HELP! Electrical challenge with Alternator

[sjx40250]

Didn't think I would have to use HELP in any of my titles!
Info:
90 Laredo AW4, 242, Tow package ETC.

Had a problem with a screaming bearing in my alternator. it was a CS130. Found the bearings and replaced them. Used a CS 120 during the interm. Found the following problems during this time.
The ammeter would intermitantly charge and behave as normal and then not charge at all.
In fact, over time, the battery got drained very slowly, like a week. At the end of the week I drove it (it is my wifes DD) I noticed that the needle was nearly in the red. I was somewhat alarmed and used the charger to bring it back up. The problem persisted.

During this time, I had challenges identifying the bearings needed for the CS 130. I found them installed and swapped alternators.

Initially it looked great. After 15 years, I was finally able to educate my wife to look at the gauges! She reported that the problem was back. Well I have been busy, but while I was out of town she called and said not only was the needle in the red but the Oil Pressure gauge was pegging above 80 PSI! She didn't want to drive it that way. The education paid off.

I checked it tonight and found that the ammeter is below the red and the preassure gauge does go above 80 and then fluctuates down around 80 acting very intermitantly.

Any ideas where I can start? I suppose I should pull the alternator and have it tested but why would the oil pressure gauge be acting up? I think they are related.

[8Mud]

The high oil pressure is usually an open circuit, if you unplug the oil sender, the needle will go all the way up. An oily connector at the sender, has been known to make them act up, along with a bad sender and occasionally a gauge. Guess it´s possible, for a bad connector (or ground) at the dash to affect both the volt gauge and the oil pressure gauge
Check your charging circuit at the battery with a volt meter, really the only way to know for sure what´s happening. The volt meters in the dash are notoriously inaccurate.
I recently had an alternator act up on me (after a coolant bath), swapped in my spare and it acted up after a couple of weeks also. Number one was a failed diode and number two was a failed regulator. Chit happens. I´m on number three now, that´s been going over a year. I rebuilt number one and two, just in case.
The battery cables and the alternator wires are the first things to check. Make sure the charging wire that runs to the starter relay is tight. The plug into the back of the alternator is clean and the wires aren´t frayed or cooked onto something. The I/F wire at the back of the alternator should be close to battery voltage with the ignition on.
If the alternator is charging low, it´s often a diode. If it´s charging sometimes, it could be the I/F wire going to the back is loose or dirty. Or the regulator overheats and acts up. Most any kind of mud, oil or coolant, on the slip rings and brushes aren´t a good thing and can also cause trouble.
Pin hole radiator leaks, that spray back onto the alternator, are often fatal for the alternator, I´ve seen it on numerous occasions. Don´t exactly know why, but the cause and affect are obvious. First the radiator leaks, then the alternator dies.

[dizzymac]

just replaced my alt. due to a no charge situation, put in new one and all was good 'til the next morning when I noticed volts at about 8v. Let it run a min. and it went up to about 12v. Went to work and came out to same prob., hit the gas and got fanbelt squeal,put alt. under load and got the same. replaced the belt, couldn't get it to proper tension, to old. All is well now with new belt. Good luck

[sjx40250]

Thanks for the response.

I did check all the connections at the starter relay for grounds. The one that did show a ground was the circuit that included the hood light.

The alternator is really clean cause I just had it apart. The connections are also good. I have a tube of OX GUARD that I very carefully use. This is a DD and been owned since the dealer lot. Being in Oregon and not having been off road much with this one, it is really clean under the hood.

Checked for baked wires without finding any. I did finally discover the fusable links. Been looking for years. Guess I can't read and I didn't know they were green!

Thanks for not pointing out how stupid I was to label the volage gauge as an ammeter! I would expect consistant readings even if they aren't accurate. If there was a ground problem at the dash, then I would expect to see problems with the other guages too.

Sorry, I am having diffuculty understanding what the I/F wire is. Is that the one that is labeled BAT at the Alternator? In any case, it is tight and clean (still has the rubber boot).

[Runnin'OnEmpty]

I did check all the connections at the starter relay for grounds. The one that did show a ground was the circuit that included the hood light.SJX, if you have a short circuit in the hood light, that would quickly drain the battery. I'd unplug it, until you determine for sure what's wrong.

One thing to check that hasn't been mentioned, is the battery ground cable where it connects to the engine block. It's a 1/2" nut that will cause all kinds of electrical grief if it isn't tight.

[sjx40250]

I will check the ground. I also checked the cable from the alternator after starting. I did not get increased voltage. I think my alternator has a problem. I found a diagnostic instruction set on line that I am going to go through this week end. And then have it checked at Shucks or Autozone.

Thanks for your responses!

[8Mud]

Thanks for the response.

I did check all the connections at the starter relay for grounds. The one that did show a ground was the circuit that included the hood light.

The alternator is really clean cause I just had it apart. The connections are also good. I have a tube of OX GUARD that I very carefully use. This is a DD and been owned since the dealer lot. Being in Oregon and not having been off road much with this one, it is really clean under the hood.

Checked for baked wires without finding any. I did finally discover the fusable links. Been looking for years. Guess I can't read and I didn't know they were green!

Thanks for not pointing out how stupid I was to label the volage gauge as an ammeter! I would expect consistant readings even if they aren't accurate. If there was a ground problem at the dash, then I would expect to see problems with the other guages too.

Sorry, I am having diffuculty understanding what the I/F wire is. Is that the one that is labeled BAT at the Alternator? In any case, it is tight and clean (still has the rubber boot).

The I/F wire is in, the small plug that plugs into the back of the alternator, I said I/F because I couldn´t remember the color (which I beleive is yellow). The connection is labeled I/F on the case of most alternators. The tan wire coming out of the same plug, is for the alternator idiot light (if present).
For the Dodge people, it´s the ampmeter for most everybody else it´s a volt meter.
Check the yellow (I/F) wire for near battery voltage with the ignition on. If it´s getting near battery voltage and the major wire from the alternator through the fusible link to the starter relay and then to the battery is good (no resistance checked with a ohm meter) and the battery lugs are seriously clean and the grounds also. The problem is most likely in the alternator.
I always look real close at the I/F wire, it was a serious trouble spot in the early Renix, which I thinked they improved or cured in 89. This wire goes through numerous connectors, after the ignition switch and has a history of flacky contact at the connectors.
http://www.alternatorparts.com/cs130_sbpage1.htm

[sjx40250]

8Mud, Thanks for the info! Already found that site. It is a good one. I will check tomorrow. The I/F wire check is great info. Thanks. Spent some time in Central Germany around Frankfurt many years ago.

[sjx40250]

OK so I tested the BAT lead and the fusable link is good. I also turned on the ign and got bat voltage at the I lead but not the L lead. What should I look for now?