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95 E320
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8 Posts
Discussion Starter #1
Hello,

I’m hoping someone here could point me in the right direction with a problem on my 95 e320.

background—
I picked up a relatively clean 95 e320 a few months ago to use as a daily driver. I’ve previously owned a 91 190e while living in Germany, and was super excited to get back into Mercedes cars after spending time in the audi universe. The car needed a lot of updating a few weeks into owning it—all the vac lines were cracked, headlight adjustment tabs were broke, interior water leaks, valve cover gaskets, fluids, etc. The car is from FL, so luckily no frame rust, except some cosmetic surface rust around the usual spots.

The problem I’m having now is the turn signals/horn. After a few weeks of driving the car, the turn signals, and outside temperature display would intermittently stop working. I could remedy this by pressing the horn, and the electrical gremlin would return the turn signals to working order. A few weeks passed, and now the turn signals and horn are both inoperable, with the temp display turning off while either input is toggled (pressing the horn, etc).
So far, I’ve bypassed the alarm, cleaned the number 6 fuse contacts, removed the k38 relay and cleaned internal contacts, checked wiring for degredation—none of which have helped thus far.

Is there a hidden relay for the horn/signals/temp display that I’m missing? Am I correct in assuming the hazard relay is independently wired to the turn signals—outside of the turn signal stalk wiring?
I’ll try to post a video showing the above issue, if I can figure out how.

Thanks in advance!
 

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80 280SL, 85 300SD, 87 300TD, 90 300TE 4Matic, 90 300D 2.5 Turbo, 92 300D 2.5 Turbo, 92 300TE 4Mat
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1,462 Posts
Does the car have an updated wiring harness? Perhaps there is a loose connection in the fuse box at the underside of fuse 6, such as the screws that hold the wires to the contacts.
 

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Premium Member
2003 G500, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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1,045 Posts
Fuse 6 is the common denominator among all the items that are non-op for you. If you have a voltmeter, check for +12 on both sides of Fuse 6 with the key on and the horn pressed on the steering wheel (this will be a two person job). If it's there, check for +12 on pin 3 of the K38 relay with the key on. If it is not there, there could be an issue with the connections in the fuse box itself.
 

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95 E320
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8 Posts
Discussion Starter #5
The car unfortunately has the factory harness—which is my next repair. I’m taking the fuse box apart now to check connections, and hopefully will discover the issue.

Side question: I’m taking apart the steering column to diagnose a non-functioning telescoping adjustment motor, and found a silver electrical box mounted to the left of the steering column, labelled CARB 0155454332(01). The connections on the back side of this control unit are terribly corroded. Any chance someone knows what this box is?
2613231
2613232
2613233
 

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95 E320
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8 Posts
Discussion Starter #6
Checked the connection under the fuse block @ #6 and it’s tight—no corrosion either. I’m starting to suspect my k38 is bad, or that my non-functioning alarm is somehow causing the issue.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,074 Posts
There is green death on the back of that MAS module. Considering it is located underneath the dash, a main possible cause is a leaky windshield due to a botched replacement by one of the mobile glass guys.

Start by removing the green death using deoxit or similar spray.

Also ditch all the fuses and replace them with a full set of copper core ceramic fuses made by Flosser.
 

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Premium Member
2003 G500, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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1,045 Posts
You must have a California car because I'm pretty sure that the module in your picture is the CA only emissions diagnostics module. Definitely clean the oxidation off, but I don't think it is the cause of your problems. From your video, it seems pretty clear that there is a high resistance connection somewhere in your Fuse 6 circuit that is causing a loss of voltage when a significant load is applied. The temperature display module draws very little current and so stays on until a more substantial load like the turn indicators is placed on the circuit. As I said before. measure the voltage on Fuse 6 with and without a load.
 

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1993 300CE Cabriolet (mine) ; 1994 E320 Wagon (wife's) ; 1990 Benz 300E 2.6 (son's)
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6,985 Posts
indeed, thats module N59 on this page of the wiring diagrams.

its connected to the rather limited CANbus on these cars to get diag codes from other control modules, the check engine light on the dashboard, and the blink code light on the diag connector near the battery on california cars.

the black knob on top is turned to unlock it so you can unplug it from the big jack assembly its plugged into...
 

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95 E320
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8 Posts
Discussion Starter #10
You guys are awesome. The corroded N59 module correlated to the non-functioning diagnostic light issue I’ve been having.

With the turn signal/horn/temp display issue, I isolated the horn/turn signal wiring harness under the steering column, turned on the signal indicator via stalk, and wiggled individual wires until the indicator turned on. Guess I’m going to be taking apart the airbag/wheel this week to figure out which wire or connection needs to be fixed.

I’m used to electrical gremlins having worked for several years as a utility helicopter crew chief on 1970s/80s aircraft, but this car is something special.

I’ve also just failed emissions here in CT, and inturn replaced nearly every emissions component possible except for the egr and vac crossover. I guess Mercedes will continue surprising me well into the remaining years of ownership.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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Failing emissions might be as simply as needing to rotoroot the EGR tube. The EGR valve hardly ever fails on a MB, unlike Detroit junk. IF it is failing due to excessive HCs, then it is almost guaranteed to be the MAF sensor.

Also be aware that the O2 sensor is a wear and tear item. If it's more than 10 years old or has more than 100K on the clock, it's as done as a Thanksgiving turkey. Replace with a new Bosch sensor as needed. Amazon has the best prices on Bosch O2 and MAF sensors.
 

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95 E320
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Discussion Starter #12
I replaced both the MAF and the 02 sensor since failing the emissions test with new parts. And all of the old brittle vacuum lines/rubber boot connectors. I also did plugs, coils and boots. I am getting an odd surge when I press the throttle under 3k rpms—a feeling I can best describe as turbo lag. And my exhaust reeks of fuel, with a noticeable consumption via fuel gauge (1/8 tank in 15 miles of stop and go traffic).

Could just be the wiring harness needing to be replaced, however.
By the way, which date on the harness label states the manufacture date? As I was looking on eBay, some sellers listed the number after F.D. And some used another date on the opposite side. Pictures with the highlighted dates included below.
2613442
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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The F.D. is the manufacture date, so you are good on the harness BUT what about the throttle body? It suffers the same eco junk disease. Unstable idle and surging are telltale signs that the throttle body is at fault.
 

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2003 G500, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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1,045 Posts
As sbaert said, surging and that turbo lag feeling are the telltale signs of a failing throttle body. Check the date code on the label of your TBA to see if it falls in the ecoo junk category.

But the throttle body is not likely to be the cause of your high fuel consumption and/or gas smell in the exhaust. I would investigate the fuel injection temperature sensor because if it has failed to a high resistance (an open or shorted temp sensor will throw a fault code), the engine will think that it is "cold" thus causing the engine to run enriched all the time.

Have you read the flash fault codes from the diagnostic connector (I assume you have, but just checking)?
 

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W124
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Drift away. As long as there is good information is in here, a search engine will find it. The days of searching for thread titles is long gone.
 
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