Charging system - Page 2 - PeachParts Mercedes-Benz Forum

yellowbenz · #16 08-09-2008, 11:47 PM

It should be 14+volts. I don't think it is charging.

compress ignite · #17 08-10-2008, 12:15 AM

BBBOOMER,

You've "tagged" the Alternator correctly , it's marginal.
But,in a lot of cases the spec Alternator for these cars isn't a Barn Burner
to begin with.
Yours is giving it the Old College Try...at idle with all the junk loading it up
it's low... BUT it recovers with RPM.
You might look into an Adjustable Voltage Regulator (I don't know if anybody
makes one for your Alternator)

GSXR has had great success with retrofitting some of his Mercedes with
143 and 150 Amp Alternators.

Read about it here:
http://www.peachparts.com/shopforum/showthread.php?postid=444946

bbboomer · #18 08-10-2008, 01:20 AM

Compress,
Interesting info on the alternator upgrades but I don't think I need that much added juice. I don't have any additional amp/volt consumers.
After mulling this over and over and over and... well you get the picture.
I think the problem may be related to the delay before the alt begins charging. My thought is the delay is not normal and is probably being caused by resistance. I know the gp relay will show a delay in charging because of the high draw it causes but it clearly cycles off and still there is a considerable delay before the alt begins to produce 13.5 volts.
I think I will check each wire + or - from the alt to the battery for resistance. I have checked their terminations for corrosion etc but not the wires themselves.
The positive wires from the alternator are joined at the junction block with the feed wire continuing on the the starter and then to the battery cable. If I conect a jumper cable from the pos wire at the junction block to the pos battery cable that should overcome any resistance in any of the cables. Do you know if that will smoke anything? I don't want to burn the ole girl down in the driveway!
Also do you have any info on what the gp relay should be pulling or what I should check there?

Diesel911 · #19 08-10-2008, 01:26 AM

If it would not be that you have checked I would say that the belt/s were slipping on the pulley.
This is a situation where an inductive Amp Meter would come in handy. It takes a reading from the magnetic field around the wire. You slide it over the wire and do not have to wire the meter in series with the circuit you want to measure. The problem is I have not seen them in any of the local auto part stores.
The idea would be to find out if your alternator is maxing its amperage out put. If it is maxing the amperage out put and the voltage is low it may be the Alternator is doing the job but something is using up the voltage.

Diesel911 · #20 08-10-2008, 12:20 PM

I came acrose this:
ANOTHER QUICK CHECK FOR BOSCH ALTERNATORS
http://www.aa1car.com/library/2002/cm10220.htm
One way to check the integrity of the alternator and diodes on Bosch alternators is to check the voltage readings at the D+ (blue wire) terminal and B+ terminal. The voltage reading should be the same at both terminals. A difference of more than one volt would indicate faulty diodes and the need to replace the alternator.

B+ goes to the battery so what ever the batter voltage is while the alternator is running is that reading.
To take the D+ you will need to connect the (+) probe of the Voltmeter to the blue wire with the blue wire still connected to the Alternator and the (-) probe to ground.

Jeremy5848 · #21 08-10-2008, 12:33 PM

Quote:

Originally Posted by bbboomer

. . . I installed the battery and checked the amp draw. This is interesting, it had a 3.5 amp draw when I first installed the battery which dropped to about .2 amps after a few minutes . . .

I'm not familiar with the SD electrical system. Doesn't it have an electrically-operated vacuum pump hidden away somewhere? Could that be the 3.5A load you mention?

A load of 200mA continuously with everything turned off is too much. It will drain the battery eventually. The clock circuit, radio memory, etc., should use no more than a few milliamps. Anything more is a problem of some kind that needs to be found and fixed. See if you can find it by pulling fuses, as previously suggested.

It's also strange that there is a delay before the alternator begins charging.

Jeremy

bbboomer · #22 08-10-2008, 03:23 PM

Okay I hooked up a jumper from the pos wire at the alt juction block directly to the bat pos post. That should have eliminated any resistance in the any of the pos wires. There was no change, the alt still has a 1 to 2 minute delay before producing full output at 13.8 volts. It did maintain 12.6 after the gp relay cycled off till it kicked up to 13.8.
Does anyone know what can be checked at the gp relay and what the specs should be? What all does the relay control?
I found a replacement ($250) but it list several things it controls other than the glow plugs. Is this the case, the gp relay controls several things?
Could the regulator be causing the delay?

yellit · #23 08-10-2008, 04:33 PM

Have you tried adding grounds yet...?
Might want to ground alt frame directly to neg batt. term to eliminate that potential problem....also check voltage drops between all ground junction areas with DC meter on low voltage scale....with full load on system....One forum fellow had a bad transmission to frame large ground cable that was causing this exact problem.....that was on a 123 series....at least rule out ground path problems since the alt checks good on the bench test....

bbboomer · #24 08-11-2008, 01:16 AM

Well I am just about out of ideas.
Connecting the positive side jumper made no difference, so I am going to rule out resistance as the cause for the charging delay. I have tried a jumper on the ground (alt to bat) that didn't help.
I saw on Fastlane there is a glow plug relay that has extended heat time. That may explain the delay before seeing full charge voltage but I think mine is the stock Bosch unit. Anyway, when the relay cycles off it is clearly visible on the Fluke but there is still a delay after that before it begins showing full output. I wish I knew what to check on the relay so I could rule it out.
This one has really got me stumped boys.

compress ignite · #25 08-11-2008, 01:34 AM

1.The Glow Plug relay ONLY controls the Glow circuit (5 or 6 Glow plugs)
If you don't have the relay that has the AfterGlow function(It still warms
the plugs up to 120 seconds after engine start) the Glow Relay isn't
stealing current.[I wonder if the Alternator is taking those few seconds
to ReCover from the "Glow Cycle" (Reaching for Straws,here)?]

The Glow Fuse inside the relay is rated @ 80 Amps...It takes Mucho Power
to "Smoke" those Glow Plugs.

I like the Bosch test Diesel 911 offered.

Actually,I know when I'm beat...It's time for the Heavy Guns.
Aurthur Dalton,SteveBFL,MB Doc

bbboomer · #26 08-11-2008, 02:02 AM

Compress,
Pretty sure I checked that already but I will do it again.
I found a link here that talked about a 120 amp alternator purchased from an E-Bay seller. It is supposed to be a straight across swap except for the wire harness and it comes with whichever pulleys you need.
I shot the guy a message to confirm and I may go that way if I can't find the problem pretty soon.
Mine checks okay although on the low side of okay. I would normally accept that if it weren't for a dead battery leaving me stranded at the market.

compress ignite · #27 08-11-2008, 02:20 AM

I do comprehend.

AD and all the other East Coast Techs do not start their day quit this early...
'Give them until Noon or so to "Find" this post.

If it has ever occurred before,they'll have it's name!

yellit · #28 08-11-2008, 06:40 AM

If your alternator has the little brush/regulator unit on the rear of it ....might want to swap that device out to see if it makes any change in charging operation........Quick & easy.... I think you can change it withthout removing the alt....I have a couple of those if you need me to send you one to try....or if you need one fast... junkyards or any parts store can get pretty quick....I assume you have tried another ground cable between frame, engine block & and negative post....

bbboomer · #29 08-11-2008, 10:15 AM

Okay,
Standing by for the charging system wizards.
I have checked and done all I know to do and everything that has been suggested.
I do not know what to do now.

bbboomer · #30 08-11-2008, 07:30 PM

No charging system wizards out there?
I could sure use some fresh ideas!!!