Alt. not charging

[iangoround]

Hi all

Brand new 120A alt from Rock Auto. The power and ground feeds check out, but there is no voltage at the field wires. System voltage with the car running is 12.xx until the battery runs down. I had it down to 11.87 and the car was still running with no noticeable problems. Oops.

Tonight was supposed to be the night I broke the engine in properly, but then this came up.

Assuming no broken wires or unplugged connectors, what are the possible causes and solutions to this problem? Also, the check engine light is on but the only codes it throws are 12 and 55.

[iangoround]

So here is what I've found:

The alt power and ground lines are fine. The power module to alternator lines are fine. The logic module to power module lines are fine. The only problem I can find is that the logic module doesn't put out anything on the voltage regulation line when the car is running. Sometimes when the car is off it will put out between 5 and 8 volts, but as soon as I start the car is drops to 0.01 volts. I even popped it out of the case and checked the voltage at the pin on the circuit board itself.

Sounds like whatever drives the voltage regulator in the logic module died? There are no error codes though. I think the check engine light from before was the "flash CEL when knock" mod on the calibration I'm running. It went away after the lifters bled themselves out some and the pistons warmed up.

Has anyone successfully repaired the LM voltage regulator before? Or should I find a new LM or pop in an external regulator?

[turbovanman²]

The PM does all the work for the alt, so assuming all the powers and grounds check out, you need another PM or use an external voltage regulator. I don't think anyone has repaired the internal one due to PM"s being so cheap and plentiful but I guess that will change one day.

[neongary]

Not to hijack your thread, but can you provide a link or p/n for that new alternator? Been looking for a new 120 alternator, but didn't see one from Rock Auto.

[iangoround]

Not to hijack your thread, but can you provide a link or p/n for that new alternator? Been looking for a new 120 alternator, but didn't see one from Rock Auto.

Found it listed under 88 Shelby Z. Rock Auto P/N 1866010. 120a Beck/Arnley. Wholesaler closeout - 5 remaining. $41.99 with no core charge. 30 Day warranty.

The one I bought got shipped to me in its original box with very little packing material and the plastic cover plate was cracked from being banged around. I thought about sending it back, but its only cosmetic and it seems to work fine.

[iangoround]

The PM does all the work for the alt, so assuming all the powers and grounds check out, you need another PM or use an external voltage regulator. I don't think anyone has repaired the internal one due to PM"s being so cheap and plentiful but I guess that will change one day.

I know the PM does the actual work, but I think I meant to ask if anyone has tried repairing the part of the LM that tells the PM what to do. I suppose it doesn't matter.

I putzed with it a while tonight and found that the LM will send the PM around 5v in a key on/engine off state, but as soon as the engine is running it stops sending the regulation signal. I can't tell if the actual regulator circuit in the PM works or not as I don't have a handy way to send it the proper regulation signal with the car running. I tried another PM I found in the shed, but the car wouldn't even start with that one.

I also went junkyarding today looking for an external voltage reg and connector. The only thing I came up with was a 4-wire ford regulator off a 78 F150. I couldn't figure out how to adapt it though. I guess I'll buy a new dodge regulator and rig together some sort of connector temporarily until I can find a real one.

[turbovanman²]

Found it listed under 88 Shelby Z. Rock Auto P/N 1866010. 120a Beck/Arnley. Wholesaler closeout - 5 remaining. $41.99 with no core charge. 30 Day warranty.

The one I bought got shipped to me in its original box with very little packing material and the plastic cover plate was cracked from being banged around. I thought about sending it back, but its only cosmetic and it seems to work fine.

Bummer, too bad its a Bosch type unit, :(


I know the PM does the actual work, but I think I meant to ask if anyone has tried repairing the part of the LM that tells the PM what to do. I suppose it doesn't matter.

I putzed with it a while tonight and found that the LM will send the PM around 5v in a key on/engine off state, but as soon as the engine is running it stops sending the regulation signal. I can't tell if the actual regulator circuit in the PM works or not as I don't have a handy way to send it the proper regulation signal with the car running. I tried another PM I found in the shed, but the car wouldn't even start with that one.

I also went junkyarding today looking for an external voltage reg and connector. The only thing I came up with was a 4-wire ford regulator off a 78 F150. I couldn't figure out how to adapt it though. I guess I'll buy a new dodge regulator and rig together some sort of connector temporarily until I can find a real one.

Hmm, interesting.

What about just getting some or a resistor to knock the voltage down to 5 volts and apply it to the PM sense wire.

[Username]

This is what I did to my old GLH-S when the voltage regulator went out. Worked great, and if you want paint the VR black before you install it, so it won't stand out so much.
http://picasaweb.google.com/lh/photo/ZZXfeUO6k6x2JF5KAVaw-g?feat=directlink if that doesn't work, here's a linkhttp://picasaweb.google.com/lh/photo/ZZXfeUO6k6x2JF5KAVaw-g?feat=directlink

[turbovanman²]

Make sure you leave spot on the reg as it uses the case for a ground, :thumb:

[neongary]

Found it listed under 88 Shelby Z. Rock Auto P/N 1866010. 120a Beck/Arnley. Wholesaler closeout - 5 remaining. $41.99 with no core charge. 30 Day warranty.

The one I bought got shipped to me in its original box with very little packing material and the plastic cover plate was cracked from being banged around. I thought about sending it back, but its only cosmetic and it seems to work fine.
That's not a new unit....it's a reman.

[neongary]

Bummer, too bad its a Bosch type unit, :(
It's a Chrysler unit, not Bosch.

[iangoround]

So today I bought a dodge external regulator. I think the listing was for a 86 ramcharger or something. Got it wired in and I now have 14.78V at the battery! That seems a little high to me, but the battery is also probably pretty discharged so the regulator may be working overtime to bring the battery voltage up. I threw my charger on it and I'll start it up again later to see if the charge voltage goes down any. If not, is 14.7 too high or am I safe?

[prepared]

14.7 is stoic.

Oh wait, that's air/fuel not charging volts!!

14.7 is a little high. Not sure if it would be enough to damage a battery, but everything else SHOULD be fine.

[sdac guy]

So here is what I've found:

The alt power and ground lines are fine. The power module to alternator lines are fine. The logic module to power module lines are fine. The only problem I can find is that the logic module doesn't put out anything on the voltage regulation line when the car is running. Sometimes when the car is off it will put out between 5 and 8 volts, but as soon as I start the car is drops to 0.01 volts. I even popped it out of the case and checked the voltage at the pin on the circuit board itself.

Sounds like whatever drives the voltage regulator in the logic module died? There are no error codes though. I think the check engine light from before was the "flash CEL when knock" mod on the calibration I'm running. It went away after the lifters bled themselves out some and the pistons warmed up.

Has anyone successfully repaired the LM voltage regulator before? Or should I find a new LM or pop in an external regulator?

According to the Instructors Guide (and the FSM wiring diagrams) there should be 12v on one of the field wires anytime the ignition switch is in the run position. This is a direct connection from the ignition switch to the J2 power feed, to the alternator.

The power module adjusts the amount of ground that goes on the other field terminal lead via the built in voltage regulator.

If you don't have the 12v present on the alternator field coil when the ignition switch is in the run position it is not a voltage regulator or LM/PM problem. It is a wiring problem.

Barry

[turbovanman²]

It's a Chrysler unit, not Bosch.

Close enough, lol.


So today I bought a dodge external regulator. I think the listing was for a 86 ramcharger or something. Got it wired in and I now have 14.78V at the battery! That seems a little high to me, but the battery is also probably pretty discharged so the regulator may be working overtime to bring the battery voltage up. I threw my charger on it and I'll start it up again later to see if the charge voltage goes down any. If not, is 14.7 too high or am I safe?

That's fine.


According to the Instructors Guide (and the FSM wiring diagrams) there should be 12v on one of the field wires anytime the ignition switch is in the run position. This is a direct connection from the ignition switch to the J2 power feed, to the alternator.

The power module adjusts the amount of ground that goes on the other field terminal lead via the built in voltage regulator.

If you don't have the 12v present on the alternator field coil when the ignition switch is in the run position it is not a voltage regulator or LM/PM problem. It is a wiring problem.

Barry

Correct.

[iangoround]

According to the Instructors Guide (and the FSM wiring diagrams) there should be 12v on one of the field wires anytime the ignition switch is in the run position. This is a direct connection from the ignition switch to the J2 power feed, to the alternator.

The power module adjusts the amount of ground that goes on the other field terminal lead via the built in voltage regulator.

If you don't have the 12v present on the alternator field coil when the ignition switch is in the run position it is not a voltage regulator or LM/PM problem. It is a wiring problem.

Barry


Thanks for the info. If I remember what I was doing last night, there weren't any continuity problems I could find between the PM and alt. I might go back through and see if I can find the problem just for giggles, but at least for now it is running correctly on an external regulator.

If the charge voltage doesn't come down I'll double check to make sure the regulator is seeing true battery voltage off my J2 splice. I suppose 14.7 isn't terrible though...

[sdac guy]

Thanks for the info. If I remember what I was doing last night, there weren't any continuity problems I could find between the PM and alt. The problem will not be between the PM and alternator. The problem will be between the J2 power feed and the alternator. Just turn the key to the on position and see where the 12v ends on the J2 (why it doesn't make it to the alternator).

Barry

[iangoround]

The problem will not be between the PM and alternator. The problem will be between the J2 power feed and the alternator. Just turn the key to the on position and see where the 12v ends on the J2 (why it doesn't make it to the alternator).

Barry

There is/was 12v at the alt with the key on. Maybe I was over complicating things and I just have a PM with a bad regulator in it. To rig up the external regulator I tapped in to the J2 feed at the alt harness and moved the R3 pin from that connector to the external regulator.

It is still charging around 14.78v. I noticed there is about a 0.2v difference between battery voltage and the J2 feed at the external regulator. Could that account for the slightly higher charge?

I'm going to go through and clean all the connectors and re-apply dielectric grease. Perhaps that will change something, maybe not. Not a bad thing to do anyway on a 24 year old car I suppose.

I still can't figure out why the check engine light is on though. It only gives me code 12 and 55. I'll disable the CEL on knock in the cal first and see if it goes away, but I unplugged the knock sensor and it didn't seem to make a difference.

[sdac guy]

Hi all

Brand new 120A alt from Rock Auto. The power and ground feeds check out, but there is no voltage at the field wires. ....Okey dokey, I was going by this statement from your first post. In another post I thought you mentioned that you had 12v on the field wires with the switch on, but with the engine running you did not. Be sure that your ignition key is returning all the way to the run position after releasing it from start. I've had keys stuck in between positions and got flaky power problems from that.

Reading more from the "Instructor's Guide", there are a few conditions related to the alternator and charging circuit that will turn on the power loss lamp. Some of them set code 16 and some do not. Some conditions that set code 16 erase it when the key is turned off, and it says there are instances when the code cannot be read by a DRB (or other means?).

So, it sounds like the LM is recognizing there is a problem with the charging circuit and turning on the lamp.

Barry

[iangoround]

Okey dokey, I was going by this statement from your first post. In another post I thought you mentioned that you had 12v on the field wires with the switch on, but with the engine running you did not.

I think I initially tested it with the engine running. I did have 12v at the field terminals in a key on/engine off state last night. I think for giggles I'm going to go out and hook it back up to stock and see what happens.



Be sure that your ignition key is returning all the way to the run position after releasing it from start. I've had keys stuck in between positions and got flaky power problems from that.

I'll make sure to check that. This steering column is a wobbly tilt one, and I have had it apart in the past in an attempt to fix that. I may have put something back together wrong. The car has been garaged for a loooong time while I built this engine.



Reading more from the "Instructor's Guide", there are a few conditions related to the alternator and charging circuit that will turn on the power loss lamp. Some of them set code 16 and some do not. Some conditions that set code 16 erase it when the key is turned off, and it says there are instances when the code cannot be read by a DRB (or other means?).

Well that just plain isn't helpful at all. Would you mind scanning some of those pages so I can look at them?


So, it sounds like the LM is recognizing there is a problem with the charging circuit and turning on the lamp.


Barry

Well, I know that all of the wires going to and from the LM, PM, and alternator are good. I was thumbing through my FSM and came across a few test procedures. I don't have it in front of me right now but I think it said something along the lines of jumping power from somewhere to the voltage regulation signal line at the LM. If the voltage goes up, the problem is at the LM. If not, it's someplace else. I may try that and see what happens. I did accidentally forget to unhook the battery and computer when I was doing some welding on the passenger side floorpan...

[sdac guy]

Reading more from the "Instructor's Guide", there are a few conditions related to the alternator and charging circuit that will turn on the power loss lamp. Some of them set code 16 and some do not. Some conditions that set code 16 erase it when the key is turned off, and it says there are instances when the code cannot be read by a DRB (or other means?).

Well that just plain isn't helpful at all. Would you mind scanning some of those pages so I can look at them?

Yep, gotcha there. All I was trying to get across is that the charging circuit fault can set the lamp on, but not store a code that is readable.

It's only a few paragraphs to type, so I will give it a go.



Fault Code 16 (Open Circuit Voltage Sense Wire)
60 seconds after engine start-up, the logic module begins to monitor the voltage sense line for an open circuit. If after 60 seconds the voltage on the sense circuit is below 4 volts, the power loss/limited light is turned on. The system is now in "limp-in". Fault code 16 is stored in the logic module's memory. At this time the logic module will drive the alternator field at a 25% duty cycle to prevent overcharging and to get the car home.

If the voltage is between 4 and 8.5 volts, the logic module will full field the alternator for 20 seconds. If after the 20 seconds, the voltage is between 7.5 and 8.5 volts, the power loss/limited lamp is turned on. The system is now in "limp-in". Fault code 16 is stored in the logic module's memory, however it cannot be read using the diagnostic readout box. The alternator is driven at the "limp-in" duty cycle of 25%. If after 20 seconds of full fielding of the alternator, the the voltage comes up above 8.5 volts, the system reverts back to normal operation and the power loss/limited light is turned off.

The logic module is fed 12 volts (battery feed) from one wire (RD/WT) out of the power module. This wire divides at the J11 splice and feeds two different circuits in the logic module. One circuit is the voltage sense circuit. The second circuit is the volt feed for the second 5 volt regulator in the logic module. This regulator powers up the logic module's memory and keeps it powered up when the ignition key is "off". This also allows you to read fault codes. This second circuit is tied to the 8 volt feed to the logic module through a diode inside the logic module.

If the 12 volt feed circuit is open on the power side of the J11 splice, 8 volts will feed back through the diode in the logic module. This would put 8 volts on both circuits (voltage sense and memory) all the time. This is the reason for the 7.5 to 8.5 voltage "window" in the software. If the voltage doesn't come up after the alternator has been full fielded, the logic module assumes that the 12 volts feed is open on the power module side of the J11 splcie and the 8 volts present on the voltage sense circuit is not the actual charging system voltage. In this case the power loss/limited light is turned on, however; no fault code is stored in memory. This happens because, when the ignition key is turned "off" to start the diagnostic sequence, this shuts down the 8 volt regulator in the power module. This clears the logic module's memory because the 8 volts is the only thing keeping the logic module's memory "alive". If the engine is restarted, after 1 minute 20 seconds, the power loss/limited light will come back on again.

If the 12 volt feed from the power module is open on the logic module side of the J11 splice (voltage sense pin 2-22) the power loss/limited light is not turned on at all and there are no fault codes in memory.

Barry

[iangoround]

That's interesting. My CEL comes on immediately on start of the engine though. I suppose it could still be related...

I was just out messing with it and may have found the culprit. According to the diagnostic procedure in the FSM, jumping two pins on the LM should full field the alternator as long as the PM is good. I tried that and it didn't. I ohmed-out the control line from the LM to PM again and it showed as fine. So for now I'm going to assume the PM has a bad regulator in it. Pity the spare one I had doesn't work.

I will check the J11 splice as well. I'd much rather run the internal regulator if I can get away with it and save the room on the firewall, and hopefully turn off that stupid CEL.

[iangoround]

It doesn't appear to be a problem on the J11 circuit. I have battery voltage at both pins on that circuit at all times.

I'm fairly certain the regulator in the PM is bad, so I'll replace it when I can and see what happens. I do have to get the car inspected though, and I wonder what they'll say about the CEL being on...

[iangoround]

Zombie thread revivial!

I replaced the PM and the charging system now works as it should with about 14 volts under full load (lights, blower, etc all on high) BUT that damn CEL is still on. The car also doesn't want to idle until it's pretty warmed up and will sort of surge between 900 and 400 and most of the time just die unless you keep your foot on it. Its been so long since I've messed with it that I don't remember what calibration is in there at the moment. I think it might be a flavor of turbonator v9 or 10.

At this point I'm kind of stumped as to where to look next. I think I may see if I can hunt down some stock injectors and a 2 bar map to borrow for a while and set everything back as stock as I can get it and see if my problems are still there.

[turbovanman²]

Well the PM doesn't control the engine parameters so to speak.

What code are you getting?

[iangoround]

I couldn't get it to give me anything, not even 12 and 55.

I did notice that when the engine stumbles to the point of almost stalling the CEL goes out, but that might not mean anything.

[turbovanman²]

I couldn't get it to give me anything, not even 12 and 55.

I did notice that when the engine stumbles to the point of almost stalling the CEL goes out, but that might not mean anything.

Weird, can you borrow a scanner?

[iangoround]

I don't know anyone with a scanner, but the LM is set up for USB datalogging. Didn't someone make something I could put on a laptop and use? Time to dig though the EFI section!

[iangoround]

I MAY have found the problem.

Circuit N6 that is supposed to be an 8v supply to the LM is more like 12v at both the LM and PM plugs. There were two more oddities...K5 and N5 at the LM plug were registering 12v and 8v. The manual says those are supposed to be the ground from the fuel rail and the ground from some sensors. I left my sheet with which was which voltage in the garage, but it sounds like I either have some grounding problems or some crossed wires. Maybe that explains why the car can't idle worth a crap cold and runs super rich?

Maybe it's time to rip the whole engine bay harness out and rebuild it.

[Force Fed Mopar]

Moar zombie thread!

I'm having an annoying under-charging issue on the GLHT I bought also. Have tried 3 different alternators, 2 of which I am pretty sure are good. All wires are good. Am getting full battery voltage to the alternator field. Still no charge. Have tried a know good PM also, no change.

The voltage regulation wire from the LM (DG/OR tracer) is getting 9-9.5 volts at the PM connector while running, while battery voltage is 11.9. Isn't it supposed to have the same voltage as the battery?

Is it possible to ground the other field terminal to test if the alternator will put out proper voltage? Or will that cause it to overcharge to 18+v?

I have external regulators laying around, but would like to find the problem at least.

[turbovanman²]

The computer toggles voltage thru the field terminals to control the output, so if you want to check the alternator, you'll need to check voltage and amps, voltage alone won't cut it. Remove the field wires, then hook one a wire up to one field terminal on the alt to +, then start the car, put the other field terminal to ground and you should get full output of the alternator, IE 100 amps and 14-15 volts, if one isn't in spec, IE 100 amps but 11 volts, then your alt is bad, if yes, then you have a wiring issue or LM problem.

[MiniMopar]

Measure the voltage from the negative battery terminal to each of the big lugs on the alternator. The one that attaches to the pigtail from the hardness is the positive and the other is negative. I've had the ground splice in the front engine harness go on me.

[Force Fed Mopar]

Well I grounded the field out and it charged, hooked the harness back up and it is still charging?! I guess full fielding it jolted something into working.

[RoadWarrior222]

I'd presume there's a bad connection somewhere then. Just needed to blast through some oxide.

[jckrieger]

I'll revive the zombie thread once again. My 86 GLHS was charging intermittently. I first upgraded to the lighter weight Denso alternator, but still had the intermittent problem. I found a rebuild PM on Rock Auto and now the charging system seems to be working fine. This is the third PM/SMEC/SBEC where I've had the voltage regulator fail. On the SBEC I just wired an external regulator as suggested previously in the thread. I believe I had a persistent check engine light because of this though.

[iangoround]

I've seen two PMs with bad voltage regulators. For a while I was just running an external regulator and I disabled that engine code in MPTune.