So I have a 1992 300D that I bought recently it has the 2.5 om602 it has 237xxxmi drove it for a week no issues then it started. Have a couple batterys around tried them didnt help. Read up on the voltage regulator replaced it, it was super worn down but still no change. So I bought a volt meter with the car running im getting like 12.3 but heres the weird part I disconnect the positive with it running (which I was told I shouldnt do, did it anyway) but the volt meter shows 14.2 at the positive cable when disconnected from the battery. I have cleaned up every contact and ground including the ground strap from the trans to body. The alternator seems to be working the battery just isnt taking it? Has to be a ground I missed? Also I have no tach or cruise control could my OVP be this issue? Please help I drive for 15 min after charging with a battery charger and lose everything wipers, headlights ect. Help!!!
1992 300D Charging Issue
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No output from the alternator tells me that the problem might lie in the ignition switch.
No tach "could" be OVP, BUT you need to have a functional charging system first.
Without at least 13.5V to no more than 14.5V, the bird is dead.
No tach "could" be OVP, BUT you need to have a functional charging system first.
Without at least 13.5V to no more than 14.5V, the bird is dead.
Never had any issue starting it as long as there is enough charge to start it. But like i said above with the car running and positive disconnected it stays running and puts out 14.2. When I connect the battery again it only puts out whatever charge it has in it around 12.3 which is low and slowly drains depending on whats on fans, lights, ect. I know it should be like 12.6 to 12.8 but when I put the battery charger on it I see an increase in voltage on the voltmeter and do not when I have it connected and the car running. I wanna say its a bad ground but when im getting 14.2 with the positive disconnect and car running im putting my negative lead from the meter to the negative post on the battery so theoretically my ground should be good right? Just doesn't make any since to me
Bizzarro. Just be aware that that ignition switch is responsible for completing the D+ circuit which sends the green light to the alternator to start charging.
Another thing, on a diesel you should never be able to run the battery down after just a few minutes since there is no ignition system.
Almost sounds like the alternator is hooked up backwards and is DIScharging the car.
Just doesn't make any sense.
Another thing, on a diesel you should never be able to run the battery down after just a few minutes since there is no ignition system.
Almost sounds like the alternator is hooked up backwards and is DIScharging the car.
Just doesn't make any sense.
It never dies! My drives are normally anywhere from 15 to 30 min. Ive been charging it everytime I go some where until I figure it out. But as it loses voltage I lose everything even turn signals (had to do the ol fashion arm out the window a few times lol) but it stays running. Ive checked the voltage after a longer drive after losing everything and it was down to about 8.8 volts and still running gotta love diesel! As it loses voltage it also loses some performance.
My top 3 suspects are wiring fault(s), bad alternator, bad ignition switch.
I highly doubt ground straps is the root cause. Symptoms don't fit/smell of a ground issue.
A typical ground problem would be if the headlight dims when you put on the blinkers.
I highly doubt ground straps is the root cause. Symptoms don't fit/smell of a ground issue.
A typical ground problem would be if the headlight dims when you put on the blinkers.
Is there a way to test the ignition switch? Also an update replaced my battery didnt fix anything but my old battery wouldnt hardly take a charge anymore at least I can get around for now. But after replacing my battery my tach would come back intermittently along with the abs light going off when the tach would work. The new battery had 12.9 off the shelf. With it in the car still stayed at 12.9. Went for a 40 min drive and tested it after I got back and shut it off it was at 12.7. The tach quit working all together toward the end of my drive so im assuming that the tach and abs need around 12.8 to 12.9 to work.
As I stated before, the electronics need at least 13.5 to fully function. Even on my 95 diesel with a perfect charging system, at first crank of the day engine fires but tach does not come alive/register until about a second later.
Stop focusing on the tach, and keep your attention on the charging system and why/how/what. The tach is 2nd least useful gauge in the entire car, so much that the tach was an "option" on euro spec W124 diesels and even lower end gasoline models.
As far as testing goes, not much of a way to test it other than trying to wiggle the key in position 2 (after engine is running) and have a helper see if anything between 13.5V and 14.5 V shows up at the battery terminals.
Stop focusing on the tach, and keep your attention on the charging system and why/how/what. The tach is 2nd least useful gauge in the entire car, so much that the tach was an "option" on euro spec W124 diesels and even lower end gasoline models.
As far as testing goes, not much of a way to test it other than trying to wiggle the key in position 2 (after engine is running) and have a helper see if anything between 13.5V and 14.5 V shows up at the battery terminals.
Is your charging light showing up at start up ? If not the bulb in the speedo will need replacing No light from charging bulb . Then it fails to chargs the battery up...
Ok I will try that. And this is my first mercedes so not very familiar with them. I read that theres a possibily that i could have installed the regulator wrong or it could be the wiring at the alternator? But I dont think that could be it since im getting 14.2 with the positive disconnected and running. Also read that the battery light is part of the alternator circuit and if its bad it could be the problem. All of the dash lights come on including the battery light when I turn the key on, but when my voltage gets low even at the 8.8v I read the one time the battery light never comes on. When is was raining one time after driving for a while my voltage was low abs and srs lights were on and dim but they would randomly get brighter like a loose connection somewhere. Im leaning toward wiring somewhere im gonna take the day tomorrow to check the wiring at the alternator and battery light. Anyways I greatly apprecate all of your insight! And ill post my findings later on tomorrow.
Roger that. Don't pull your hair out just because it runs. Remember, it's a diesel hence no ignition system.
You could disconnect every electronic component and it will still start and run as long as the pre glow relay and ignition switch are hooked up.
You could disconnect every electronic component and it will still start and run as long as the pre glow relay and ignition switch are hooked up.
Trevor the battery light comes on when I turn the key on but never comes on when my battery gets low my srs airbag light comes on but not the battery light. Also tried wiggling the key while running with the voltmeter hooked up with no change.
Its a refurbished alternator it says it right on it. Ive only had the car less than a month so no telling how long ago that was but from how dirty and stuff it looks like its been in there for a while. And i completely removed the ground strap going from the bellhousing to the body cleaned it (was super dirty) and cleaned and sanded all the contacts on the strap and the car. I have a question im getting 14.2 volts at the positive cable with it disconnected from the battery and running but is there a chance that the alt is old and warn and putting out good voltage but not enough amperage?
Ok went out to walk the dogs and have a smoke and decided to check the voltage with the positive off the battery with the car running again and now im only getting 11.9 to 12 volts at the positive. Ok so I guess I should have mentioned this but when I bought the car some dumbass cut the thick red positive cable going to the battery right about in the center of the firewall I tied into it with a thick positive cable from my boat soldiered it wrapped it in electrical tape and put a hose clamp on it see attached picture lol im thinking thats the problem now didnt think so at first cause I was getting 14.2. But im gonna replace the whole cable to eliminate that as the culprit. Will post more tomorrow pretty much dedicating tomorrow for car repair.
Attachments
The battery area never drains out untill the car is moved .So get a good paint on protective wax and go mad inside there .And dont think about drilling a hole in there because it will only drain out in to the foot well . There is drain hole where the rubber drain pipe goes in to .But the rain water holds in the pressed depressions in the steel bodywork ..
Hi
I suspect from what you have posted that you have a diode on one phase open circuit
that would mean you would get 14.2 volt with the battery disconnected as you are not pulling any current.
When you connect the battery their would be no Output Current And the voltage would drop to Battery voltage and continue to discharge.
Hope this Helps
Comrob50
I suspect from what you have posted that you have a diode on one phase open circuit
that would mean you would get 14.2 volt with the battery disconnected as you are not pulling any current.
When you connect the battery their would be no Output Current And the voltage would drop to Battery voltage and continue to discharge.
Hope this Helps
Comrob50
Will look into cleaning and fixing the water in battery area never even knew that was an issue with these cars. And Comrob where would I look for said diode? And have to say thanks again you guys are awesome! As my benzworld account says im a newbie hahaha
Also just found something else weird got home and was listening to the radio (now that I have a new battery I can do that now on short trips) but I wanted to finish listening to the song so I turned the key back one position to keep the radio on and all my gauges turned off but the car stayed running.. Bad ignition switch?
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