Charge indicator

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Ontspaners

New Member
Joined
Oct 15, 2018
Messages
2
Location
Great Harwood
Car
Ml270
Help please after suffering from flat battery, changed batter for brand new, changed altanator twice, still getting flat battery! Did not notice charge light or battery symbol was not illuminated, put volt meter in cigar lighter socket to monitor voltage, at tick over or revs below 1100 I'm showing 11.7 volts with lights etc on, swapped bulb in charge indicator and its working but not illuminating either at ignition switch on or with engine running, once revs get over 1200 it's showing 14.2 volts, can anyone point me to the solution please
 
Had something similar on my 1997 R170. Issue proved to be a break in the low current connection at the alternator. It looked good but was in fact open circuit. This stopped the charge light working and also as no 12v feed into the alternator the alternator had no output.

You maybe lucky and have something similar. Hope so as a free fix.

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Had something similar on my 1997 R170. Issue proved to be a break in the low current connection at the alternator. It looked good but was in fact open circuit. This stopped the charge light working and also as no 12v feed into the alternator the alternator had no output.

You maybe lucky and have something similar. Hope so as a free fix.

Sent from my SM-T710 using Tapatalk
Many thanks, I was told this by my indi but not sure where the wire comes from, we think it's at the fuse box but unsure, thank you
 
Also worth checking there's no current drain elsewhere..

Take out as many fuses as you can and see if there's a difference at tickover. Then progressively put the fuses back until the problem reveals itself.
 
May be like so many mercs. And if the bulb in the dash is never lit it will need replacing .The bulb joins up the circuit if is blown it wont incite the alternator
 
Many thanks, I was told this by my indi but not sure where the wire comes from, we think it's at the fuse box but unsure, thank you
My 170 is exactly as Optimusprime says above. The wire actually comes from the "ground" side of the indicator bulb and provides the initial excitation voltage. Once the alternator spins up it provides voltage at this connection rather than a 0v "ground" and hence the bulb goes out. If it were me I would be checking carefully around the alternator first as that lives in a harsher environment than the rest of the circuit. First I would now check I have some volts at this alternator terminal with ignition on but engine not running. If nothing I would rig a temporary 12v feed from the battery via a 12v bulb and check the alernator then generates power and after that it's then hunt the break in connectivity which I guess worst case could be in the intrument cluster itself.

I have to own up that in fact I didn't do the above but stupidly jumped the gun and bought a scondhand instrument cluster from ebay which of course was a complete waste of time and money!



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