Mechanics

GRAND 3.3 CODE 41 CHARGING SYSTEM CIRCUIT NOT RESPONDING TO CONTROL SIGNAL

1995 Plymouth Voyager • 138,000 miles

Battery is good and a new alternator has been installed, original did check bad. As soon as new alternator was installed, started the engine and dash voltage was reading 11 - 12. Drove it to parts place, they verified not charging. Drove back to house to replace the new one, son unhooked battery and it stayed running, I checked the dash and it read charging 13 - 14. A few hours later it wasn't again still setting in the drive. Unhooked battery cable while engine running and it immediately died. I can't find anything wrong, what do you suggest. Parts house has no suggestion, besides taking the new one off to replace, but after off and it checks good on their system, they won't replace it. I would gladly donate for help, but the new alternator took what I have at the moment.
Avatar
ET
December 9, 2011.



If the alt is good and charging at times and not others, make sure all wiring to it is in good condition, tight, and clean. Same with the battery wiring. If that all looks good, check the fuseable link between the battery and the alt. It may be in the process of going bad. If it is, the alt can't charge the battery.


Where is the fuseable link, nothing I have shows a fuseable link.


Tiny
ET
Dec 9, 2011.
See attached


Hi guys. Excuse me but I have to stick my nose in here and tell you to NEVER EVER disconnect the battery while the engine is running. That was a trick done many years ago by mechanics who didn't understand how these simple systems work. The battery is the key component in maintaining system voltage to a safe level. The voltage regulator can't do it by itself. Without the battery in the circuit, if the alternator is working and you raise engine speed, system voltage can easily exceed 30 volts and destroy every computer on your van and the diodes inside the alternator. I did that every year, on an alternator test bench, to prove to my students how dangerous doing that is. My '95 Grand Caravan has an Engine Computer, Body Computer, anti-lock brake computer, and automatic Transmission Computer, along with the radio and instrument cluster which could also be damaged. That's a huge potential repair bill and not worth the risk.

As for the fusible link Jacobandnickolas mentioned, it's plugged into the smaller positive battery cable. If it's bad, you'll find a higher voltage, (possibly as high as 30 volts) on the alternator's output terminal, but closer to 12 volts on the battery, while the engine is running. You should also measure full battery voltage on the alternator's output terminal with the engine off, but that's only a valuable test for a hard defect that's always there. For an intermittent problem like yours, that test is of no value and it won't be accurate because every strand of wire could be corroded apart but as long as there's a hint of carbon-tracking or corrosion in there, the voltmeter will pick that up and incorrectly show a good circuit. There's no way the alternator's 90 amps is going to get through that corrosion though.

A common intermittent problem is a corroded connector pin between the alternator and the voltage regulator which lives in the Engine Computer. The voltage regulator circuit is extremely reliable and trouble-free so the computer should be the very last thing to suspect.

Along with that voltage on the alternator's output terminal, all diagnostics can be done by measuring the two voltages on the two smaller wires. They're held on with two small nuts holding tabs coming out of a small black plastic block. Those two voltages must be measured with the engine running. One will have full battery voltage. The other one must have less but not 0 volts. Be aware a lot of incorrect "0 volts" are read due to those nuts being rusty so be sure your meter probes are making good contact. 0 volts on the second terminal means the brushes are worn. That always starts out as an intermittent problem and is most likely what happened to yours. I just changed them on my alternator for nine bucks a few weeks ago. If you read exactly the same voltage on both small wires, there's a break in the wire going to the Engine Computer / voltage regulator. If you find somewhere between 4 - 11 volts on the second wire, that entire circuit is working. If it still isn't charging, the problem is in the output side of the alternator or that fat wire going back to the battery.

I broke a lot of brushes to create "bugs" that I could switch in and out for my students to diagnose, and after the first '91 - 95 Caravan, I proved those brushes could be replaced without removing the alternator from the engine, at least with the 3.3L engine. Should you ever run into this again, I can post photos of the procedure.

Oh, one more observation. Your fault code 41 is only set when no current is flowing through the brushes and voltage regulator. If the defect is in the diodes or any other part of the alternator's output circuit or wiring, no code will be set even though the charging system isn't working. There's the low-current input side that creates the magnetic field, and the high-current output side that the charging current is "induced" in. The computer only monitors the low-current side.


Caradiodoc
Dec 10, 2011.
The alternator is new so no worn brushes but I plan to test everything else that you suggested. Thanks for the information.


Tiny
ET
Dec 10, 2011.
I don't know how I would be, but unless I'm checking the output from the alternator incorrectly. There is no output from any of the three areas you suggested me to check at the alternator with the engine running. The battery reads between 11 & 12 volts.


Tiny
ET
Dec 10, 2011.
You'd have to have two totally different unrelated problems if you're not seeing voltage on the output terminal AND either of the smaller wires.

Be sure your test light's ground clip or voltmeter's probe is on the battery negative cable, then touch the other probe to the positive cable. If you measure 12 volts or the test light lights up, you'll know the ground on the negative post is making good contact. Now move the probe from the positive post to the large output wire bolted to the back of the alternator. If you don't find voltage there, scratch the probe on the nut in case there's some rust on it. If there's a protective rubber cap on that wire, you have to push it aside. (Sorry for stating the obvious, but I did run into someone once who didn't understand you can't measure through an insulator).

The voltage on the smaller alternator wires comes from the automatic shutdown (ASD) relay. That relay also feeds the coil pack, injectors, oxygen sensor heaters, and fuel pump. We know that relay is working because the engine runs. Only two things then will prevent you from finding voltage on at least one of those small wires. There's a break in that wire, or more likely a corroded splice where it connects to the wire going to the coil and injectors, or there's a thick coating of rust on the nuts and your probe isn't cutting through it to make a good contact. I recently replaced the brushes on my '88 Grand Caravan and had a miserable time getting a reading with my voltmeter, and then to verify the open circuit with my ohm meter. I kept finding no voltage on the second wire, indicating worn brushes, but I also kept finding 0 volts on the feed wire leading me to the wrong conclusion. It wasn't until I finally removed those nuts and measured right on the shiny studs that I had confidence in my readings. I REALLY had confidence I had found the problem after I unbolted the brush assembly and found one of them completely gone!

If you still don't find voltage anywhere on the alternator, move the positive probe to the dark green / orange wire in the coil pack connector or any injector to check for voltage. Again, this must be done with the engine running. Back-probe through the connector's rubber seal by sliding the probe right alongside the wire until it goes in about a half inch and touches the terminal. We know there HAS to be voltage there, otherwise the engine wouldn't be running. If you don't find voltage, something is wrong with the way you're testing or with the connections. If you DO find voltage there but still not at any alternator terminal, scratch like a chicken on the nuts to be sure rust isn't preventing a good connection.


Caradiodoc
Dec 10, 2011.
The alternator is new and the new nuts came with it, although I have actually touched the positive probe to the stud that has the nut around it. Wouldn't the coil pack, injectors and so on continue to work off the battery power, that is until it's too low as it was when the vehicle died on me on the way to work the other day? I will retest trying to use the same ground with battery and the 3 different connections on the alternator. What about unhooking the wires going to the alternator and testing the 3 spots of it, could the wires themselves or what they connect to cause a dead short so nothing shows when testing? Also to update, the only time this new alternator has shown charging on the dash gauge, is the one time mentioned in the original message. Maybe it is actually a bad (new) alternator? Sorry for going in so many directions but I am at a loss and it is cold outside. : )


Tiny
ET
Dec 10, 2011.
The ground was my first problem. I found a place on the alternator bracket that I used to see the battery had power. The main wire to the battery and the closest to it (small stud)shows output while the motor is running but the other didn't move the hand of the volt meter at all. From your above that would say worn brushes (even though new alternator). All of this testing isn't accurate due to my volt meter. I have realized it only has settings for 10, 250 & 500. (I guess mainly for AC, batteries and ohms) I guess I have been wasting your time. Going to see if I can find and borrow a better volt meter to accurately do your tests.


Tiny
ET
Dec 10, 2011.
I'm in Wisconsin, and I agree, it's cold, darn it!

You're right about the coil and injectors running on battery power until it goes dead, but one of the small alternator wires is connected to the same wire so it has to have voltage at the same time unless there's a break in it after the splice. That entire circuit only has voltage with the engine running.

The fat output wire bolted to the alternator must have voltage all the time, engine running or not. If it doesn't, there is a break in that wire between the alternator and battery positive terminal. I can't remember if it is bolted to the under-hood fuse box or if it goes straight to the battery. When I get brave enough to go outside, I'll pop the hood on my '95 and look. When large wires are bolted to a stud on the fuse box, it is real common for them to work loose and arc or burn a ring around that stud and make an intermittent connection. More commonly that causes everything in the van to be intermittently dead, along with a no-start condition, but it depends which connection is loose. There's usually two studs with cables.


Caradiodoc
Dec 10, 2011.
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