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The interior lights and headlights have been dimming and brightening when the engine is running. The alternator light does not come on. When I hit the gas to get more RPMs the flickering speeds up but does not go away. Any ideas? When I am driving at night other drivers think that i am trying to send morse code.
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Flickering lights on a brick is the classic symptom for worn brushes. My diagnostic procedure for this symptom would have been to remove the voltage regulator from the back of the alternator and look at the brushes.
The fact that the flashing has stopped and it is no longer charging at all tells me that most likely the brushes are no longer contacting at all.
You can find new brushes for this alternator for $5-10 and solder them in place in about 10 minutes, or you can buy a new voltage regulator for about $60 and replace it in the time it takes to put those two screws back in. I soldered in new brushes at 150k miles, and then my voltage regulator failed at 250k miles, so I have done both procedures.
It is much easier to access the voltage regulator screws if the oil filter is off.
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it sounds like your voltage regulator is no longer maintaining charging voltage to spec. if the voltage regulator is allowing the battery charging voltage to EXCEED 14.5 volts give or take your lights will on balance getter brighter than normal.
if the multimeter reveals when placed across the battery terminals with engine running your voltage exceeds 14.5 check out the regulator. you will boil off your battery acid fast with charging voltage to high.
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I should add that the engine surges while the lights are dimming and brightening.
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Lots of possibilities as by your statement, it does not sound like any troubleshooting has been done yet. My gut reaction if the the brushes in the alternator are wore out, but lets do this methodically:
Check Voltage at the battery posts (not the clamps) with the car off, should be about 12V give or take
Check Voltage at the battery posts with the car running at around 1500 RMP, should be about 14V give or take
If either of these #'s is low you have, most likely, a charging issue or a bad battery...most likely the brushes but could be other culprits
If that checks out the search gets a little harder. By the way, does the alternator idiot light come on in key position II? How old is the battery? How old are the belts.
Onkel Udo
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The alternator light comes on in key position. The battery is three years old. The belts are new.
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I will assume that the alternator light comes on, but does go out after the engine starts. I have had on three occasions with BOSCH (others possible I think) alternators where one of the brushes wore down faster than the other and the alternator stopped charging AND the alternator light DID NOT turn on.
Some links worthy of viewing:
http://www.brickboard.com/RWD/index.htm?id=725699&show_all=1
http://www.davebarton.com/AdjustableVoltage.html
First, REMOVE THE NEGATIVE CABLE FROM THE BATTERY AND STOW IT! Remove the alternator, then remove the voltage regulator assembly (held in with 2 screws) from the back. If one brush looks shorter than the other, you have three choices if the brush contact surface is not overly grooved (if it is overly grooved, I would go to a rebuilt alternator):
- Buy a replacement voltage regulator. If it's a Bosch alternator I would stick with Bosch voltage regulator ($32-$38)
- Simply replace the brushes with a soldering gun. A new set of brushes cost about $6-7. Your local NAPA may be able to get them to you in a day. Order a couple of sets. I keep one set in my spares box.
- Do both above. Install the new one and keep the repaired one as a spare.
A few important points:
- When you solder in the new brushes, make sure that the distance between the base of the brush and the base of its socket remain the same. This is to protect the commutator from ever making contact with the wire in the base of the brush. Doing so can damage the commutator permanently
- If one brush is markedly shorter than the other, its commutator mate is wearing the brush out faster. So you may be changing that brush out more often.
- As mentioned by another poster, check those connections at the alternator and where they terminate.
- Good time to pull out the Bentley manual and clean up all of the grounds.
Keep us updated and good hunting!
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Since the belts are new, check the tension on the alternator belt(s) first. They do stretch some in the 500 miles or so, but doubt that is it. With the surgin problem, I suspect a ground issue now. Most likely a broken chasis to engine ground strap or even the alternator ground wire has failed.
Either way, check the voltages with a multi meter and get back to us. With the hood open you can easily inspect the ground strap and main battery clamps/cables but the alternator ground wire is trickier because of how it fails (corrosion inside the ring terminal).
Onkel Udo
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Thanks for the idea. I checked the voltage across the battery with the engine off, 12.26 volts, With the engine running, 11.98 volts. Now the surging and lights flickering have stopped, but the alternator idiot light comes. When I gun the engine, it goes off.
I tried to check the engine ground but could not see it. Could you tell me where it is located? Thanks.
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OK, when your voltage goes down with the car running, that means you are absolutely not charging. The Alt light on indicates the same thing.
I have no actual car in front of me (or within a few thousand miles) so I am going by memory but...there are two major grounds for the engine bay area; the battery post to starter and a braided ground strap from the block to the firewall. Either of these could be suspect but since your starter works fine, I would bet on the chasis ground strap...if I did not think it was the alternator ground or feed wire.
You alterator is not producing power as mentioned before. There are only three common faults that cause this outside of the obvious (alternator not turning):
Damamged or disconnected small red wire to the alternator.
Damaged ground wire from the alternator to the engine block
Wore brushes/regulator bad (one piece to replace so I lump them together)
What I would do is remove the alternator from its mount to easily check all three. Disconnect the negative battery cable, loosen the pivot bolt, untension the tensioner and then unbolt the alternator...just let sit there but with the back of the alt facing up (you will probably have to unplug the red wire and ground wire so keep track of where they plug in)...remove the two screws on the regulator/brush plate. Remove the regulator thing and see how far the brushes stick out...if it ain't far, replace it but keep the old one.
Next, inspect the small red wire as far as you can't follow it. Give the end a gentle tug. If all looks well, that is not your problem...probably.
Finally, reach down to were the alt-to-motor ground wire is. These fail because of vibration, corrosion and oils saturation. Give both ends a good tug. In my experience, one will end up pulling free about 20% of the time.
Onkel Udo
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You all have helped me a lot. I did the voltage testing, checked the grounds (motor to chassis, alternator to motor), and both were good. i removed the alternator, tried to remove the voltage regulator, and ended up breaking both screws. In any case, the alternator was loaded with corrosion. i replaced it with a rebuilt and the car charges fine.
The only problem I now have is that the idiot lights, with the exception of the battery light, stay on after I start the car. Did something I did cause that problem? I looked at the Bentley manual for a common source, but could not see one. It is as if those lights are all stuck in test mode.
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After start, give the motor a good rev. Do the lights go out?
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The lights, with exception of the battery light, stay on. I checked the voltage across the battery posts with the car running. 11.86 volts.
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Let's check a couple of things:
1. When you turn the ignition on, but do not start the car, are all lights are on INCLUDING the battery/alt light?
2. If the battery/alt light is NOT on and the others are, then start the car and take the engine above about 2000-2500 rpm. The alternator needs 12v to "excite" the alternator and normally it arrives via the battery through the battery/alt light. When this has happened to me in the past, I could wind the engine rpm up and the alternator would self excite (actually called excitor, but what the heck). If the light goes out, now check the output voltage at the battery and report back.
Regardless, you should trace the +12v circuit to the alternator. The battery/alt bulb is part of that circuit. If it's burned out (rare), then replace it (swap it) with one of the other bulbs like the service light.
If it's not the bulb, I would double check my work at the back of the alternator to make sure I reattached everything (small and large red wires). Next check continuity of the wire from the alternator to the battery and then start checking grounds. I would be surprised if a alternator out of the box was bad, but it happens.
Question for the forum. Is there a dedicated ground wire running out the back of the alternator on a 1992 and 1993? It looks like it gets it from the alternator casing to the mount to the block. I took a look at the wiring diagram and the back of the alternator and there appears to be a small black wire as part of the capacitor, a small gauge red wire with a quick disconnect going to the alternator/battery light and of course the 6 gauge wire to the starter/battery.
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Voltage should be 13.5 to 14 volts, a new Bosch voltage regulator or brushes should fix this.
Dan
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I failed to mention that I just installed a new alternator.
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I would get the alternator checked out then because it does not seem to be working. If the battery light in your dash does not work, check the small red wire to the alternator and the bulb in the cluster.
Dan
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Measure the Resistance of the chassis of the Alternator to the Chassis of the Engine Block.
You should have Zero Ohm's when you do that. If the Alt housing is not grounded the system will not charge.
Another Check already suggested is to turn the Key to POS II and look at the Warning lights. If the Alt, Brake, and Oil lights are not all on before you start the engine, there is a problem with the Ground or the little red wire on the back of the Alt.
Regards,
Paul
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Thanks, I checked the grounds, little or no ohms resistance. All of the lights come on at POS II key position. I don't know what else it could be if it is not the alternator.
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Are both red wires connected to the back of the Alternator?
With the ignition on (engine not running), is there +12v at the smaller red wire connector that connects to the back of the alternator?
After engine start, rev the motor above 2000-2500 rpm. Does the Batt light go out?
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Both red wires are connected and there is 12 volts at the small wire connector with the key on.
The BAT light does not go out when I rev the engine.
Thanks.
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+12v at terminal 61 (D+) is good. At least the excitor circuit is getting 12v. Since it won't self excite with a higher rpm, the alternator/regulator is the suspect.
With the alternator belt installed and tightened, there is one more test.
With the ignition off, check for +12v at Terminal B (threaded connector at the back of the alternator where the larger (6 gauge) red wire ties into) and ground (try using the casing of the alternator as the ground, then the engine block and finally the negative battery post to see if there is any difference...there shouldn't be). If there are what were the various voltage readings? A fully charged battery should show > 12.6v
If you have +12v, then the book sez bench test the alternator/regulator. I recall you stating that you just installed this new/rebuilt one. Was it a Bosch rebuilt or aftermarket?
We're hanging in there with ya.
Don't forget to disconnect the negative cable off the battery if you R&R the alternator. Don't want to do any unplanned arc welding.
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Thanks to all of you for your help. I reviewed what you all have said with a professional mechanic who I ran into. He did some testing and confirmed that the alternator/regulator is bad.
The new alterator that went bad was an aftermarket rebuilt, not a Bosch. I am in the process of getting a Bosch.
Brickboard is a great resource. I am glad to be a part of it.
Tom L.
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