charging problem with 93 dodge spirit - voltage regulator?

93 dodge spirit 220K miles

My Check engine light came on and the voltage indicator looked low
(10-12V). Fault codes wer 12, 17 (fixed by replacing thermostat), and
41. Checked the alternator (it was bad), replaced it and took a test
drive. So far so good.

The next day , the check engine light came back on and the charge
dropped back to 11. Pulled the alternator back out and had it checked
(it was good). Replaced the alternator belt. Problem went away.
Three miles down the road, the problem returned (I checked the belt
tension when I got to work and it seemed OK)

Next step - voltage regulator?
The consensus seems to be that the voltage regualtor lives in the
computer, but how do I verify (the Bosch replacement alternator didn't
have a sticker on it labeling it as externally regulated). Also, the
alternator has 5 connections (3 large posts and 2 small). I assume the
large posts are B+ and field connections? What are the 2 small posts?

Thanks for any help - I'll be the first to admit I don't really know
what I'm doing.

 

If the computer-integrated regulator is bad, it will set a code. It may
even be the 41 that you got.

If the regulator is bad, the problem can be fixed by installing an
external regulator. Dan Stern posted the procedure in this NG just last
week. A search of this NG should find it.

-Kirk Matheson

 

Yep, it'll be the 41 he got.

I keep that text on "speed dial".

 

One thing to check is the battery connections. They can cause a lot
of weird problems when the connection isn't quite good enough. A lot
of the problems they cause don't make sense, and it's very hard to
figure out how a battery connection could cause such problems.

One way to check the connection is to turn on the headlights and
measure the voltage between the battery post and the cable terminal
which is attached to that post. That voltage should be zero. If you
can measure even a fraction of a volt, the connection is bad.

When my battery connections were bad, I fixed them by cleaning the
insides of the cable terminals, where they wrap around the posts, with
fine sandpaper, and replacing the bolts that tighten the terminals,
because those bolts were ruined by age and corrosion.

 

The voltage between post and terminal is 0.000 Volts. Voltage between
+Post and B+ is 0.035V with headlights on. I know there should be some
potential drop across the wire to the B+ terminal, but how much?

Also, the harness that attaches to the alternator has 5 leads, the wo
smallest attach out of a black plastic 3"x2" cartridge looking thing.
Anybody know what purpose this serves?

Thanks,
Frank

 

Found D. Stern's post, which also explained the two small studs.
Off we go.

 

Sorry for the string of posts.
After some poking around with a voltmeter and reading D. Stern's post
several times, I've identified the two field terminals, and have two
ground studs handy on the alternator itself.

(sheepishly): Does the connection between (new) regulator base and
battery neg need to go all the way back to the battery, or can I use
one of the ground studs on the alternator?

Thanks for all the help,
Frank

 

Yep, next step voltage regulator. I post the facts and fix on this
issue about once a month.

Correct, the voltage regulator is in the SBEC (Single Board Engine
Controller).

Nope, the shielded large one is B+ and the unshielded one is case
ground. The two small ones are fields.

This voltage regulation issue is the most common SMEC/SBEC failure
(which is not to say it's very common; Chrysler's modules tend to be
pretty durable-just that this particular failure is usually how they
fail.) The official fix is to replace the SMEC/SBEC.

Here is a much less costly fix that *will* work, without replacing the
engine computer and without causing any additional problems:

First, pick one of the following regulators:

Regular normal electromechanical regulator:
NAPA Echlin VR32

Extra heavy duty electromechanical regulator w/vibrationproof mount:
NAPA Echlin VR34

Extra heavy duty electromechanical regulator w/vibrationproof mount and
convenient external voltage adjustment screw:
NAPA Echlin VR35, Standard-Bluestreak VR106

Transistorized regulator with no moving parts (no adjusting screw):
Standard-Bluestreak VR101, Wells VR706 (the wells item is very
inexpensive; it works but Wells doesn't make my favourite stuff)

Waterproof potted IC regulator with no moving parts (no adjusting
screw):
NAPA Echlin VR1001, Standard-Bluestreak VR128

Any of these regulators will have two terminals on it, one marked "IGN"
and the other marked "FLD". (the VR1001 and VR128 have the "fld"
terminal on the end of a short wire lead). The alternator gets the
original field wires removed from its two field terminals (right next
to each other, small studs with nuts retaining the two flag terminals
-- be careful not to break off the studs!).

The regulator IGN terminal gets 12V via the ignition switch, and the
"FLD" terminal gets connected via a wire to one (either) of the field
terminal studs on the alternator. The other field terminal on the
alternator gets connected via a wire to ground. Run a ground
wire-16ga is plenty-between the regulator base and the battery
negative terminal, and mount the regulator such that it won't rock 'n'
roll around. At this point, your charging system will once again work
fine. If you got the adjustable regulator, set it for 14.2v across the
battery with the engine fully warmed up and idling, no lamps or other
accessories on, and ambient temperature above 50°F.

Your "Check Engine" light will probably come on in response to this
fix, because the SBEC does not see itself as able to control the
voltage (right, it can't, because that's now the job of the new
regulator you just finished installing!) To silence the spurious
warning, put a resistor across the two original field wires that you
removed from the alternator, before securing these wires such that they
can't ground out or get caught in any moving parts.

Close the hood; you're done.

DS

 

Ground stud on alternator is fine.

 

Hmm. Connected the new voltage regulator, and the charge to the
battery is still low.
Here's what I did:
1. Mounted the new regulator to one of the ignition coil mounting
screws, which made both a secure mount and a good ground (I checked the
resistance).
2. I connected the wire formerly connected to the top field post to the
IGN stud (this is the same wire with 11.5 V when the car is running)
3. connected the FLD stud on the voltage regulator to the bottom field
post of the alternator.
4. Left the B+ wire connected to the large shielded connector on the
alternator
5. Connected the other field post and the 4th wire in the harness to
one of the bolts in the body of the alternator (the 4th wire was
formerly connected to the alternaotr body).
6. Reconnected the battery neg post and started the car.
I have not connected the resistor yet between the wires formerly
connected tot he filed posts, but from the previouis posts, it seems
like this would only affect the check engine light, not the actual
charge to the battery, yes?

Anything I'm doing worng?

 

No. The wires formerly connected to the alternator's two field studs DO
NOT get connected to the new regulator. Follow the directions in my
original post:

Run a NEW wire from ignition-switched +12V to the new regulator's "IGN"
terminal.

Run a NEW wire from the new regulator's "FLD" terminal to one (either) of
the alternator's field studs.

Run a NEW wire from the alternator's other field stud to ground.

DS

 

Sorry if this posts twice
I'm all clear except on the ignition-switched 12 V. I assumed that
meant +12 V when ignition is on, zero V when it is off. I checked the
chassis electrical schematic and noted that one of the 4 wires to the
alternator met this criteria, checked it with a voltmeter, and used
that. It does happen that this wire is one of the former field
connections. From the schematic, there are several other places to get
at 12 V from the ignition switch (starter solonoid, blower motor, relay
inputs), but they aren't nearly as accessible. Should I be using one
fo these or am I making this way to difficult?
-F

 

You need that wire not to be connected to anything else, so that you can
put a resistor between it and the other original field wire.

Don't believe there's an ignition-on feed at the starter solenoid, but
that doesn't matter, because the starter solenoid is way out of your way.
If I were doing this on a '93 like yours, I'd probably actually trigger a
new relay off of the ASD relay's output (tap into the wire coming off the
ASD relay's 87 terminal, run a new wire from there to the new relay's 86
terminal, ground the new relay's 85 terminal, run another new (fused) wire
to the 30 of the new relay from any source of +12v (alternator B+ terminal
would work), and connect the new relay's 87 terminal to the new
regulator's "IGN" terminal. This way I'd avoid throwing too much extra
load on any of the live-with-ignition-on circuits.

 

I'll let y'all know how it goes.

Thanks,
-F

 

Hooked it up as above, and the charge meter is still sitting at about
10 V. Poked around with a voltmeter, and #87 off the ASD relay does
connect to one of the field post connectors, so right now I'm hooked up
as before, but with a relay and a fused link added.
Should I even be using the charging meter as an indicator of success?
What's the best way to check the new regulator (maybe the new one isn't
working)? I haven't added the resistor yet (my understanding is that
the resistor's sole function is to prevent the check engine light from
coming on - am I mistaken?)
-F

 

What does your handheld voltmeter say across the battery?

Caramba, we've been through this before. It's possible, y'know, that the
wire you keep on using, even though I keep saying not to, is faulty!

Look at voltage across the battery with the engine off and with the engine
running

Correct.

 

What does your handheld voltmeter say across the battery?
Ignition off: 11.5 V
Ignition On: 10.9 V

My mistake, I should have worded that a little differently. I meant
electrically it's the same. I am using the lead coming out of the ASD
relay.

the voltage going in [IGN to ground] and leaving [FLD to ground] the
new voltage regulator is 10.7-10.8 V (makes sense to me, since the
battery with ignition on is only 10.9), so it seems like it's working
as best it can. Is there anything I can check on the alternator? I
measured the resistance between the two field studs (suggested by Nomen
Nescio above): infinite resistance (checked with FLD wire from voltage
regulator disconnected and engine off).

F

 

There you go. Junk alternator.

 

He already replaced the alternator. Are you saying the replacement is
junk, and only lasted a few miles?

I'm wondering what it means that he measures 11.5 volts across his
battery with no current drain. His battery is charged enough to crank
his engine. I always thought it should read a full 12 volts when it's
charged that much.

What symptoms has he had besides diagnostics and meter readings? Is
it possible that some of the diagnostics and/or meter readings are
wrong?

 

Certainly possible, if he bought a parts store "remanufactured"
alternator. Or, he may not have measured correctly. Or, his meter may not
have been in the correct mode.

Yep!