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Discussion Starter #1
I am in process of installing an air-fuel gauge.

Need to run the cable from an O2 sensor located somewhere on the exhaust (exact spot not chosen yet) up into the dash - somewhere.

Issues:

- Wiring from sensor has upper temperature limit of 105C. Need to keep it away from exhaust pipes. Need to find best route.

- limited options for gauge installation - Maybe replace ashtray with panel. Or put it in clock location (where I now have fuel pressure gauge). Or mount a bracket or pod somewhere.

- Find an opening in firewall or above transmission where I can feed through a connector that is 5/8" x 1/4" and get at so as to pull it into interior of car.

Anyone run any similar wiring, installed additional instruments or have any ideas?
 

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Heres how I did my custom O2 sensor installation.

The white channel I used to bring the rear sensor O2 and wheel speed wires to the back of the car was from the electrical department in Home Depot.

The attached photos are using the sensors and wire harness parts from a 1996 SL600. The wire harness terminates at 4 pass through convectors and the O2 sensors connect from the underside. If you find just about any year 129 (later years have the rear sensors) in a junk yard you can lift the carpets and pull these pass throughs out along with a section of wiring you can splice. Also take the O2 sensors as they will have the proper mating connectors to splice to your systems O2 sensor.

I'm assuming you are fitting one O2 sensor on an early 107. I believe you have 2 parallel pipes going to a 2 in to 2 out muffler. Best solution would be to fit an X pipe before the muffler and put the O2 sensor bung right between the back crotch of the X.
 

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Premium Member
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Discussion Starter #3
Heres how I did my custom O2 sensor installation.

The white channel I used to bring the rear sensor O2 and wheel speed wires to the back of the car was from the electrical department in Home Depot.

The attached photos are using the sensors and wire harness parts from a 1996 SL600. The wire harness terminates at 4 pass through convectors and the O2 sensors connect from the underside. If you find just about any year 129 (later years have the rear sensors) in a junk yard you can lift the carpets and pull these pass throughs out along with a section of wiring you can splice. Also take the O2 sensors as they will have the proper mating connectors to splice to your systems O2 sensor.

I'm assuming you are fitting one O2 sensor on an early 107. I believe you have 2 parallel pipes going to a 2 in to 2 out muffler. Best solution would be to fit an X pipe before the muffler and put the O2 sensor bung right between the back crotch of the X.
Unfortunately where we are up here, our junkyards have NO Mercedes of any kind! I checked all of them last week looking for some other parts.

The X-pipe would be a good choice, but probably more than I want to do. Installing bung in H-pipe crossover was one thought, but gas there is probably not well mixed. May install two bungs with ability to switch locations, but depends on how much slack I have in connecting wire.

I see you have an opening on tunnel on passenger side. I found a pic on oughtsix's site and that is where he brought sensor wire through. I like the idea of bringing the wiring inside car as quickly as possible.

Thanks for the input!

Graham

The unit I bought has all teh connectors and cables, so I just need to
 

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Unfortunately where we are up here, our junkyards have NO Mercedes of any kind! I checked all of them last week looking for some other parts.

The X-pipe would be a good choice, but probably more than I want to do. Installing bung in H-pipe crossover was one thought, but gas there is probably not well mixed. May install two bungs with ability to switch locations, but depends on how much slack I have in connecting wire.

I see you have an opening on tunnel on passenger side. I found a pic on oughtsix's site and that is where he brought sensor wire through. I like the idea of bringing the wiring inside car as quickly as possible.

Thanks for the input!

Graham

The unit I bought has all teh connectors and cables, so I just need to
All the O2 holes I have were drilled by me. I also used nutserts and stainless cap screws to hold them in place. You might be able to go on Ebay and find just about any MB parts car will have these pass throughs. I wouldn't use the H pipe, too stagnant. Duel sensors would be better. Some clever electronic wizard might be able to come up with an averaging circuit that you could use along with a 23 position switch for left right and average output. great for troubleshooting.
 

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Discussion Starter #5 (Edited)
All the O2 holes I have were drilled by me. I also used nutserts and stainless cap screws to hold them in place. You might be able to go on Ebay and find just about any MB parts car will have these pass throughs. I wouldn't use the H pipe, too stagnant. Duel sensors would be better. Some clever electronic wizard might be able to come up with an averaging circuit that you could use along with a 23 position switch for left right and average output. great for troubleshooting.
I am a bit too impatient to get this done to wait to order stuff of eBay ;)

I had a look under the car - It looks like one of the locations marked in pic below should work (Car is not currently like this!)

Option 1 - seat rail is a bit in way - might be able to get through in front of it and put in a large enough grommet so as to allow o2 sensor to pass thru and keep connector & resistor inside car.

Option 2 - drill new hole or somehow use gear shift boot to feed wire thru. Connector and resistor would be under car.

Option 3. Noticed a rubber grommet sticking down - must be under dash somewhere - nothing passing through it. Maybe it is A/C drain? It is directly above the kickdown solenoid. Anyone know where that is on top side?

The grommet that the solenoid wire passes through is another option - But have to find that on top side too.

I kind of like Option 2 because it is close to the ashtray which is most likely spot for gauges. But others would get me close to there too.

All suggestions welcomed - we had visitors so work closed down for the day :(

At least I now know where to weld bungs - probably one on each of the bends just before the muffler, just below the opening that gets me to Options 1 & 2. And not far if Option 3 turns out best.
 

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