Mrmerlin

Tim the damaged insulation will become apparent when you remove the back side of the 14 pin connector covers, take a picture after the covers are removed , I have see way too many connections here even on newer cars where the insulation is falling off and wires are bare

Alan

Humm - I guess you don't believe me...

Mrmerlin

Alan, I mean you no disrespect, In fact I alwas would defer to you for elex problems, but since the car is so old the 14 pin connectors seem to shedd insulation and I am only posting this because the OP may not have investigated this possibility.
I know that you have waaay more elex wisdom with these cars than most people including me but there are alternator wires that pass through the 14 pin connection and if any of them are touching or broken then this could be a possible source of the problem.
I see the OP is already going for another alternator but my guess is a faulty wire connection

j.kenzie@sbcglobal.net

Hi Alan,
My comment about voltage spike was off the mark. I meant sustained overvoltage events due to the alternator not thinking it is connected to a standard voltage battery for reference voltage. Looking at the wiring diagrams, there is no wire going directly from battery to alternator, but they are each connected to the starter. This give some connections and cables to check. Also you raised the possibility of internal battery damage which again shifts the reference voltage.
Just trying to help.

Alan

Guys - not trying to be argumentative here - but its so easy for this stuff to go of track... and in confusing circles.

The important thing is to be methodical and go through tests that narrow down the possible options.

The battery indeed connects via the starter to the alternator. Overvoltage could only be caused by battery disconnection so these are the places to look.

The jump post isn't in this circuit - it does connect the alternator to the Central Electric panel - it could be the cause of dashboard voltage irregularities or other effects (relay problems etc) but Tim doesn't have these since the voltage measured directly across the battery terminals ~matches what he sees on the dashboard.

This pretty conclusively means the battery is connected (at least at the terminals) and that the jump post connections are good. Cleaning them of course certainly does no harm. There may also be restoration work that may be needed to prevent future issues - but it seems it is not the issue this time.

It may be worth looking at the alternator exciter circuit (61) at that connector - only because it may also be a seperate problem related to the occasional no-generation issue (that cause is possibly different to the overvoltage condition).

Alan

Alan

Dave - I understand your thinking but thats not the way it works. The battery doesn't serve as a reference voltage for the alternator - its best to think of it more like a giant smoothing capacitor - as in an AC to DC rectified power supply. During the gaps between the phase peak voltage generation the battery supplies current to keep the ripple voltage relatively low.

Think about it...

The battery is connected directly to the alternator by a big cable - once the alternator starts generating at 14.2v - that is the voltage on the battery terminals too... and it is charging at a rate dependant only on its internal resistance - there is no longer any reference voltage available other than what the alternator puts out.

Thats why I say its a self contained system. The only external input is the 'start generating signal' (exciter circuit).

Many think the alternator has smarts it just doesn't have. It has no idea if the battery is charged or not... its job is just to generate 14.2v at all current loads... it tries to do this as well as it can given the energy input avalable. It should never generate more voltage (rms) but will sometimes generate less voltage if it cannot sustain the total power requirements (e.g high curent at idle). The alternator regulator alone controls this voltage level - the battery helps it regulate better particularly to reduce noise. If the battery disconnects there will be a temporary large voltage spike due to major load reduction as well as increased voltage ripple and poorer voltage regulation.

Alan

85fortheDrive

I removed every bullet pin, cleaned it, and inspected the wiring. There is some minor corrosion, but all the pins (both male and female) and wires LOOK okay.

My attending to Merlin's suggestion is in deference to the multiplicitous nature of electrical problems. I do understand that the 14-pin connector is not in line with the battery-to-alternator circuit. But I figure it can't hurt to thoroughly clean it.

I'm learning from great tutors here, with Alan being the emeritus.
Meanwhile, Rog is sending another alternator. I drove the car to work today (25 miles in dry weather) and it performed like a champ. DMM is still hooked to the battery posts so as to continue to gather evidence.

Thanks to everyone...

j.kenzie@sbcglobal.net

Thanks Alan,
I was just trying to figure a way for a new and twice tested alternator to give 16 volts. I am out of ideas and hope you guys figure it out. I am glad you're there to help.

85fortheDrive

Meanwhile, more data from today. On the drive home, again with the DMM connected to the battery posts, the voltage dropped off from the alternator. For about 12 minutes of the drive, there seemed to be no voltage output from the alternator - DMM read 12.2 volts during that time. With a mile left on the drive, the alternator kicked back in and I got 14.3V.

Probably the last commute with the OB until I get the new alternator in. But it sure was nice driving him in the sun today

Tim

ROG100

Alternator will be with you on Friday

Landseer

Tim,

Exactly to which coordinates of the CE panel is the DMM now attached? I may want to duplicate.

Did you take a picture of the back of your insturment cluster when you had it out? / if so, please show.

My system with varies downward in voltage read somewhat. But I've not seen it cross the 14 V threshold.

What else, electrically, is not yet sorted-out on your car?

85fortheDrive

Have I mentioned that you're the best?

At present, I've actually connected the DMM to the battery posts. Prior to that, though, I stuck a lead into one of the main red feed lines (between the N and O wire junctions at the bottom of the CE panel) and then clipped another to one of the the CE panel ground points, which is above the panel, somewhat obstructed by the back of the passenger storage "tray".

Have you ever taken your instrument cluster out? I don't have a picture of mine, but will be happy to take one for you next time it's out. I'm intrigued by the overlapping experiences we're having. We have the same car, basically.

If you need help with pod removal, just ask; I've had mine out at least eight times.

I have yet to examine the backside of the CE panel, but other than that, I think I've covered most of the electricals. There is a ground point in the back hatch that is behind the passenger side paneling - I haven't accessed that yet either. Just about everything else has been examined and/or replaced.

PM me if you want more info - I'm grateful for the collaboration.

Peace,
Tim

6mil928

If Alan says it then it's the electric gospel. Alan has never steered me wrong. Jason

Alan

He most certainly is !!

Your new symptoms of stopping generation after the car has started up and initially generated OK are unusual (but so is all of it...)

If this continues to happen I'd suggest you monitor the (61) exciter circuit and see what its doing. For the alternator to stop generating after it has started up suggests either an internal connection issue in the regulator or that the exciter circuit is shorting to ground. If that happened I'd expect it would fry the alternator pretty quickly - the phase diodes for the rotor are not designed for high current... Its probably more likely its also related to the other voltage issue...

However you can check (61) on the CE panel pin O8 or H8 or Y6... OR its also available on Pin1 on the 14 pin connector in the engine bay.

Alan

Alan

85fortheDrive

Okay, another interesting idea here. I am intrigued by the notion of this circuit deteriorating the alternator. This is, after all, a new (remanufactured) Bosch alternator.

What are you referring to with the "(61)"? From your direction above, if I insert a DMM probe into H8 and the other to ground, then will I be able to study the exciter circuit? Just to confirm, the slots in the CE panel plugs are numbered as:

4 8
3 7
2 6
1 5

Correct?

More homework!

And Alan, don't forget that you're on the list...