OHMS is the next section of the meter counter-clockwise from the DC volts. It has a greek omega symbol, looks like an O that is opened up at the bottom with two feet sticking out.

You want to use this setting to see if the battery cables etc are well connected to their termination points. So, use a fairly low range and check from neg post to the body (frame) bare metal somewhere close by. Also check the engine to body in same way. You want a fairly low number, but likely won't be zero.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

Turn the dial to the setting I said is for other stuff and you should see a #1 on the screen; touch the 2 bare metal probes on your meter wires togeather and hold the firmly togeather. Watch what happens. The 1 should go down to 000 (it dose on mine) or 001 something very low. This tells me that the wires are making a complete circuit with little or no resistance. A good wire on your car should have little or no resistance. If you touch one probe to 1 end of a wire and the other to the opposite end and you still see the 1 on the screen it means that that wire is broken or burned inside (an open circuit) and no electricty is being conducted through the wire. Now try it on a 100 watt light bulb (on the table). put one probe on the threaded part of the light bulb and one probe in the center of the bulb. On my light bulb I got a 10. This tells me that the bulb has resistance and that the circuit is good.

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84 300D, 82 Volvo 244Gl Diesel

Well its raining hard but as soon as the dogs get up ill take em out and check the connections. Thanks for the advice

Used a jumper cable to check thr ground and still nothing, No lights-No Power. What should i start checking? Should i try a different battery?

I have been following this story and tried to help but without being there I am all out of answers. I hope someone local will step up and help.

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84 300D, 82 Volvo 244Gl Diesel

Not sure how much testing you have done but I would do the following:
Set meter on voltage. Put one lead from the meter on the engine or chassis and the other to the positive pole on the battery. If I got 12 volts there, I'd trace out the positive wires from the battery, checking to see how far down thru the wiring I can read voltage.
One easy place to check is the strip fuse in the glowplug relay. There should be 12 volts at it.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The only testing I've done since its raining is putting a jumper cable on the negative and attaching it to the frame and no go. So from what i understand that means that its not a bad grounding strap?

Diesel911 don't give up on me yet. I just have never had to find a faulty connection before and don't know how to start. Do i go to the fuse box and start checking? What do I check when im checking wires coming from the battery? Connect a probe to the positive post and then at the other end if i get anything other than 000 or similar than ive found the problem.

From what im understanding, if the battery has 12+v, then next would be the starter cable, then the small wires coming from the starter to the junction box, what else

thanks so much for all of the help, Ive never struggled so much with mechanical things, On my old 4x4 Chevy it was a cinch to work on and my dad helped with anything electrical, i know how to replace and unbolt and bolt, just slow on the diagnoses so thanks again for your help and advice.


ps is there a way to search the members of the forum by state?

Okay I'm having some trouble with the electrical system on my 1984 300D. Im not getting any electricity (no lights, no crank, nothing) I replaced my starter cable with a jerry rigged cable ( 2ga battery wire, and then 2 10ga wires to the junction box, one with a larger ring terminal) just like the original.

My question is do both of the ring terminals connect at the same place on the starter solenoid?

The whole manual:
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/Index/617Tindex.html

Wiring diagrams:
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/ETM/81_300_2.pdf

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84 300D, 82 Volvo 244Gl Diesel

Batteries can have 12V, but not be able to supply enough current to run anything. You said it is a new battery, so it is unlikely this is the case. If you want to test it, connect your multimeter across the battery, then turn the headlights on. The voltage shouldn't drop by more than a volt.

Given your problems, and what you've already checked, this might be worth verifying.

After that, start following the voltage with your multimeter. Is there 12V across the + terminal of the battery and the chassis of the car? Then start following and checking the + cable and everything it connects to. Chances are, you'll some disconnected or broken off wire along the way.

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

the headlights aren't getting power either. Do these have "fusable link"

Listen. Do what Kerry suggested. Take your meter, set it to DC volts and check between the battery positive and something metal in the engine bay, such as a clean, non-rusty bolt head.

Try a number of places such as that and report back.

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1998 E300 +310,000K
1996 E300 +460,000K

Know what, before you do that, make sure that both battery connections are so tight that you can't twist them with your hands with all your might.

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1998 E300 +310,000K
1996 E300 +460,000K

Your car is probably identical to mine.. here's the relevant electrical diagrams from mine:


Battery to headlight switch



Headlight switch to headlights.

Yes, there are four fuses, on each for low/hi, left/right. My guess is that the wire came disconnected at that first juncture, if not that, then at the second.

Of course, maybe your wiring is more like what my manual says started with 1985:



Which has the battery connect directly to the starter. You said you replaced the starter.. didn't leave a wire off it or anything, did you?

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

okay all the wires are reading good,

cant seem to locate the fuses that patbob is talking about, where do i look for these at