Electric wizards needed. 1984 300D - Page 2 - PeachParts Mercedes-Benz Forum

renman · #16 11-28-2007, 01:05 PM

Quote:

Originally Posted by Brian Carlton

Why is it so difficult to connect the ammeter in series with the negative battery terminal and report back with results?

Disconnect the negative cable.........put one lead of the ammeter on the cable.........put the other lead of the ammeter on the battery post............read the ammeter...........post the result.

We already explained that voltage readings are not relevant to this issue.

he battery is not taking a charge, nor receiving a charge according to the volt and amp readings using the clamp meter between the alternator and battery post. The battery went from 13.8 something to 12.31 volts within a split second. Why is this irrelevant?
Here are the readings.

With the clamp meter set at 4A I hooked the DMM between the negative cable and post. Here are the readings.
The very first was 0.158
Immediately after was: 0.024
All subsequent reading are 0.049

Brian Carlton · #17 11-28-2007, 01:12 PM

Quote:

Originally Posted by renman

With the clamp meter set at 4A I hooked the DMM between the negative cable and post. Here are the readings.
The very first was 0.158
Immediately after was: 0.024
All subsequent reading are 0.049

Can you explain what's going on here? Are you reading amps?

Is the meter accurate and why is it fluctuating with time?

If accurate, the reading of .049 is acceptable if it's actually reading in amps.

I've never been a fan of digital meters............

renman · #18 11-28-2007, 02:12 PM

I changed batteries in DMM and went out and rechecked. Why the fluxuation? I was hoping someone would tell me. Here are readings:

DMM set at 4A with black lead to post and red lead to negative end. Three readings 0.116,0.122, and 0.121

DMM set at 4A with red lead to post and black DMM lead to the cable end. 0.076 and again a few minutes later it was 0.083

The previous readings from post #16 where done with the black DMM lead to the cable end. Which where 0.158-0.160 then 0.024 then 0.049 after that.

LUVMBDiesels · #19 11-28-2007, 02:13 PM

Check the Alternator wiring again...

You should have run the heavy line from the thick short lug on the alternator to the post on the juction box where the original output wires were connected. You then run a smaller gauge wire from the thinner longer lug to the post where the small blue wire was connected on the junction box. I ran into similar wierd things until I got this right...

Brian Carlton · #20 11-28-2007, 02:18 PM

Quote:

Originally Posted by renman

I changed batteries in DMM and went out and rechecked. Why the fluxuation? I was hoping someone would tell me. Here are readings:

DMM set at 4A with black lead to post and red lead to negative end. Three readings 0.116,0.122, and 0.121

DMM set at 4A with red lead to post and black DMM lead to the cable end. 0.076 and again a few minutes later it was 0.083

The previous readings from post #16 where done with the black DMM lead to the cable end. Which where 0.158-0.160 then 0.024 then 0.049 after that.

Time for a different meter.

Flawed data in.........bad diagnosis out.

Use an analog meter...........they don't fluctuate depending on how they feel at that moment...........

JimSmith · #21 11-28-2007, 03:27 PM

Quote:

Originally Posted by LUVMBDiesels

Check the Alternator wiring again...

You should have run the heavy line from the thick short lug on the alternator to the post on the juction box where the original output wires were connected. You then run a smaller gauge wire from the thinner longer lug to the post where the small blue wire was connected on the junction box. I ran into similar wierd things until I got this right...

I am in this guy's camp for the moment. You have done something to the alternator to battery wiring, and now have an unexplained performance issue. I would strongly suspect it is the wiring, and there is a chance you have fried your voltage regulator in the process.

The digital meter is telling us something. Let's not ignore it. Most of the reading changes that have been posted are nearly meaningless and on an analog gizmo would be ignored because they couldn't accurately be identified. In the cases where the differences are significant, I doubt the measurements are not real. So the question is what causes them?

If the drain of the battery is normally around 50 to 100 milliamps, what causes it, and why is a range "normal?" I believe there are some vehicles with alarm systems and others with no more than a clock running. Some older cars have clocks that run intermittently. If 50 to 100 milliamps covers these loads, and explains the range, we need to understand if the alarm system load is intermittent or constant, or if there is another "leak" causing the variation in readings.

I think the more frustrating aspect of this particular case is the communication. The way the current draw with everything shut off was supposed to be measured was not followed, and instead a sensor designed to work with higher current levels, it seems, was used. Part of the problem dealing with the information is that it has been gathered using a method that the person providing the instructions, and presumably the experience to interpret the results, is not familiar with and therefore is not comfortable with the data. It might help getting a useful response to follow the directions exactly and report back the results. Unless, of course, your multimeter is not suited to make the current measurement the way Brian described it.

It might be interesting to note the current levels between the alternator and the battery when you are running with various loads (blower, lights, windows, etc.) applied. Especially after starting.

I would start with a very thorough review of your wiring of the new alternator and the various changes. You might post a sketch of exactly what was done, a kind of "as-built" version of your electrical system charging connections. We can then see if there is anything peculiar that is escaping your scrutiny.

Good luck, keep at it and I am sure you will figure this out with some help from this crowd. Jim

John Schroader · #22 11-28-2007, 04:16 PM

Finally here's an area in which I have some expertise. First, a digital meter tends to be more accurate, plus if it is hooked up backwards (wrong polarity) it simply gives a negative reading. An analog tries to push the needle backwards. From what I've gleaned from this discussion, it sounds like the voltage regulator is not functioning properly. Another consideration that has not been mentioned that might apply to the alternator in an MB is a leaky diode in the alternator. I have seen diodes (rectifiers) break down and let the battery drain when the the key was turned off. The battery and alternator are generally wired in parallel and the only thing that keeps the alt from draining the battery is the rectifiers (diodes). If one becomes leaky, that can surely allow the battery to drain when there is no leak elsewhere. But ----- in one of these messages, I think I recall a voltage in the high 12 v range with the engine running. Should be more like 14v. A car battery produces 12.6v on its own.

renman · #23 11-28-2007, 06:57 PM

Now, If I seem a little frazzled and goofy, I am. I thought this problem was behind me.In the meantime I have been working on my project 300SDL. In the last 4-5 weeks I have fixed the following electrical problems. Seat motors in both drivers, and passenger seats, diagnosed and replaced passenger side control box for power seat, diagnosed and resoldered trashed wiring harness to seats (front), replaced three doors switches, repaired two window lift motors, fixed power antenna, installed new head unit, installed new amp and rewired for speakers, climate control unit, and miscellaneous electrical repairs. I still have one more lift motor to sort out and whatever else needs fixed, I don't know about. Oh ya the sunroof, temperature switch that keeps the radiator fan running and some jack legged attempt to repair the air conditioning, and whatever else.So how about a little slack. I don't even like doing electrical repairs, I usually end up figuring it out, and it works, but Lord knows this is not forte. Sorry again for the miscommunication and bad info.

TODAYS AMP ELECTRICAL READING AT THE BATTERY:
They where all wrong. Sorry. I called the DMM company about the #687 low current probe/DMM. I was told that the probes where not suppose to be used to measure amps; only the clamp on will measure amps. So I went back out again and using both of my DMM to measure ma I came up with a reading of 0.056ma draw.

MY WIRING CHANGES.
ALternator
All I did was add one additional wire from the AL129X alternator main lug to the positive side of the battery. That it. When I put this alternator in I checked with what I was suppose to do by e-mailing and corresponding with guys on the forum. I was told to leave the existing wiring alone and intact and just run the additional wire to the battery from the starter. I also did personally speak with the tech at California Alternator and Starter who told me the same thing. Remember there are only two wires and two lugs. Now it has been suggested again in this post and in the previous post I deleted, that the original wiring from the alternator main lug goes to my junction box next to my battery. sorry, but it goes up the fender well and runs up under the battery tray. It does not go to the starter, battery, or junction box, as some have suggested. Other than checking my grounding straps for integrity, thats it.

AMP DRAW AT FUSES
If I did this correctly the amp draw on #A fuse and #2 fuse is 02.07 ma each. Otherwise its zero on all other fuses.

So my alternator is probably fried, WHY OR HOW DID IT FRY? and I still have a battery drain, Great.

myarmar · #24 11-28-2007, 07:16 PM

If you using the meter pictured it cannot measure current with the leads. You have to use clamps around the wire. Also, I'm not familiar with this model, but usually clamp meters are not going to give your meaningful readings for low mAmps.
Mike

renman · #25 11-28-2007, 08:08 PM

Quote:

Originally Posted by myarmar

If you using the meter pictured it cannot measure current with the leads. You have to use clamps around the wire. Also, I'm not familiar with this model, but usually clamp meters are not going to give your meaningful readings for low mAmps.
Mike

See above post # 24. I am using an additional DMM in additon to the one pictured,yes I found this out today that they don't work with probes.

renman · #26 11-28-2007, 11:32 PM

TAKEN FROM THE ALT129X POST
post #153
Nate said:
All you needs do is run a new wire from the output buss on the alternator to the positive terminal of the battery .

Your new alternator isn't going to be putting out 115 amps all the time unless you have rally nights and /or a 350 watt stereo .

An alternator only puts out what is demanded of it , not it's full rated capacity constantly
.
__________________
-Nate

post #156 GSXR said:
It's perfectly fine to add an additional (heavy gauge) cable from the new alternator to the starter cable, and leave the existing cables where they are. If the existing cables are the blade-connector type, you can cut off the blades and crimp/solder on a ring terminal, and connect it to the B+ terminal also. There's no problem with two parallel outputs from B+ (one to the starter, which goes to the battery; and the second being the original pair of dinky wires to the junction block).

Dave

Post #174
Just Installed Alt 129x
I spent most of this afternoon replacing the stock 65 amp alternator with the 115 amp bosch I received by UPS from the California alternator store. All in all not to bad a job. I took my time and will button everything up tomorrow afternoon. I left the stock wiring intact and ran upgraded wiring. While I am at it I am also checking all of the ground cables.Thanks to everyone for all the above help in making this upgrade happen.

__________________
Cliff D.

Where do I go from here?

BoomInTheTrunk · #27 11-29-2007, 12:48 AM

alright just to make sure you wired everything up correctly lets just go over things again. ok my car has the same wiring as yours does in that there was no junction box on the fender and that the wiring went up into the firewall back behind the blower motor and who knows from there. So did you somehow splice into the excite wire on the plug (that is i believe the Blue wire) this blue wire is what goes onto the smaller bolt on the alternator. In my case i just ended up cutting the plug off entirely and just putting ring terminals on the two 10 gauge wires and running them to the main post on the alternator. I also ran a heaver gauge wire to the battery. Im not sure but those wires left on the plug may go to something and stop the drain, just a guess. This is how mine is wired.

I think that you are going to have to cut off the plug because you have no junction block on the fender to run new wires to. so cut off the plug about 2 inches from the plug so if needed you can put it back on. then put ring terminals on those wires to the main plug.

The small red wire is just the blue wire extended hope that this may clear up a problem. sorry about the angle only one i could get because it was dark out.

renman · #28 12-02-2007, 05:18 PM

TWO PART POST HERE IS WHAT MY GLOW PLUG RELAY LOOKS LIKE.

Here are pictures one from the glow plug relay out of my 1984 300D. I was going over the car looking for shorts and general maintenance, most related to finding the cause of my battery drain problem.

Picture #1.
Shows the glow plug relay @ the terminal strip lugs. The phenolic plastic or whatever it is around the terminal lug is entirely cooked/melted. An interesting note is that the terminal strip fuse was not burnt or damaged visibly although as I was beginning to clean it, one end broke off.
Picture #2.
Is the glow plug relay board indicating damage to the circuits. One spot is indicated as almost burnt through.
Picture #3. Is the opposite side of relay board with more damage.

The car doe's start right up even with the internal damage to the relay.
Question #1. Can this be draining my battery by shorting out internally or staying on after it should have turned off?

renman · #29 12-02-2007, 05:41 PM

While my car is up on ramps looking for possible electrical problems, I went ahead and decided to replace the shifter bushings, transmission filter, fluid, and the green modulator valve on the drivers side of the transmission. At first I didn't even notice the bare wire leading to nowhere until I pulled the plug harness from the transmission.

Picture #1. The wire shown was in the original plastic sheath, not added on the outside, so I presume it went somewhere. At present it is taped up and insulated. As best I could the tell the end was rubbing against the transmission.

Picture #2. I was tracing the wiring harness that comes out of the alternator, up the wheel well, and disappears under the battery tray. I pulled the battery tray and noticed the brake electrical wires going through the grommet in the wheel well where barren also. Another potential ground short. I stripped the wire back taped the bare wire and shrink wrapped the cable until I can install a new one.

barry123400 · #30 12-02-2007, 05:51 PM

A shakey or damaged glow plug relay coming on intermittently could certainly take down a fully charged battery quite easily overnight. I was speculating about this as your problem in my mind while reading earlier portions of your thread. Having the intermittent high drain with the ignition key off does limit the possibilities of the source of the drain as well. The glow circuit through it's relay has a direct path to the battery available to it at all times I think.
If you can disconnect the relay after every use it should either clear or condem it. Just re hook it up prior to glowing the car and disconnect it once car is started.
Sounds like you need a pick and pull or other unit anyways since the high current from age or being on far too long has done a number on it.
Again since you had the problem before and it persisted even after your changing things out it is a very good place to start. Most other leakage failures would not have the intermittent component you experienced. Let the posters on the site know how it works out.
I would forget the alternator for now anyways as a leaky diode never clears itself temporarily. Or only leaks intermittently so to speak. A diode technically can become intermittently open and restore itself to function. But intermittently leaky because of its type of solid state construction and how it actually functions s a real reach.