Erratically overcharging and undercharging

[cout]

On the way home from the most recent 24 Hours of LeMons at CMP (where my turbo voyager received more compliments than our race car *grin*), we had one of the worst rain storms of the year. The vehicle started acting like it was running on 2 cylinders. Couldn't figure out what the problem was, so we replaced 2 loose spark plug wires.

Next day on the way to work I went through a puddle and blew a fuse (on the circuit that goes to the shutdown relay). When I purchased the car, it had been blowing this fuse, but the problem turned out to be a short in the wire that goes to the fuel pump. That was fixed already, so I figured it must be some other part of the circuit with a more intermittent problem.

That was the start of my problems. Since then:

* the battery went dead and when I replaced it I discovered the alternator was not charging
* replaced the alternator with a higher amp ND
* still can't get a charge - time to pull out the multimeter
* varying potential across battery terminals (11.5 - 13.5V, depending on whether the battery is charged and whether I'm revving the engine)
* 12V at the one field terminal (to ground) and 9-10V from the other to ground. about 1.5-2.5V across the terminals (but not exactly the 1.8 that I've read can happen with a bad voltage sense wire).
* full field produces 18-20V from the alternator
* tried to install an external regulator but no luck getting it to work
* next time I drove the car instead of undercharging it was producing 13.5-14V - YAY! But then when I got on the interstate it started climbing up, a little bit at a time, to 18+V, until I turned on the headlights to bring it down to 16V
* next time I cranked the car up it was undercharging again.
* checked the voltage sense wire. the connection to my splice was loose, so I redid the splice. cranked the car up and it was overcharging again, but it didn't last long before it was undercharging again on a subsequent crank. btw the voltage sense wire is labeled incorrectly in the 1989 service manual (both the color and the name) -- took me a while to figure this out.
* time to redo all the wires from the beginning. removed all the friction tape and retaped all wires that hadn't been messed with. all the other wires (which have been re-spliced) will be taped separately. replaced all the fusible links with links from a junkyard v6 (not exactly the right gauge but it will do for now).
* removed the computer to check the power module. nothing obvious until I cleaned off all the grime:



Could this be my problem? (looking at the brown capacitor whose rubber coat has worn off)

Questions:
* If this is the problem, maybe I still have a chance of getting the external regulator to work?
* If this isn't the problem, what does this capacitor do? Do I need to replace my power module? if I need to replace the power module, where do I get one?
* What is the extra connector (one red and one black wire) on the v6 power module (connects to the LM)?
* Why are the wires from the battery to the fusible links and from the fusible links to the starter relay red on the '89 V6 and black on the turbo? AFAICT from the service manual both should be black on both cars.
* What is the proper way to ground an external voltage regulator? One of the regulators I purchased was painted and the paint doesn't conduct electricity. There is an exposed metal connector on the front but I'm not sure how to connect a ground wire to it.

[A.J.]

It sounds like you have a bad wire going to your alternator. I forget exactly how it works, but one of the terminals on the back of the alternator goes to the computer/voltage regulator. The computer grounds or sends power to the terminal on the alternator and the alternator output goes up or down. I had an alternator not charging. But bench testing it, it tested okay. Instead of cutting open the black box that the wires go through on the back of the alternator, I just bent the terminal away from the post and ran a new wire to the computer. That fixed it. It sounds like you have an open or a short in that wire. I'm pretty sure it's the post closest to the ground. I'd check my van for verification, but it's at work. You need a wiring schematic and check to see if you have zero ohms in that wire and no shorts to ground.

A.J.

[turbovanman²]

External regs are easy. As for the ground, just bolt the external reg to something metal after removing the paint-assuming you bought an early Dodge reg.

Sounds like a wiring issue for the field wires, so triple check, if ok, replace the SMEC.

Wiring diagram for the reg-

http://www.turbo-mopar.com/forums/sh...95&postcount=4

[cout]

I *think* I've fixed the problem. I've thought that before, though, so time will tell.

What I did:

* cleaned off the PM and applied silicone weather sealant around the edges and over the exposed, broken capacitor (still curious exactly what that capacitor does). Also applied sealant to the LM where the original seal had broken off. Was careful NOT to get any sealant on the heat sinks.

* fixed almost all wires that were taped or spliced and replaced the questionable connections with proper soldered connections and heat shrink tubing. In particular the injector wires were in bad shape; some of the positive wires were exposed and shorting out. Had to remove the fuel rail to do this, so I went ahead and cleaned out all the grime that had accumulated underneath it while I had the chance. Made extra sure that the junction of green/black wires had a good connection, since this is the junction where the voltage sense wire connects.

* cleaned up sloppy runs of wires so that they now run parallel to the original wiring harness

* grabbed fusible links from an '89 V6 voyager and soldered them into place (at the time of my previous post I had only crimped them and the wires going to the ignition switch were too long so it was rather sloppy). I would rather use a fuse box but none of the cars in the junkyard had a fuse box that suited my needs.

* side effect of replacing fusible links is that the alternator is no longer connected directly to the battery (Custom Automotive Electrickery - http://books.google.com/books?id=jL2bmss8LXsC - "The Remote Voltage Sensing feature is a big advantage when running a non-factory, custom-built wiring system.... This system only works properly when a properly rated wire connects the battery to the junction (see Figure 26 Correctly Wired Alternator). You should never connect the alternator directly to the battery. In the example illustrated in Figure 27 Incorrectly Wired Alternator, the installation of the alternator includes a heavy gauge wire from the alternator directly to the battery. The voltage sensing wire is routed to the junction, and the voltage regulator will maintain the junction at the correct 14V level. However, as the voltage regulator compensates for the voltage drop, the alternator output could be over 16 volts, overcharging the battery via the extra charging cable."

* replaced all the rotting friction tape with fresh tape (tried both the cloth friction tape and the cold shrink tape, and while the cold shrink tape definitely looks nicer, the cloth tape is much easier to work with).

* fixed wiring of black/red disconnect next to SMEC/battery (can't remember how it was run but it wasn't right)

* replaced failing ground strap (the one that connects the IM to the body) with four 12-gauge wires (crimped them to the original terminals with a copper splice, filled the splice with solder using a butane lighter, and covered them with heat shrink tubing). The new ground strap actually looks pretty good, except that the only tubing I had that was large enough was clear plastic, so it shows off my crappy soldering job.

* moved ground wire that was connected directly to the cylinder head to connect to the transmission instead (yellow wire that was running alongside two other wires that are connected to a sensor of some sort on the transmission). I figured this made more sense than the way it was run.

* cleaned off every electrical connection I could reach, first with a dry cloth, then a wet cloth, then with alcohol (I tried isopropyl and ethyl -- I think the isopropyl works better but I'm not sure). Cleaned the wires with alcohol as well, so they look pretty.

* no external regulator in the system other than the PM itself

Voltage meter in the car now reads a little high (sometimes it's straight up and down, sometimes it's a little bit to the right), but voltage at the battery is right at 14.3-14.4, regardless of whether the headlights and accessories are on. Woohoo!

Now the idle is creeping up occasionally (suspecting PCV) and the cold weather is making the alternator belt squeal like an ADHD parakeet. I'm not complaining, though; at least it's drivable!

[tsiconquest88]

Overcharging would have been just a bad reg in the alt, a good used or new alt would have solved it rather than an external reg. The stock alt reg is still bad then anyway. Probably also why the belt is squeeling, the alt is probably messed up too. Also Are you sure the AC belt isnt the squeeling culprit? I had numerous problems with that darn thing and finally got it right before i had the darn electrical isse. But maybe it loosened up? Just a suggestion. Either way i would ditch that old --- alternator anyway at this point since it already overcharged.

[mark]

he mentioned he changed the alt.

* fixed wiring of black/red disconnect next to SMEC/battery (can't remember how it was run but it wasn't right)
* no external regulator in the system other than the PM itself

you have a smec and a PM? i thought PM/LM was replaced by SMEC/SBEC?
for squeel ->does the alt belt line up perfectly withthe pulley? how are the alt bushings
when i had charging problems on an old omni i had it was the PM that I had to replace, that was before i knew about switching to an ext reg

[cout]

you have a smec and a PM? i thought PM/LM was replaced by SMEC/SBEC?

A SMEC is a PM+LM in a single case (the intent being to reduce the bulk of the wiring harness):





In the second pic you can see the PM on top and the LM on the bottom (which would normally be underneath/behind the PM).

for squeel ->does the alt belt line up perfectly withthe pulley? how are the alt bushings

The belt seems to line up fine, but I need to try the water trick mentioned in the service bulletin:

http://www.turbododge.com/forums/f4/...or-squeal.html

"Set the parking brake, shift the transmission into neutral and start engine. If the noise is being generated near the front of the engine, a spray-type water bottle should be used to spray the grooved side of the alternator belt with water while the engine is running. If the noise subsides and then returns as the belt dries, perform the repair procedure. If the noise does not subside, alternator misalignment is not the cause of the noise.

(I had a link to the service bulletin pdf but I can't find it right now)

The bushings were questionable. Where can I get new bushings?

when i had charging problems on an old omni i had it was the PM that I had to replace, that was before i knew about switching to an ext reg

I couldn't get the external regulator to work after multiple tries. If my PM ever gives me trouble again I might give it another shot, but given that the PM controls more than just charging, I'm not sure if that's what I'd want to do.

[cout]

Overcharging would have been just a bad reg in the alt, a good used or new alt would have solved it rather than an external reg. The stock alt reg is still bad then anyway. Probably also why the belt is squeeling, the alt is probably messed up too.

On our cars, the regulator is in the power module, not the alternator. The rectifier is in the alternator. I keep getting those confused, esp since in newer cars the alternator is internally regulated. Anyway, as I mentioned replacing the alternator was the first thing I tried. I thought that solved the problem but it came back later. I think I've now finally fixed the problem once and for all, though. I had screwed up the wiring when I originally put it all back together. One problem was a loose connector on the voltage sense wire. That was definitely a problem but it couldn't have been the only problem, because I was still having problems after I fixed it.

I also had the alternator connected directly to the battery positive instead of going to the junction. Apparently this can be problematic because the voltage regulator senses less voltage than is actually being produced (due to resistance in the wire). If no voltage or too little voltage is detected, the computer can put the car into a mode where the alternator is only producing a trickle, in order to prevent overcharging.

Once I properly soldered all the junctions and put the wiring back to mostly stock, with the alternator connected to the junction via a fusible link, my charging problems went away.

Also Are you sure the AC belt isnt the squeeling culprit? I had numerous problems with that darn thing and finally got it right before i had the darn electrical isse. But maybe it loosened up? Just a suggestion.

That could definitely be the culprit. I had assumed it was the alternator belt, though, because I didn't have any belt squeal until I replaced the alternator. But I could easily have bumped something or messed up the tension on the A/C as well.

[tsiconquest88]

Mark- The bushings are new from johnny. He said pm, but he means smec thats all. Its just a socketed smec like any of the turbo mopars within the sme years has.

[ShelGame]

* What is the extra connector (one red and one black wire) on the v6 power module (connects to the LM)?

That's the control lines for the 3rd injector bank that the V6 uses. Not sure why they ran the wires like that - both of those lines go out on the 60-way also. They could have simply made a 'new' power module with a 16-way connector instead, but they didn't.