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  #1  
Old 09-13-2016, 12:20 PM
szamik's Avatar
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Thumbs down m104 3.0 Drain battery. Problem with OVP relay

Hi

I need some of advice because i have quite a big problem with my w124 3.0 with KE-Jetronic and i don't have any idea how to resolve it .

Battery after one night is completly dead. I measured power consumption by connecting in series multimeter. Consumption was about 0.01 amps so i was quite suprised because thats good result. After a while I found something strange. When I started the engine, then I stoped it and turn off ignition I still have power on whole kejetronic... Idle speed valve, air flow potentiometer and also diagnostic socket (between pins 3 and 5 there is 12,5V). So I looked at OVP relay, and Voila. When i took off fuses from that relay, coils and ABS pump made "click" and power was gone I looked into diagram on OVP relay. Pin number 30 this is constant plus, 31 a ground and at the pin 15 power is only when the key is on. So I thought that something is wrong with ignition and pin 15 still have power even when key is on. But unfortunately no Even if I pull of the key and close the car, pin 15 does not have power. I don't understand how it is possible that coils are still egaged even if pin 15 does not have +12V. I changed OVP for new one but still the same.

Could you give me some advise? :-)

Thanks a lot.

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  #2  
Old 09-13-2016, 02:05 PM
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s:

Consider the possibility of a shorted diode in the alternator, either in the main charging rectifier, or in the secondary, energizing circuit.
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Old 09-13-2016, 02:35 PM
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Quote:
Originally Posted by Frank Reiner View Post
Consider the possibility of a shorted diode in the alternator
Battery is charging correctly (13.8V) so I may think that alternator is in good shape, but tomorrow I am going to check diodes.

Quote:
Originally Posted by Frank Reiner View Post
or in the secondary, energizing circuit.
Whats that mean ?



There is one thing which I forget about. I don't know whether this may be connected with main problem, but ASD doesn't work at all. ASD light is flashing all the time and orange triangular on dash only flash one times when I turn key on. I wanted to check blinking faults in 16 pin diagnostic socket but pin 5 is shorted to the ground... So when i connect "flashing device" into this pin, LED flash all time. I thought that ASD unit is broken/shorted or something but when I pull of it, main problem didn't resolve.

Last edited by szamik; 09-13-2016 at 02:48 PM.
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Old 09-13-2016, 03:04 PM
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Trevor Hadlington
 
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Is you car electrics the same as the W124? You have this charging light in the dash, if the bulb is not alight after you turn your ingnition on, then the bullb is shot and its the inciter for the alternator citcuit So no light, no charge to battery . Regulator can give a number of problems .See Kent Bragsna on youtube..
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Old 09-13-2016, 04:14 PM
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Originally Posted by szamik View Post
Battery is charging correctly (13.8V) so I may think that alternator is in good shape, but tomorrow I am going to check diodes.



Whats that mean ?
13.8V is a bit low; 14.2-14.5V when a good battery is at full charge.

There are six diodes in the main rectifier, and another three diodes in the initial energizing circuit for the field.
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Old 09-13-2016, 08:25 PM
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13.8 is perfectly normal. Regulators for this era were typically limited to 14V. That number could go lower depending on temperature, load, and state of battery charge.

I don't think this is a shorted diode. Maybe an ignition switch problem.
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  #7  
Old 09-14-2016, 02:55 AM
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Originally Posted by Mxfrank View Post
13.8 is perfectly normal. Regulators for this era were typically limited to 14V. That number could go lower depending on temperature, load, and state of battery charge.

I don't think this is a shorted diode. Maybe an ignition switch problem.
I also thing that 13,8V is not bad result.


Quote:
Originally Posted by Mxfrank View Post
I don't think this is a shorted diode. Maybe an ignition switch problem.
I don't think so because I if not run the engine, only turn key to ignition and then turn off it, coils in relay are open and then close properly. There is something wrong just when the engine is running (so problem with alternator is quite logical). I just can not understand how it is possible that coils in OVP are shorted when on pin 15 there isn't any voltage



I made another simple test. I disconnected both cables of alternator, then I starded the engine. Problem didn't resolve so I am almost sure that alternator is not a reason in this case

Last edited by szamik; 09-14-2016 at 04:38 AM.
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Old 09-14-2016, 05:26 AM
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Sorry for double post but few minutes ago I replaced voltage regulator and unfortunetly it didn't resolve the problem.

Bulb of battery is on when I turn the ignition on and after I start the engine it goes off so I think there is everything okey with alternator and battery (yes, I replaced it too)
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  #9  
Old 09-14-2016, 03:32 PM
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The antenna's on cars from this era are notorious for draining the battery. Pull the fuse for that circuit and see if it helps or if you like - measure current across it with fuse out.

Do a search on this. Numerous discussions.
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  #10  
Old 09-14-2016, 04:35 PM
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Have you read my first post?

There is only problem with OVP relay and fuses inside it.

I firstly checked all fuses in fuse box of course but there is everything alright Unfortunetly...
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  #11  
Old 09-15-2016, 08:55 AM
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Trevor Hadlington
 
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SZAMIK Can you google this Mercedes Benz Model 124-m104 Maintenance Manual Its all in there how to check it ,but searching is time taking. let me if its of any use to you .

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