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1992 190E sportline, 1993 300ce, 1993 300ce sportline, 1992 300sl
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115 Posts
Discussion Starter #1
Just noticed after some work at my indie that my mpg gauge is swinging across the dial up and down, and very slow to return to 0 - used to be very controlled and was always the same. What and where is the trigger for this from the EZL? I have also noticed that the shift point from 4th to 5th ( this is a 1992 300sl with an auto with electric 5th gear) is about 5 mph higher than it used to be. seems to be an electrical issue, possibly an ovp going bad?
 

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Premium Member
2002 Black SL500, 1998 Red sport SL500, 2005 Silver (A209) CLK500
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1,010 Posts
Runs off of vacuum I believe. If the shop was doing repairs under the hood or under the dash....perhaps....a plastic fitting came undone, loose, cracked...
 

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Premium Member
2002 Black SL500, 1998 Red sport SL500, 2005 Silver (A209) CLK500
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1,010 Posts
It is electric, no vac connection to gauge.
That is why I said...I believe...and obviously incorrect. Still...shop could have brushed against a wire and loosened it....shorted out...
 

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1997 SL500 Sport pano and 2010 R350 4Matic
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323 Posts
MPG gauge moves when i apply the breaks


Sent from my iPhone using Tapatalk
 

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Registered
1992 190E sportline, 1993 300ce, 1993 300ce sportline, 1992 300sl
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115 Posts
Discussion Starter #6
I will have to go back to the shop that worked on the car and ask them to look at it and see if it was something they affected while working on other issues.
 

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1999 ML320, 1998 SL500
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859 Posts
MPG gauge moves when i apply the breaks


Sent from my iPhone using Tapatalk
Wow, I don't get anything close to 30 MPG when cruising at 250 MPH.
 

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Outstanding Contributor
R129 500 SL 1991
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1,044 Posts
... What and where is the trigger for this from the EZL?...
The N3 KE injection controller provides a fuel consumption voltage signal to the microprocessor on the instrument cluster pcb that controls the mpg gauge. The microprocessor also receives the speed signal from the left front wheel sensor via the ABS. Given these two inputs the microprocessor on the cluster pub calculates the mpg consumption and sends the appropriate signal to the MPG gauge.

If the electrical connections at the rear of the cluster or N3 controller are corroded/bad, or the N3 or OVP is bad, the MPG gauge could swing wildly to the right to MIN mpg when the engine is started, and then to the left to MAX mpg when the car starts rolling > 15km/h. There would be no finesse betweend MAX and MIN that you would normally see.

When a gauge starts to go wrong, there are usually no obvious warning signs, and when it goes it just suddenly stops working.

Of all the ancillary gauges the mpg gauge gets used the most, and is subject to the most wear and tear. The first thing to go is the mechanical compliance in the gauge. If you physically move the mpg needle it should return slowly to its rest position. If it swings back quickly, this is a sign that the gauge is worn.

If your MPG gauge is completely dead so that the needle does not move at all, the cause of this would be unclear because it could just be a faulty gauge, and/or there could be underlying issues with the wiring/connectors, OVP or N3 controller.

The effect of defective cluster capacitors on the mpg gauge is also uncertain. Maybe others could comment.
 

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1992 190E sportline, 1993 300ce, 1993 300ce sportline, 1992 300sl
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115 Posts
Discussion Starter #9
will replace the ovp and will see if that fixes the guage
 

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Registered
1992 190E sportline, 1993 300ce, 1993 300ce sportline, 1992 300sl
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115 Posts
Discussion Starter #11
I have replaced the ovp with a new mb part and it still does not act as it normally does. Seems to be working somewhat better but still swings and returns to 0 - right side of gauge slower that it used to and not as 'accurate' as it was. It no longer stays in the max setting - indicates @ 30 mpg when cruising but we all know that is a fantasy.
 
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