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Well, I'd got it running (thanks Art & volvofromheck for pointing me at the pick-up coil), with some side-tracks... now I've a new problem.
I've a ~20 minute commute along the interstate to work, with a short interval of street driving on each end.
During the day, it's fine, but when I come home at night, with the headlights on... when I get off the off-ramp, all my dash warning lights start randomly flashing when I hit the brakes, and then randomly along the way. (alternator brighter than the others). Sometimes bumps, sometimes slowing down, but it's fine again in the morning. The engine stumbled and nearly stalled when I hit stop-and go traffic at 3 AM yesterday, (more abrupt than my usual semi-coast from 65, and the engine was hunting pretty badly according to the tach) or so it felt like, but then it seemed to be okay when I made it the last mile to my usual off-ramp. (Something about extended high RPMs with the lights on?) Voltage is ~13.5 with every possible load, ~14.4 at idle with nothing on, at start and end of journey. Other symptom is that if I crank the heater blower full on, the alternator light will flare. (Not to full brightness, but it flares, then goes out again.) I'm not sure if I see a faint ghost of the alternator light when I use my turn signals, and the headlights pulse in a way barely noticeable when aimed at the garage wall after I get home. I've one of Dave Barton's adjustable external voltage regulators on there, about 3 years old, Bosch 70 amp alternator put in at the same time.
I've checked the alternator case to negative battery post differential, .1-.2 V, alternator post to positive battery post differential, ~.7 V. The positive battery cable looks a little toasted and mangled (especially that smaller wire going to the headlights, and that wire was hot under the electrical tape, so I decided to replace it anyhow), I've a new aftermarket one on order to replace it. While I wait, is there anything else I should be looking at? All wires going to/from the alternator look tight and secure, but I haven't taken the belly pan off yet (a slow P/S leak makes that a messy job) to check where they run under the engine.
(I'm not even going to mention the level of confused fury I felt when I found out the engine replacement done about five years ago explains why my CIS system is apparently crazy... I don't have a hole in the block for the CIS system's coolant temp sensor with a ~77 engine in there now. Uhm, any options on bypassing that? It also jumps up to 3000 rpm's whenever I plug the IAC in, but I have gone over the vacuum system four times.)
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I had this problem and it was one of the small wires on the back of the alternator. Can't remember what color. but there is only a couple of wires. Make sure they have a tight connection and that the insulation isn't disintegrating. One of the wires sole purpose is to light the dash indicators when the engine is not running.
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"One of the wires sole purpose is to light the dash indicators when the engine is not running."
You actually have it backwards...or sideways. The small red wire's job is to provide exciter voltage to the alternator and a charge warning light to the dash...It just so happens that almost all the other dash warning lights are powered by that same 12V signal.
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I don't see it. You made me get out the green manual. Looking at the wiring diagrams terminal 61 from the alternator goes to a set of diodes on the instrument cluster. This provides a ground through the diodes to some of the indicator lights when the alternator is not turning, the ones that don't have a ground through their sensors at that time. When the engine is running terminal 61 rises to the alternator output, call it B+. so there is no ground through the diodes anymore. The diodes prevent the lights sensor from grounding that B+ voltage.
The battery light does not have a diode, so are you saying a voltage after passing through the lamp excites the alternator? If I unplug that wire the will the alternator not work? Does it just need a very small voltage? It has to be very close to ground to light the indicator lamps.
Anyway the wire needs to be checked.
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The real purpose for the D+ wire in the Bosch system is a secret from most folks until they read Bosch's explanation of "pre-excitation."
Let me see if I can summarize:
Using the drawing I posted earlier in the thread and again below you will see the battery connected to the D+ wire through a 100mA bulb with key in the run position, KP-II.
That is just enough current to cause the rotor to have a magnetic field sufficient to get the stator windings producing alternating current as the rotor turns through them. This current is rectified by two diode arrays. The large one provides the power to the car and recharges the battery (B+), while the smaller 3-diode array supplies the rotor with its full D+ voltage, which is the same value produced at the B+ terminal.
Because now the D+ and the B+ terminal (which the battery warning bulb is effectively across) are at the same potential, the warning lamp is dark.
With no turning of the rotor, no voltage is produced, so the warning lamp is on, finding a "ground" through the rotor and regulator. This "ground" is used as you noted, to provide a lamp test of those warning lamps (BFWS, brake failure, parking) which otherwise could never be tested except by their functions being activated.
If you check the wiring of various years, you will find other systems using this wire as an indication of whether the car is actually running or not, used for the AC, the SRS, and the ABS accessories. It's original "sole purpose" was to get the alternator started, which Bosch calls pre-excitation. As the cars evolved, the wire has acquired a number of purposes.
--
Art Benstein near Baltimore
"Why don't sheep shrink when it rains? Lanolin. This oil causes sheep to shed water. This water-tolerance explains why sheep do well as hydraulic rams." -Spook
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That spanes it. We got way to deep for this topic but good.
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I forgot to respond to your very good question: "If I unplug that wire the will the alternator not work?"
It might, and then again it might not. If the rotor's core has enough residual magnetism (mine are old and they do) you can watch the voltmeter jump up once you rev the engine to about 3000 rpm. It will stay there and continue to function normally until the ignition key is switched off. But, I would not depend on it happening for every alternator.
But you can depend on this: If you unplug the wire after the car is running, the alternator should always work, until the key is again switched off. When you go to see for yourself, do this with a cold engine, because for sure you will knock your knuckles on the exhaust manifold pulling that D+ wire from the spade terminal. :)
--
Art Benstein near Baltimore
I used to be indecisive. Now, I'm not so sure...
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Okay, replacing the positive battery lead got rid of the alternator light when I turn the heater blower on. I have a constant + 12 volts at the exciter wire, but the alternator light doesn't turn on when the car is warm. That is to say in key position two with the engine off I get no warning lights if the car is warm but they turn on just fine when the car has been sitting for a while and cooled off. The battery is a good 12.5 to 12.6 volts when I check it before I start. How precisely does that light test ground, and should I just use FCPs guarantee for a replacement? It's only 22 months old and less than 8000 miles, thus my confusion about worn brushes already.
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Next time lamp test fails (warning lights need to light in KP-II engine not running) even when it is warm, pull the small red wire connector off of the spade lug at the alternator and ground* it. Do the lights now work? Problem is in the alternator or its ground wire. Wear some leather gloves so you don't burn your knuckles on the manifold.
*Don't ground it to the alt case. Get a long jumper wire and ground it at a known good ground, such as the braided wire between firewall and cam cover.
--
Art Benstein near Baltimore
What engineers say and what they mean by it:
"The design will be finalized in the next reporting period"
We haven't started this job yet, but we've got to say something.
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Grounding it at the firewall makes the light test work, more brightly than when it works (cold) plugged into the alternator. I'll try cleaning the stud on the back one more time and redoing the ground strap again before declaring an alternator problem?
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Yes, yes, I think you've got it. You might use your jumper wire to supply a ground to the alternator case to test whether that action changes the lamp situation when it is acting up, because I know many have missed problems with that ground wire hidden from view inside the terminal crimp. But yes, I think Onkel Udo would recommend you just replace that ground wire and go from there. Easier said than done, of course, like everything else needing strange new parts* and a lot of bending over. :)
*I think you might find a stock braided ground jumper in an auto parts store with ring lugs appropriate and not so long you'd need to insulate it. This is not from experience, but from seeing pictures of same on this forum.
--
Art Benstein near Baltimore
What engineers say and what they mean by it:
"A number of different approaches are being tried"
We don't know where we're going, but we're moving.
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"But yes, I think Onkel Udo would recommend you just replace that ground wire and go from there."
I consider it preventative maintenance at this point. Two failures (interment) in two different cars out of six I have owned and one other I have worked on. It does hide well...very well.
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Well, the alternator's dead. Fixing up the wire and cleaning the contacts... made the warning lamp test look a lot brighter... and then they wouldn't turn off. Nothing would make the thing charge. Drove it to my local shop. Shop then lectured at me for daring to work on my own car and told me they never wanted to see the car again after I balked at their quote of about a thousand dollars!!! to replace it.
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Wow!
Do those mechanics think they are Rock stars or something? Forget their concert hall prices.
Maybe their Rocket scientists going to buy a clean room with your money to work on some showroom cars.
Does their waiting room have a cot or plush sofa to put pilgrims to sleep on?
Nobody in your town needs a shop like that but unfortunately they exist!
Its just an alternator. Wonder what they do to hybrid electric car customers!
Scary?
Phil
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Ha ha ha Phil!
I avoid them electric cars like the plague! Not for their alternators which may be expensive to replace, but for their expensive battery, fragile transmission and light body! They can't have tough heavy body like Volvo for energy saving purposes! And talk about crash safety??
To OP:
I've just reading thru this thread but couldn't help but notice like Phil said, its just an alternator!
An alternator consists of its two body halves, two bearings, snubber capacitor, diode assembly, voltage regulator assembly, coil windings at armature and stator. They are NOT complicated. There are many videos at youtube showing how to replace/service these. For me its DIY. During this writing I'm waiting for the shipment of new SKF bearings for my old alternator.
And I'm a medical doctor nothing of engineering background. But hey...I can still read them technical papers! Anyhow knowing technical knowledge may help in troubleshooting BUT we're still stuck with same designs. We still order same new parts to replace same old parts. Technical knowledge may help but you can't change the design (this needs someone with PhD in engineering). So back to simpler life!
Your symptoms of dash light not turning off looks like there is no voltage output from the D+ post. This may be due to defective diodes in the diode assembly (other than faulty ground wires - hope you've checked those). These D+ diodes are usually smaller in size than the main diodes thus they may be easily damaged in use. Replacing the entire diode assembly would do. Cost? Should be around $30 to $60 depends on alternator amperage/part quality.
Here's one website:
http://store.alternatorparts.com/bosch-3.aspx
Regards,
Amir.
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Nah. Brushes or at most slip rings and brushes.
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Grounding it at the firewall makes the light test work, more brightly than when it works (cold) plugged into the alternator. I'll try cleaning the stud on the back one more time and redoing the ground strap again before declaring an alternator problem?
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I think I would investigate your reading of..."the alternator positive post to positive battery post differential, ~.7 V." I see the sine wave symbol. What is that all about? You have to use the DC setting of voltage.
That .7V is way to high. You want it to be just like the negative cable. Even .2 is on the high side. Under .1 is better on big cables!
A tiny Voltage difference means a exponentially high resistance.
The big positive cable is in two pieces on the way to the alternator by the way of the starter motor.
So that's three corrosion or loose points.
I also like Art's bad brushes or worn slip ring idea for low slow speed output. The exciter current is fed through the positive side fuse of the cars cluster he talks about.
You could say we are both on the positive side of this issue! (:-)
Phil
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Okay, off work now.
I was using '~' as an 'about', not an electrical symbol.
Tested at work, ~30 secs after starting: Voltage differential between alternator post and battery positive post, 0.48 V, between starter post and battery post, 0.42 V.
*Ding*
Tested playing with the shifter to keep RPMs up - alternator light flickered a little when RPMs dropped low, but no stumbling from the engine or flaring of the other lights. Cranking heater full on, (high and low RPMs) dim flare of alternator light then out again. Turn signals, no alternator light ghost at any speed. Either spinning Fuse 13 worked, or keeping the RPMs up did.
And now for the pay-off, tested at home, 20 minutes of 65 mph hwy driving with lights on later; Alternator post to battery positive: 0.68 V. Starter post to battery post, 0.59 V.
I think I have a prime suspect. The draw of the headlights is helping heat up the big wire and causing what-ever fault is present to magnify to a noticeable degree, and when the alternator drops output with RPMs, it can't push enough power through that resistance until the wire cools again. We'll see if the new cable does anything.
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Roll fuse 13.
--
Art Benstein near Baltimore
Do plumbers who become electricians install outlets upside-down? Hot on the left?
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Pulled fuse 13, (looked shiny and un-touched) cleaned off the dielectric grease from ~6 months ago, sanded the contacts, put a new ceramic fuse in, re-greased. (The effort on cleaning and greasing those months ago has left that the nicest that fuse box has ever looked since we got the car in 2010 or so... that was the best investment of a half hour I'd made on eliminating electrical gremlins since I learned about the fuel pump relay.) How would fuse 13 cause the electrical problem, by the way? (Or was that for the ongoing CIS saga?)
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Having Constant Idle System without the temp sensor is another topic. If you can't get the sensor into that head, you certainly won't benefit from connecting the IAC. The 77 used an air slide for that purpose up on the cam cover, so maybe you could match that control to the engine. Maybe you still have it. Anyhow that is good for another thread, I think.
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Art Benstein near Baltimore
Why is the man who invests all your money called a broker? Especially today?
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"How would fuse 13 cause the electrical problem, by the way?"
Obviously "roll fuse 13" is a hip shot. It has been a remarkably successful one over the years-- so much so I was thinking of adding a humor-intending copyright symbol.
The symptom where the battery light pulses with other loads to fuse 13 indicates a voltage drop between the battery and the load side of the fuse panel, where the turn signals and the instrument cluster (warning lamps) share wiring. The most likely place for that high resistance (for those who haven't done the fuse panel diligence) is in the contacts of fuse 13. But not the only possible place. I think I'd be looking at the slip rings and brushes.
Getting you to roll fuse 13 isn't much of a wasted effort if not the answer and it is certainly an easier thing to explain than the use of a multimeter to locate the voltage drop causing the warning light to come on. You might find this drawing helpful, but it does not account for the accessory variable external voltage regulator you have. The 81 wiring supplies the cluster warning lamps, turn signals, seat belt warning, fuel injection relay, and constant idle system through fuse 13.
--
Art Benstein near Baltimore
All the trouble I've ever been in started out as fun.....
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From your first paragraph I'd be for checking your battery leads but I see you're on to that. The positive lead can corrode under the insulation to the point where it may show volts OK but doesn't like to carry current (amps). Earth can be the same but the fault should be more visible. Often mentioned is the possibility of damage to the positive lead where it goes under the front of the engine but you'll see evidence, if any, of that when you do the replacement.
Do the early cars have the small earth lead from the back of the head to the bulkhead? That's useful backup. Clean back any earth connections at the body end.
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Ground strap from the head to firewall is freshly cleaned and reattached. Iirc, the new positive cable has a clamp, lead to the starter, and the smaller wire to the headlights. If I had to replace the under engine big wire from starter to alternator, where would I find one?
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