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Old 11-22-2006, 09:07 PM
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unkl300d unkl300d is offline
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Join Date: Jul 1999
Location: San Francisco, Ca
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Question W123 electrical -

Hello and Happy Thanksgiving!

I have gone through the archives and gleaned alot of good info.

Until my car battery recharges, I am submitting these questions for extra tips.
1979 300D. 163K miles. Garage kept. No water/rain interaction this past week.
When running, a multimeter reading shows 13.8 volts at the battery terminals with engine at higher than idle revs.
Seems like alternator is good. Archives confirm 13.8 volts as adequate. (Alternator is a Bosch 005-154-98-02 88 remanufactured replaced June 1995 at 110,825 miles).

I replaced the battery on Sept. 19 2006 with an appropriate Interstate battery. The old one lasted about 7 yrs. So battery is new.

Yesterday my car's battery was very low. (11. volts.approx)It had enough juice to keep the clock working and interior lights. Car would not turn over at all though. I jumped it and the car started easily but I shut it off after 2 minutes because I had no time to do a freeway run .

I also made sure that I turned off the radio properly thinking that I may have accidentally activated a stanby mode which may have drained the battery since last used 2 days previous.
Tested the trunk switch and light. It works and bulb was not hot to indicate it had stayed on.

~Discovered glove box light did not work. Removed the bulb and the bulb filament looks whole but untested yet. Yet to remove the glove light switch to inspect. Forgot to look at cig lighter.

Both front and rear interior lights work but the switch that activates the rear int. light does not activate the light. Other accessories on that dash panel not tested at that time.

Used contact cleaner on the alternator connections and general area.

Today I tried to jump start. Did not start. Battery read about 2.3 V with multimeter before jump.
After leaving jumper cables on for over 5 minutes with other car at fast idle, still could not start the 300D. Not enough juice to activate starter. Seemd to want to go.
I tested battery with jumpers off. Tested around 11.7 V (as a result of recent boost). After about 20 minutes it went to about 2.3 V

~ I noticed that when I took a multimeter reading of the battery terminals intact with battery cables, the reading was about 2.3V
When I removed the neg. battery cable and placed the meter terminals onto the battery terminals (pos terminal still connected to pos cable) the reading was about 6.8 or 5.8V. It went up.

~~So, is this normal that the negative cable will cause a lower reading of the battery?

I inspected the battery cables as best as possible. No visible evidence of bad.

I could not yet locate the ground wire from engine block to chassis.
~~Where is it?

~~ I read that the grounding of the alternator should be checked. Where is that?

As soon as the battery recharges- it is on a charger... slow... I will do the ammeter on series and individual fuse tests as per archives.

I already remioved the glove box light/radio fuse today. just to remember that this may be one source of a leak.

Also could the alternator brushes still be suspect?? If so how to know if my alt. has the replacable ones?

By the way, the battery cables were clean and tight previous to any dinking around after the fact.

Any insights at this point or tips, opinions???
When last running, all basic functions seemed to work.

Thanks

Denis
__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

Last edited by unkl300d; 11-22-2006 at 09:16 PM.
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