83 300sd Brake Lights Blown Fuse help please - Page 3 - PeachParts Mercedes-Benz Forum

JamesDean · #1 03-15-2012, 10:34 PM

Quote:

Originally Posted by ShadeTree300SD

JamesDean, I see a meter on HF website just like the one you had a picture of for $3.00! That seems to good to be true but I'll go fetch one up in the morning. I'm from Idaho so maybe I could get you to go reeall slooow and explain how to set up the meter on the fuse. I guess the car would be running?

Certainly, its very simple.

Set the meter to 10A (about 5-o'clock)

Connect the probes appropriately (black to COM, red to 10A).

Put one lead (doesnt matter which) on the top copper spring clip where the fuse would sit, and the other where the bottom of the fuse would sit.

You are simply replacing the fuse with the meter. For the purpose of this experiment you don't want to let them sit too long, as the meter is unfused, just long enough to get a reading. A few seconds, the number should steady out to something.

I'll check my SD shortly and post a picture for reference.

JamesDean · #2 03-15-2012, 10:50 PM

Hm the warning relay is interesting. When mine was ON, I had a .750 A draw on the circuit, other wise the circuit only drew what the picture shows:

Hope this helps when you go to test yours.

Those large black relays you see aren't factory, I added them in for the keyless entry system, don't mind them.

Yak · #3 03-15-2012, 11:40 PM

I assume the meter also has specific settings for current with the lead positions - if so, make sure the wires are plugged into the correct places.

Measuring volts, or ohms, you might need to move the wires.

A tiny bit of meter theory:

Measuring volts, the electricity doesn't flow through the meter - it's an open circuit.
Measuring amps, it does flow through, so it's a short circuit.
Measuring ohms, it needs a little power to measure the voltage drop, so it ADDS current.

As long as you know what you're trying to measure, you can just read the face of the meter to set it up. Sometimes it's useful to get a sanity check by measuring a known quantity; e.g. "am I using this right? Is it measuring correctly, or at least what I'm looking for?"

TnBob · #4 03-16-2012, 02:47 AM

That $3 meter is the correct one. It will eventually need a new 9V battery if you do much resistance checking.

At $3 consider getting 2 meters ~!~

ShadeTree300SD · #5 03-16-2012, 01:08 PM

Ok, got the meter. I set it on 10a, removed #12 fuse and tested. Here are the numbers:

Key on engine off = .64
Engine running = .62
Engine running brakes on = 4.01 max
Engine running, brake on, left turn signal on = 6.50 max
Engine running, brake on, right turn signal on = 6.89 max

I went under the car and found the single wire going to the back of the tranny and at first I thought it was rubbed raw on the crossmember but I don't think it is. What happens if this is disconnected?

Do I need to remove the center console stuff to get that carpet off the side of it? I took the floor carpet out but was afraid to yank to hard on that side carpet.

I disconnected a plug that was to the left of the cruise control amplifier, is that the warning thingy?

Thanks to all for the guidance and help!

ShadeTree300SD · #6 03-16-2012, 01:10 PM

Thank you Yak for the Meter Theory info! That's helps and it will be really great for me to get a better understanding of this stuff!

JamesDean · #7 03-16-2012, 01:15 PM

Quote:

Originally Posted by ShadeTree300SD

Ok, got the meter. I set it on 10a, removed #12 fuse and tested. Here are the numbers:

Key on engine off = .64
Engine running = .62
Engine running brakes on = 4.01 max
Engine running, brake on, left turn signal on = 6.50 max
Engine running, brake on, right turn signal on = 6.89 max

These numbers all sound acceptable. Each tail light / turning light is about 1.5 A draw each.

Quote:

Originally Posted by ShadeTree300SD

I went under the car and found the single wire going to the back of the tranny and at first I thought it was rubbed raw on the crossmember but I don't think it is. What happens if this is disconnected?

That is probably the speedometer sensor wire.

Quote:

Originally Posted by ShadeTree300SD

Do I need to remove the center console stuff to get that carpet off the side of it? I took the floor carpet out but was afraid to yank to hard on that side carpet.

The center console carpet is held in by a screw in the vicinity of the gas pedal. If you've removed the knee panel, remove the screw and the carpeting should be able to be removed.

Quote:

Originally Posted by ShadeTree300SD

I disconnected a plug that was to the left of the cruise control amplifier, is that the warning thingy?

It should have been to the right of the cruise control unit, they share a bracket.

ShadeTree300SD · #8 03-16-2012, 01:45 PM

On the far right side under the glove box there is only one box on that bracket. Maybe I should get a photo.

Ok, removed the the carpet on the drivers side of the console. There is an odd looking coiled white wire in a deteriorated sheath that goes out the side of the tunnel near the tranny. I saw it while underneath also and it doesn't go to anything. Small gauge white wire, very strange looking.

JamesDean · #9 03-16-2012, 01:48 PM

Quote:

Originally Posted by ShadeTree300SD

On the far right side under the glove box there is only one box on that bracket. Maybe I should get a photo.

Ok, removed the the carpet on the drivers side of the console. There is an odd looking coiled white wire in a deteriorated sheath that goes out the side of the tunnel near the tranny. I saw it while underneath also and it doesn't go to anything. Small gauge white wire, very strange looking.

The cruise control amplifier is located under the driver's side dashboard. Just left of the brake pedal. The warning box is like 2-3 inches to the right of it.

Thats the evaporator drain tube. If its deteriorating, you should consider replacing it. Water flows down through there and if you find a puddle on your floor in the car, you'll know why. I'm not sure why they used that type of hose. Weird stuff.

JamesDean · #10 03-16-2012, 03:18 PM

Try that plug at the right of the gas pedal, look at it see if anything looks amiss.

JamesDean · #11 03-16-2012, 03:22 PM

That might be something indeed! That second one was the one I'm was talking about previously.

If your evaporator drain hose is leaking water into the cabin then it very well could have gotten that connector wet. Disassemble it and clean it up. You might have very well found the problem.

It is possible. I believe you can pry it out with a screw driver, or perhaps move it in one direction or another and it will unclip. I cannot remember.

ShadeTree300SD · #12 03-16-2012, 04:41 PM

Ok, I took the connector closest to the gas pedal apart and cleaned it all up and reassembled it. I popped yet another fuse in the socket and drove off with my fingers crossed! At roughly the same place (speed & distance) I applied the brake and 1 or 2 seconds and pop goes the fuse. I thought, what the cuss!! So, I go back and I decide to unplug the other connection (the one that's about 4-5 inches away towards the rear of the car). I put in yet another fuse and head out. I tried everything and could not get the fuse to blow!! So, is this a victory of some sort? What is this connector for and where do the wires go?? Anyhow, my fingers are still crossed!!

JamesDean · #13 03-16-2012, 04:49 PM

Can you take a picture of this connector, I'm not picturing its location for some reason.

Yak · #14 03-16-2012, 05:18 PM

Quote:

Originally Posted by JamesDean

Can you take a picture of this connector, I'm not picturing its location for some reason.

A pic w/ a brief description of wire colors, since they don't always come through. Quantity of pins, would help too.

ShadeTree300SD · #15 03-16-2012, 05:51 PM

Here's a photo of the connector. The connector with the brown gooey stuff is the one on the left with the purple wires. The one we are talking about now is the one that is unplugged on the right side if the air duct and center of photo.

It is a 8 pin connector wires are as follows:

Top row from left to right - Blank, Red, Red w/white stripe, Brown
Bottom row from left to right - Gray w/purple stripe, Brown, Red w/black stripe, Red w/yellow stripe