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Sages,
So I've been working on my 1991 to get it back on the road and safe to drive, as it is going to become my daily driver here for the foreseeable future.
I get everything back together yesterday and my wife and I head out to dinner in it to meet up with some friends. No problems to dinner.
On the way back I fire up the car and I get the following lights on my dash board glowing dimly: service, battery, brake, brake failure and bulb failure.
The trip take about 30 minutes to get home, but I have no problem getting home. No dimming headlights, no nothing, just the dimly lit lights.
Once home I check the voltage both at the battery and at the alternator, and I'm getting 13.5 volts at both spots, so its charging, from what I can tell.
The alternator is freshly rebuilt and before the work on the car, on a cold start, I was getting 14.2 V as the alternator, and 13.8 at the battery, but since I did some work on the car, I cleaned up the connections between the battery, starter and alternator, and now I get the same everywhere so at least the gremlin has been killed.
However before the work, I was not getting any dimly lit lights.
So today, I took the alternator out and replaced it with another one that I had laying around.
When I started the car, turned the lights off, the same lights were still dimly lit, but eventually they went out. When I turned the lights on, the lights that were off, now came back on but dimly lit. I can turn the headlights on and off and get the dimly lit lights to come on and off.
I've done nothing else to the electrical side of the car while working on it except for cleaning up the connections from the battery to the starter and then to the alternator.
Any ideas on where to start looking to get rid of the dimly lit lights? Do I need to replace the alternator????
Thanks in advance,
Matt
--
1989 - 245, 1990 - 245, 1991 - 245, and 1993 - 245
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Art and Phil,
I spent some time yesterday with the car while changing the oil in my son's 90' 240.
I replaced the alternator with one I was planning on rebuilding and all my lights are now out and the voltage level at the back of the alternator and battery are the same.
I'm not sure yet what happened to the freshly rebuilt alternator, which I and a friend of mine did, but my suspicion is that something in the exciter circuit gave up the ghost. I'll know more once I dig into it, but for now that can wait as I'm enjoying driving the car and now I have to prepare to work on my wife's XC70. Time to get the AWD working again!
Thanks for all of your insights. The FAQ was also helpful and has shed some light on area's I need to look at on this failed alternator, and things to look at when rebuilding my next one.
Regards,
Matt
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Hi Matt,
Thanks for the feedback cause it’s nice to know these things.
Art was right but when it comes to used alternators, grounds or connections one is going to get you.
I have an auto electric shop here in town. He spun the alternator for me out of my motor home because it was a dual output system all built into one. Coach batteries and engine battery.
He confirmed one side bad that was not working and gave me a price of $5 to $700 to replace it. He said most likely could be the diodes or windings.
A “Lester” name brand that he doesn’t repair because of those windings.
I decided quickly a tear down was in order.
I took him back to opened to the diode plate.
Some how he used an ohmmeter and found the one bad one and said one other one was weak.
I didn’t see his readings and I trusted him. Now it’s most of the time .... story to follow.
I knew one was out by using my ohmmeter but since he said he would change these two, I bought them from him @ $10 a piece.
$20 compared to a new alternator, I was very happy!
The story is this:
I had a brake rotor turned by one of his employees, sometime later, that didn’t get seated correctly in their brake machine.
Back at home on the car it wobbled on the front axle like .010.
I took it back to have it checked and the same employee had him come over to look at it on the machine. I couldn’t see through the doorway but they talked about it.
The employee came back with rotor and said it was fine. The owner heard me and told me it was fine as the employee left.
I knew what I saw had on the car and I asked him to depth mic. to the bottom flange where the rotor seats back up to the turned faces right there on the counter to see them not parallel.
He said he didn’t have any depth micrometers and parallels. Sorry!
I took it home and put the freshly turned side up in my lathe. The lathe is a little smallish to turn both sides parallel unless I do a lot of indicating in.
This way, I just turned only the inside seating area true, where the bolt holes are.
A little bit there throws the outer diameter out even more so it wasn’t that much out in reality.
I needed to go back and get something else and I talked to that employee.
I told him I have the rotor out in my car if he would you like to see what I did to it or Even check it.
He said no, of course, the owner walks around a lot!
But being the way I am though, I asked how he set it up and told him how it is suppose to work on the machine.
I advised him how crucial it is to get things mounted down “flat” on a clean surface . Don’t to rely on any spring loaded cones by themselves. Centering is not as important as being flat on the rear surface.
He took my advice to watch out for that too!
He is a good friend today, in a sly way.
I went to buy some brushes for my alternators.
He priced them in front of the boss, that was at the back of the shop.
He yelled back and said, those are a dollar. He sold me a set for a dollar and I bought several sets.
Of course, at the ASP company, I saw their site later that theirs are the same price. So, I got them at the owners cost, maybe?
I got my the rotor turning cost back at him a wee bit!
As they say, “What goes round (rotors do) goes around!”
Love to hear more about your results!
Thanks again,
Phil
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Ok, so I forgot to mention this.
Car cold: Battery reading 12.2 VDC
With lights off I'm getting 14.2 VDC at the alternator and battery.
With lights on I'm getting 13.9 VDC at the alternator and battery.
Any other thoughts with this new information?
Will continue to look at both Phil and Art's suggestions.
Thanks,
Matt
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Hi Matt,
I have been thinking more about that 12.2 voltage on the battery since my post this morning.
That voltage is really not good at all or you have an overnight drainage.
If battery is not accepting the charging from the alternator or the way to look at it is, the battery voltage is jumping up into the regulators range of shutting down the output.
There is almost no potential difference between the two systems where the battery is a constant systems “absorber.”
It’s always ready to dish out more than it needs back right away.
The alternator is only taking on all of what is on the load side of the cars system needs.
The job of regulating and it’s apparent “idiot light” is to watch over the control charge rate going to the battery.
So the battery is saying, “I’m fine” and the dim lit light or “dim wit light” is saying something is wrong by its only communication method.
The current is just tricking by, through the bulb.
Batteries are weird in like that when the base lead in them becomes so over oxidized it’s is closed off from its world inside there.
Cell phone batteries do the same thing and the charging times become shorter and shorter. Consequently, the up times fall and it becomes shorter and shorter until you need to keep it plugged in or replace the battery.
I think your car has this issue or a the possibility of large current drain.
Hook a meter up on the negative side in between the cable and the negative post with the meter set on milliamperes or auto range maybe up to ten amperes.
You want to see if anything is on that is not suppose to be.
You want the current to flow through the meter out to the whole car with everything off!
You should se 0.02 to 0.05 milliamperes for the computers and the clock together.
The VOmeter is like a big nose that sniffs out Gremlins. A load test done on the battery will tell you the recovery rate by watching voltage rise back on its on in like 30 seconds or less if it’s good.
Phil
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Some things to keep in mind when troubleshooting the charging system.
1. Don't assume it is turning at speed just because you don't hear the belt squealing. It doesn't take much of a film of oil to slip the belts or the rubber core of the harmonic balancer. And you probably won't be able to tell the alternator is running just under its loaded speed just by looking at it. An optical tachometer is needed to convince skeptics.
2. Remember when working correctly, the voltage depends largely on temperature taken at the regulator. 14.2 might be right cold, but then not right warm. Get a cheap voltmeter for your cigar lighter or dash. Costs less than the tip on a tow.
3. Having "freshly rebuilt" one may not be the same as having a properly performing alternator.
4. The blue ground wire at the alternator case can hide its faults pretty well. Don't depend on visual inspection. Double check by measuring the voltage drop when the trouble is occurring. Battery negative post to alternator case.
5. The D+ wire does not provide remote sensing for the voltage regulator in a Bosch charging system. Once a properly built alternator is charging, you can remove the D+ wire from the alternator, and the battery will continue to be charged at the correct voltage. However unlikely to be the cause of a fault, there are other uses in your 1991 car for this D+. It provides an indication to the ABS and SRS controllers that the engine is turning, as well as a path to ground for lamp test when not turning.
--
Art Benstein near Baltimore
“Let him who would move the world first move himself.” -Socrates
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Hi,
Well I think you are onto getting the car in good shape and making it reliable by cleaning connections. With that said, there are two halves of a circuit and in this case two semi-separate systems. Charging and Loads.
From what I can tell you are working over the charging system but you do not mention cleaning the grounds on the engine block and the condition grounding wire that goes from the engine block to the alternators housing.
These alternators are rubber mounted from two points on the bottom and the adjustment screw bracket sits on a rubber bushing. So basically it’s isolated.
There is a separate ground wire down there that goes bad!
In the instrument cluster there is a battery bulb light used to restrict exciter current going out to the alternators D+ side.
This is a small red wire that connects just above the big red battery wire and works with the regulator upon start up mostly. After a certain point these alternators become self exciting and monitor the systems load needs through the big red wire.
All of this is on the positive side of the cars “running down the road” electrical system.
The instrument cluster is on one ground (body ground on fender from battery) and the charging/starting system is on other explained earlier.
What I believe is going on is an imbalance happening during different loading moments.
The exciter wire with the light bulb is seeing a bad path to ground and “it may well be” on the body sides ground at the fender or instrument cluster’s ground side and that’s why you see the other lights glowing dimly.
If you look at a schematic of an instrument cluster light you will see diodes blocking a certain currents paths for each light either form the positive direction or ground direction.
That bulb is suppose to stay out and not burn if there is opposing voltage/current coming out of the alternator. So the bulb cannot flow current to ground through the alternator housing, this is normal.
Electricity loves to find “other paths” of least resistance.
So you think you ran the gremlin off, well let me tell you, corrosion is a gremlins favorite buddy when it comes around to electricity!
Diodes are pretty darn reliable but they can get weak so I start back with the negative side of circuits. It’s the simplest side as it has no moving parts! No switches and it is a whopping whole half of a circuit.
If you have one headlight dim, guess what, it’s probably a bad ground connection.
Technically, at the electron level, geeks say, “power flows out of the battery, into the system from the negative side! Go figure?
I wish a bank negative account worked that way paying bills!
Real bad weather storms, hurricane are created in lows pressure systems not the highs ones?
I tried blowing things off with compressed air from a nice low pressure tank, it just doesn’t seem to work!
Maybe they got things labeled backwards for us in grade school!
Come to think of it, that’s where I saw my first Gremlin character or was that a Gretchen?
Both were still green though, just like CORROSION is, so what’s up with that? Of all the colors for Disneyland to use, hmm?
I noticed you started out by saying “sages.” I had to look that up and I don’t know how it applies?
I must be from a Koda Chrome generation, as I think I learned a lot of crap in High School!
If I got any Wisdom together, it had to come over a “course” in the age of trial and error!
Try looking over a diagram of more ground points. The 1991’s points are like most of the other late cars in our manuals. There are some good illustrated pages somewhere.
Phil
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Phil,
Thanks for your reply.
I forgot to mention, that I did in fact remove the negative side from the engine to the battery and cleaned that up, and I also cleaned up the ground connections where the alternator mounting bracket hooks to the block, and its associated small wire as well.
So with that being said, are you suggesting I now need or should go through the rest of the ground connections one by one and clean them as well?
Ugh. Nothings easy, is it!
Thanks,
Matt
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Hi Matt,
In a nut shell that is what I was suggesting. There maybe a difference of ground potentials between the two systems.
I thought this way because I did not know if you had addressed that side of the cars cables.
There are two ground cable coming off the negative post. One goes to the engine block. As I remember it get nailed on top of an aluminum bracket for the accessories.
The other attaches straight to the fender well.
Check under the terminal and the ends of the cables for any signs of corrosion growing up under the insulation.
Yes there are other ground points and a place that a whole bunch are stacked together is under the instrument cluster down low. As I remember you have to remove the bolster or even ease back the center console cover.
The screw is on the upper left side. There are about five grounds placed on the one screw. It may be more to the left towards the ignition switch but I have found that screw slightly loose before.
From the factory it’s darn tight but these cars are not exactly factory fresh!
I don’t know exactly where the cluster gets it’s grounding point that why I suggested a chart.
You may also want to clean all the fuses in the fuse panel. I spray a light dusting of rust inhibitor up and down on those fuses after cleaning the tips and their associated holes in the clips. This leaves a on going vapor and film to repel moisture in that cold zone compartment of an outside door hinge. Water off wet shoes evaporates just high enough to go there.
To top that off the actual contact surface is very tiny on the clips as they are not cupped to fit the fuses ends.
On the 1991 and later, Art pointed out to me that the 25 ampere fused circuit was move into that panel, so, I make a more diligent effort to take care of all my cars fuse panels even more!
I myself keep all my cars inside out of my mild weather scenarios. My cars are also living a retired life.
I can only imagine what other cars look like if left exposed to harsh weather conditions at work and on salted streets.
So with that said, I want to be optimistic that you shouldn’t have to find ever one of them. Only you know what things look like, in general, so it’s your call!
I just read Art’s post about variances in the rebuilds of alternators. I have to say I get JY ones but try to be picky and I inspect the brushes and slip rings before using.
It appears that the alternator is working fine but that rest voltage is too low!
How old is the battery? 12.2 is nearly depleted.
So hope you have enough information, so your thoughts will conquer all!
Phil
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