Lancer Charging System

[86TSiGuy]

I've been on the "other" forum for years under same name, but I've read and researched here frequently. So "Hi" to the group for starters.

I need help saving an otherwise excellent condition 87' Lancer 4dr T1. Car started undercharging. No voltage between (+) on alt. and (-) batt. terminal. No voltage across field coil terminals. either field coil terminal to (-) batt. shows batt. voltage.

Voltage input sense line at LM shows batt. voltage. Voltage regulation line at LM shows no voltage.

I charge the batterieses ( tried x3 including one bought new ) on a trickle charger to 13-13.5 volts. Put them in and batt. voltage drops to 12.5 and then runs off slowly until eventually car dies.

Things I've tried;
(1) Swapped known good alt. no effect.
(2) Swapped known good battery no effect.
(3) Bought a donor harness and refurbished and tested alt. sub-harness, no effect.
(4) Replaced power module in fender, no effect.
(5) Wired in external voltage reg., no effect.
(6) Replaced all fusible links.
(7) Tested most grounds.

The volt. readings say it's a regulator issue, but I tried two brand new external regulators. I am sure they were wired and grounded appropriately.

At this point I'm so done putting money into this car that I'm going to scrap it. This would be a tremendous shame for a low mileage otherwise perfect TD.

Please help me save this lancer...

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Should EITHER field coil terminal read full batt. voltage (+12.5) when measured to ground?
I thought that one field coil was batt. voltage and the other was cycled to ground.
There is no voltage when read across both coil terminals.

[cordes]

Start here and report back if you still have a problem. It explains what you're looking for on the field terminals etc.

http://www.minimopar.net/charging.html

[86TSiGuy]

I've read and re-read the charging system info there more times than I care to re-count.
It isn't specific about getting voltage across either terminal only that there should be voltage across the two terminals or your not charging, which is of course what I'm experiencing.

I used the the wiring pin-outs on there to trace the voltage "sense" and "control lines" at the LM. I can confirm that the LM is getting the low batt. voltage and as such should be outputting voltage through the "control" line to the PM. It is not, voltage measured at the LM pin on the "control" line reads nearly zero.

So i figured I'd wire in an external regulator, unfortunately this has the same effect, zero charging.

Would somebody be willing to take one quick measurement for me on a correct running TD?
I need someone to measure the voltage between one field coil terminal and ground, then the other coil terminal and ground.

[Vigo]

Should EITHER field coil terminal read full batt. voltage (+12.5) when measured to ground?
I thought that one field coil was batt. voltage and the other was cycled to ground.
There is no voltage when read across both coil terminals.

ONE of the field terminals should show something roughly 5-10V. The other should show close to 0v because it is on the ground side of the circuit and the field coils should drop almost all the voltage, leaving only whatever voltage it takes to overcome the small resistance in the ground circuit. It should be well under 1v if the ground path is good.

The fact that you have full battery volts on BOTH means that the supply to the field coil is fine, but the ground side is not being switched. The ground side is open circuit right now.

I know you say you have tried two external regulators with no change and are sure they were wired correctly, but either both were dead on arrival, or it WASNT wired correctly. I just helped a friend diagnose a regulation issue on a Lancer i sold him. He put on an external reg and called to say it wasnt working. I asked him to check one thing, he fixed it, and now it works. In your case it may be that the external regulator's ground path is bad. Some of them ground through mounting screws, others tell you to just screw a ring terminal into some sheet metal near it. Either one is prone to having connection issues.. Is one of the externals still wired onto the car?

Regardless of what this situation may have led you to believe, the charging system is very simple and whatever is going on is a simple problem. You CAN fix it, so dont scrap the car!

[86TSiGuy]

I'm trying not to scrap it I swear.

Thank you for the definitive information.

I did run a line from one of the mounting holes on the ext. reg. to both a tested good chasis ground behind the battery as well as the battery negative terminal.

The ext. reg. is still wired in, It is connected in parallel with the stock alt. sub. harness. I did this with the reasoning that the +12V coil was getting full battery voltage so it was okay to use as the +12V switched source for the ext. reg. and the other coil must have failed into an "open" circuit if it was the culprit because I had no charging.

So the alt. sub. harness brings +12V to the lower field coil terminal and then I ran a 14 gauge wire from there to the lower (midle) pin of the ext. reg.

The left or (upper) terminal of the ext. reg. runs directly to the upper field coil terminal.

Both ext. reg. connections were made with a soldered eyelet placed on top of the alt. sub. harness connections under the hat-nuts.

To be clear: NO voltage across both field coil terminals but full voltage between each coil terminal and ground is what I'm seeing.

Would that not indicate that the ground coil terminal (upper on alt.) is is receiving batt. voltage instead of ground?

Tomorrow I will try bending the stock. alt. harness ground coil terminal tab up and out of the way and tape it off leaving only a known and tested good ground through the ext. reg. and see if this works.

Last thought, can I ground the upper field coil terminal to the body to see if will cause full duty cycle charging momentarily?

Keep the info coming, I know this charging system isn't complex that's why I'm so frustrated with being unable to understand what is going on. I think I've read every charging system thread on both sites and I can't find a similar issue.

[cordes]

No voltage between the two field coil studs indicates that they are at the same voltage. That's confirmed by the fact that they're both seeing battery voltage when tested individually.

[86TSiGuy]

No voltage between the two field coil studs indicates that they are at the same voltage. That's confirmed by the fact that they're both seeing battery voltage when tested individually.

^This makes sense. Thank you.

How should the external regulator be properly grounded?

[Vigo]

Would that not indicate that the ground coil terminal (upper on alt.) is is receiving batt. voltage instead of ground?

Well, the way it works is that when there's no current flow through a circuit, it has the same voltage everywhere. Voltage is similar to pressure in a water pipe. Whatever makes the pressure (in this case the battery) will just fill all the pipes up to full pressure, and then nothing will move until you open up a way for it to get out. So the voltage is coming in through one terminal, going through the field coil, and out the other terminal and out the wire to wherever that circuit dead ends (the end that would normally be pulsed to ground by the regulator) and all of that is at full voltage until the regulator grounds the circuit, and then the pressure will go down because it's being converted into movement. So it's not that both terminals are feeding voltage to the coil. It's still only coming in from one of them. You could verify this by taking the alternator harness off the alternator itself and checking voltage between each terminal and ground with the key on.

As for how the regulator should be wired.. what brand and model are you using?

[86TSiGuy]

Okay good explanation.

The reg. is a VR-125, it looks like all of the others I've seen. 3 mounting holes, 2 pins, etc.

This means that the problem has to be with the ext. reg. grounding correct?
If it were grounded properly this would give the grounded field coil terminal somewhere to displace the voltage from the live field coil line and I should have charging. It should also mean that I can leave the existing alt. sub harness attached to both field coil terminals as a failed "open" line should not impede flow through the ext. reg.

There is no additional ground pin on the ext. reg. it would seem all I can do is ground it through the case.
Is there a better way to do so, or a test I can perform to check proper grounding of the external regulator.

Thanks again for all the help everyone.

[Vigo]

Ok, so yes, that one grounds through the case, which means it will ground through the car body and into the battery through the little ground wire that goes from the battery to the body.

The simplest way to test it would be to take a jumper wire/cable, hook one end to the battery negative terminal, and just poke the case on the regulator with the other end and see if the alt starts charging.

If you cant get it to work by poking around with a ground wire on the case, you have to check everything else.

That regulator just needs an ignition-switched power input (so it only runs when the key is on) and to hook the other wire to the ground side of the alternator field coil.

Now, you CAN just get the regulator's switched power FROM the alternator field coil supply. So basically both of your wires would run to the two field coil posts on the alternator (the little studs with the ~7mm nuts). But if you do that, you have to know which is which! Remember, when there is no ground path, both terminals are going to show the same voltage and you cant tell which one is the supply, so you would want to take the harness off the alt and check voltage between those terminals and ground with the key on to see which one was the supply. If you were to hook those two wires up backwards, the thing would look like it was wired right but it would not work.

And yes, since your computer's internal regulator isnt doing anything, there's no harm in leaving the whole factory harness hooked up and just adding your ring terminal on top of it on the field terminal posts.

[86TSiGuy]

Okay, Results:

I first disconnected the alt. sub. harness from the alt. and with key on tested for voltage at each field coil terminal connection.
They were in fact reversed, the top field coil was getting full batt. voltage and the lower nothing.

So I reversed the ext. reg. connections appropriately, with the top field coil terminal wired to lower/middle pin on ext. reg.
No effect, voltage at battery was still 12.5, both coil terminals have batt. voltage to ground, no voltage across both terminals.

I then ran a jumper wire between neg. batt. terminal and ext. reg. case.
No effect, same results as above.

I then swapped in another battery that had been on the trickle charger at 2 amps for 2 days and repeated.
No effect, same results as above.

Still scratching my head here.

What do I try next?

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Can I jumper the ground side field coil terminal to a body ground or the neg. batt. terminal to test the theory that the ground side is open? This should cause momentary full charging correct? If I quickly disconnect the jumper would system damage from over voltage be likely?

I know that the alt. case ground is good as I replaced/tested the section in the alt. sub harness and then the section from the sub harness to the batt. terminal. But I have not verified the alt. positive line past the sub harness.
I guess I'm asking if the positive line from the alt. was failed "open" and the alt. could not pass voltage to the battery would that also prevent the field coils from functioning? Or would the field coils still cycle regardless?

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Update (yet again, sorry);
I got impatient and jumpered the ground field coil to the body ground behind the battery.
Voila Instant charging!

I reverified the ground wire from the mounting hole on the ext. reg. I then jumpered damn near everywhere on the case to ground, nothing.

So my LM won't output anything on the "voltage control" line to the PM, rendering the stock VR non-functional. Then I wired in not one but two external VR's and they won't cycle to ground. What the ...?

Is there a better ext. reg. to use that is more reliable?

[Vigo]

So it sounds like you found one problem (switched wires on the VR) but still have another one.

I got impatient and jumpered the ground field coil to the body ground behind the battery.
Voila Instant charging!

Good, you've ruled out almost everything at this point. I think you have a dead external regulator. Do you still have the 1st regulator you put on, or did you trade it back in on warranty to get the 2nd one?

[86TSiGuy]

So it sounds like you found one problem (switched wires on the VR) but still have another one.



Good, you've ruled out almost everything at this point. I think you have a dead external regulator. Do you still have the 1st regulator you put on, or did you trade it back in on warranty to get the 2nd one?

I wired the first one same way, when it didn't work I assumed I had the coil wires reversed, when that didn't help I assumed I blew it by mis-wiring and bought the 2nd. Now this second one doesn't work but I bent the flange on the side to try a different mounting location (drivers strut tower instead of rad cradle). So I don't think I can return it. I can get a 3rd (the parts guy is going to give me a look), but I swear if this one's DOA I'll snap...lol

Possible my electrical system is killing them? Or are they really fragile/sensitive?

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Wow, I'm I thought I was confused before.
Put in a 3rd ext. reg. and woohoo system charging between 14 and 14.2 volts!

Here's the kicker;
The car runs terribly! It sounds like its missing on all cylinders, the idle is swinging between 1500 and 300 rpm.
The IAC is howling, full open trying to keep the engine running, exhaust smells rich, lots of thunderous backfiring.

Turn the car off, disconnect plug from external regulator, start car and it purrs at a nice constant 800 rpm.

Why would a car that ran great before the charging issue, that runs great on zero charging and 12.5 volts, run so terribly on 14 volts.

I disconnected the neg batt. terminal for 30 seconds to reset the computer, same result. I'm going to pull codes and check for a power loss light now.

Ideas? Anyone...

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Final update. Solved!Thank you everyone for the help.

[cordes]

Well, what was it?

[86TSiGuy]

Honestly, can't say for sure.

I pulled the battery in favor of the newest one.
I swapped the newer power module for the original.
I moved the ground lead from the ext. reg. from the common chassis ground behind the battery to one of the relay mounting screws on the fender well, and I jiggled damn near every wire, connection, and pig-tail in the engine bay.

Turned it over and it ran great again while charging. 14.4 volts at idle no load,
and 13.8 volts with everything on.

I guess I killed both ext. reg's by wiring them in field coils reversed.
The rough running could have been anything I swapped out.

[Vigo]

Damn, who cares at this point, sounds like it's time to stop the brain-wracking and just enjoy it for a while! Congrats!