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1983 240D, 2002 Sprinter
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9 Posts
Discussion Starter #1
Just thought I'd post this to help out those who may end up having the same experiences as me.

About four years ago my 240D's alternator gave up the ghost so I picked up a rebuilt unit from my local auto parts place and of course opted for the lifetime warrantee. About a year later my glow plugs needed to be replaced so I did that and decided to also replace the glow plug control unit just for good measure. About a half year later my alternator began to fail... charging dropped to 12.3 volts at all rpms and dropped to 11.1 whith the headlights and blower going. So I went to my auto parts place and exchanged the alternator but also had them bench test the 'new' one... it checked out fine. I installed it, started the car and checked the charging system... although it took about a half a minute the charging voltage rose from 12.3 to 13.9.

During the last couple of years I ended up having to replace the alternator 5 more times... of course neither I nor the auto parts place were very happy about this... they felt my car's wiring was faulty and I felt their rebuilds were of poor quality (I speak from experience with Chinese manufactured electrics such as voltage regulators and diodes). Just recently my 240 started showing signs of the alternator failing again. I finally had the time on my hands to go through my cars wiring harness. I tested wires, cleaned terminals... nothing out of the ordinary was found and no improvements to the charging rate resulted. I remembered reading elsewhere that a person had charging problems with their W123 and he would hit his glow plug control unit and the car would suddenly charge as normal. Well I decided to pull out the old unit I replaced a few years ago and hooked it up. I started the car and was surprised to find that my charging voltage immediately jumped to 13.9 volts... no lag as has been the case the last couple of years. I turned on headlights, fog lights, blower... the voltage only dropped to 13.7 volts. My car was charging like I remember her doing years ago.

So, a brand new Bosch glow plug control unit seemed to have been defective and would put such a strain on my charging system that the voltage regulators would eventually burn out prematurely.

Just food for thought.
 

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1984 300D
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5,070 Posts
I saved this thread in my notes.

Looks like you also proved the words to the effect; if it is not broken don't try to fix it; concerning the Glow Plug Relay.

For others if you pull out the Fuse that goes to the Electric Clock in the instrument cluster and remove a Battery Cable and put one Probe of your Voltmeter on the Battery Terminal and the other on the Cable you remove you can see if there is anyting conducting.
 

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1983 240D, 2002 Sprinter
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9 Posts
Discussion Starter #3
Looks like you also proved the words to the effect; if it is not broken don't try to fix it; concerning the Glow Plug Relay.
IMHO, replacing something that just may have been an original component on a car that is more than 25 years old with more than 350,000 miles sounds more akin to preventive maintenance. ;)

What I have learned is that these days I cannot even trust a brand new Bosch component. That's a very sad realization indeed.:(
 

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W-1-2-3 Go!
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16,161 Posts
IMHO, replacing something that just may have been an original component on a car that is more than 25 years old with more than 350,000 miles sounds more akin to preventive maintenance. ;)

What I have learned is that these days I cannot even trust a brand new Bosch component. That's a very sad realization indeed.:(
How long ago has the "original" (or "old") GP relay been there?
 

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1983 240D, 2002 Sprinter
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9 Posts
Discussion Starter #5
It's been a few days since I put the old unit back in... no idea how old it is which is why I replaced it to begin with. The car's electrics work better than it has in years... especially at night.
 

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Daily Drive 82 240D 4 speed
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291 Posts
alright, so this is an interesting topic for me.


I've recently been having charging issues. I'll start the car up. Everything is dandy.... turn on the headlights and blower and the radio turns off. Step on the gas so the alternator is going, and it comes right back on. Till i get to a red light, and the radio goes out again. So i turn the blower off while at a standstill radio comes back on.

So im not sure whats going on there. Battery was ready at 12 or 13 point something volts i believe. I decided to check just for the sake of it, the cigarette lighter, and that was jumping all over the place. 10, then nothing, then 13, then 5 volts. It was all over the place.

Any thoughts on it? Alternator? Voltage regulator? or your weird relay issue?
 

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1983 240D, 2002 Sprinter
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9 Posts
Discussion Starter #7
I would check that the belt is at the correct tension. A belt can slip yet not give any audible indication. That's probably why your charging system voltage is high enough to power the radio once you remove a fairly heavy load like a blower motor. However, if your radio goes out I'm guessing that your voltage is dropping to about 10volts or even lower... an issue caused by more than just a slipping belt alone. Also, if I'm reading your response correctly, I wouldn't trust any voltage readings at the cigarette lighter socket... only at the battery terminals.

Check readings at the battery with the car at idle with radio, fan lights, basically everything turned off. Then increase engine speed and note the voltage. Then start adding a load to the charging system noting the voltage every time something new is turned on. The headlights and blower motor will probably cause the heaviest load but IMHO with a healthy charging system you should only see about a .2 volt drop.
 
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