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  #1  
Old 10-24-2011, 06:23 AM
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'95 E300 gauge problems

Guys,

After searching and browsing 14 pages of posts on "gauges" I have a couple questions:

I'm helping out with the wiring on a '95 E300. After getting the engine wiring replaced and working well, the oil pressure and temp gauges don't work. I don't have a wiring diagram so we have to visually trace everything with is a huge PITA.

So, which actual sensor is for the gauge? There are 3: one in front and two in the back of the engine.

How does the gauge panel come out?

Is there a "typical" problem with these gauges that I might look at as a start?

Thanks for the help!
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  #2  
Old 10-24-2011, 10:57 AM
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Ive seen the same problem on this forum earlier, apparently the oil pressure sensor can suddenly die. but if it helps;

The sensor for temp gauge is the 2 pin one closest to the firewall, it is two sensors built into one, one output is for the glow relay and one output is for the temp gauge. The 4 wire round one is for the ELR and EGR, and the front blue one is for the Climate control unit.

The oil pressure is in its obvious place though - below the oil filter housing.
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1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)
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Old 10-24-2011, 12:15 PM
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OK, that's interesting since the rearmost sensor is only a 2 wire unless I'm missing something. I see the round one with 4 leads immediately in front of the rear sensor.

What would be really helpful is a pin out of the 14 pin connector on the firewall.
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  #4  
Old 10-24-2011, 12:44 PM
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Yes - that rearmost 2 wire sensor is the one for the temp gauge and the glow timer too. Each pin is a separate sensor.

Pin 1 (read on connector) green wire is the lead to the coolant gauge, pin 2 white wire is the lead to the glow relay. The wiring connectors to these are under the fuse box panel, both 4 and 12 pole ones.
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1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)
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Old 10-24-2011, 01:21 PM
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OK, got it. They vary the connection to ground rather than to one another. That helps a lot, thanks. Now, how do I get this instrument panel off!
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Old 10-24-2011, 01:24 PM
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the instrument panel is a push fit, get two wire hangers and make some L shapes from them about 6 inches long, make one edge into a small hook. insert the tools at about 2 inches from the bottom of the cluster at either side, engage the hooks by turning them towards the cluster and pulling it out, You might want to unhook the speedo cable from its little holding bracket near the brake pedal - you will need to remove the top mat and the foam carpet mat, otherwise the cluster will not pull out enough to remove the speedo cable.
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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)
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Old 10-26-2011, 06:52 AM
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Thanks for all the info! We had success with the temp gauge last night!

Now, it's on to the oil pressure gauge. It's pegged at "3" at all times the key is on. After removing the key, it sticks at the top but will drop after a gentle pounding on the top of the dash.

It does this with the sensor connected or not so I suspect it's in the dash somewhere. Also, another question about the sensor:

When I measure impedance to ground, there is never any reading - car running or not. Should there not be a sliding scale based on the oil pressure at any given moment?

I even tested impedance to the sensor housing to ensure a good ground.

Thanks for the thoughts.
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  #8  
Old 10-26-2011, 10:44 AM
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If your gauge is pegged at 3 with key on engine off, the wire from the sensor is open circuit.

test the wire from the sensor to the cluster and for testing purposes get a 100 ohm resistor from radioshack and put it on the sensor wire and route to ground - the gauge should be between 1 and 2 on the scale. If it shows correctly the sensor is bad.

When its correctly functioning and in TX weather running 15W40 Delo lube, I have 3 bar at cold startup on idle speed and 1.5 or 1.6 at idle speed when temp gauge is showing 80-90 celcius. Immediately going to 3 when the engine is revved to 1200 rpm (drive)
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1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)
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Old 10-26-2011, 11:59 AM
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So, the sensor shows a dead short to ground when the pressure is low? Hence the high reading with an open circuit?

My test on the sensor last night showed an open circuit with the engine running or not which would indicate to me that the sensor is bad.

However, the gauge will not read at all regardless of any connection to the wire, ground or open. This would tend to indicate to me a break in the circuit somewhere.
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  #10  
Old 10-26-2011, 01:05 PM
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yes - you are correct. - Trace the wire continuity to the cluster. Maybe it suffered "biodegradation' which plagues the later W124 wiring
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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)
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  #11  
Old 10-26-2011, 05:35 PM
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Cool, thanks. We've already re-wired the entire engine wiring harness which was completely shorted out. It was missing all of the insulation.
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