drawings of the Freightliner Chassis wiring.It shows the red wire colors correctly and that the connection of the jumper wire does rightly go to the large alternator power output lug. I'll try to take a picture of the plans as well. Are you the right guy to advise me on Freightliner RV wiring?
What is your vehicle identification number
You should have five pics attached. Schematics and actual viewsThe Pin 1 wire is called 1020B and goes through a diode, then to a connection where one of two wires named 1019 A goes to the ignition switchthe second wire 1019B goes to the ECM key switchThanks GregI hope you can tell me a bit about the charging irregularities. Originally with the first new alternator, the voltage would be normal then when the engine was rev'd up it would jump instantly to 18+volts... with headlights and heater on to reduce it as much as possible.The second, rebuilt alternator was also charging too much and pushing the voltage up above 16 volts. (like I said, there was 540 ohms between pin1 and the engine battery)
No none of the pictures came through please try again attach them using the paper clip icon at the top of your toolbar
Very good pictures apparently the camper company is using Just any old General Motors internal regulator alternator . The one wire gets looked around back to the back of the alternator to the large lug the other wire receives power to excite the field coils and begin the charging
So based upon the info and the schematics I sent you and in light of the overvoltage charging if the side connector is attached to PIN 1 and 2... What do you think I need to check on the wiring?Where should I be doing continuity checks? ECM? where/what is it?Ignition switch? does it send power in the start or run position?
Terminal 2 on the alt gets hooked to the battery feed wire and terminal 1 should be attached to a key on hot wire
I await your reply to my questions on the ECM keyswitch and its location. and your thoughts on the 540 ohms and the over voltage charging problem causes.If you want, relax until I reverify what we have found on the RV.I guess I was wrong about the which wire was a sensor wire and which energized the electromagnets. I will re-examine and re-tests by checking the ignition switch, and other wiring with jumpers bypasses if necessary. It won't be done until this Monday. I could use some help identifying parts... If no energizing 12 V is found at the alternator's Pin 1, I guess I have to pull the dash apart to get to the ign. wires.
Any overcharging would be a problem with the alternator itself make sure the case of the alternator is grounded properly, in the wires are hooked up in fashion I explained if the overcharges at that point this is an internal problem with the regulator in the alt
What EC M key switch are you referring to like to find
This is the second alternator. In the previous email in which the schematic pics didn't attach I wrote: The Pin 1 wire is called 1020B and goes through a diode, then to a connection where one of two wires named 1019 A goes to the ignition switch, from the same connection pointthe second wire 1019B goes to the ECM key switch.I don't know much about the ECM key switch other than it is on the schematic, and has another wire called N99 WHT.The alternators are from a rebuild shop. One was "new" and had the voltage jump / peg when the engine rpm was higher. The second alternator installed was the rebuilt original and its charge problem was an overcharge at a lower voltage. In playing with jumper wires the rebuilt would charge differently/correctlyI will try running a jumper wire from pin 2 to the battery to verify the alternator-regulator's ability to sense the battery condition... and verify the energizing voltage from the ignition switch to activate the electromagnets.
Try what I said run number one To an ignition key switch 12v volt hot wire
Attach number 2 to the big heavy feed wire on the back of the alternator ,Making sure the feed wire is in good condition going back to the Battery
Run an additional ground wire to the case of the alternator
And tell me what your output voltage is then
Hello Greg,In rechecking things, I found 7 ohms of resistance between the connector Pin 2 and the battery.The Alternator Pin 1 had 10.36 volts coming from the Ignition Switch which had 11.4 volts.There was a .3 volt drop across the ignition switch.Once the engine started and the connector contact cleaned, The alternator charged fine at 14 volts. Pin 1 voltage rose to 13 .4.Likewise, The ingnition switch was up and the voltage drop across the contacts went down. I don't know what changed to make things work now... but its working. Thanks for your help.
Very good you're welcome
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