both blinkers at once - PeachParts Mercedes-Benz Forum

ImBroke · #1 11-22-2009, 04:25 PM

This is funny. Well, not really, but it sort of is. Hazards work fine. Turn on either blinker, and they both come on. Hazard switch replaced. Blinker relay replaced. Combi switch replaced. All light bulbs replaced. Still does it. Car's electrics were fine, and then car was sitting for about 6 months. Any ideas? I'm thinking somehow the blinker is telling the hazards to come on, but I've changed everything involved, or so I'm thinking.

Aquaticedge · #2 11-22-2009, 05:32 PM

Check the Fuses again, make sure there's no buildup,

Stevo · #3 11-22-2009, 06:59 PM

Might help too know what car you have.

Junkman · #4 11-22-2009, 07:26 PM

Do we have any better wiring diagrams? The 83-85SD diagram is attached. You've covered most things if the new parts actually TEST good. NExt step is grounds.

ImBroke · #5 11-22-2009, 08:37 PM

Sorry, car is the 85 300D. And I get on people for doing the same thing..

I know the stuff was good, because I took it out of a working car.

Stevo · #6 11-22-2009, 08:59 PM

You changed the relay under the console, forward of the shifter?

Yak · #7 11-22-2009, 09:32 PM

If you can, remove the left and right wires from the hazard switch (cleverly labelled 'L' and 'R') then plug it back in and try the combi switch. This removes the output power to each bulb at the hazard switch but leaves the supply line to the combi switch intact. If they both still come on, then the combi switch is faulty, if not, then the hazard switch.

If you can't pull just those wires from the back of the hazard harness, then leave the hazard unplugged but jumper the black/green/white wire (should be pin 49a, according to the wiring diagram) to 12V (probably the red/white wire at pin 30) and try the combi switch again. This will cut the hazard switch out of the circuit and you should be able to test the L/R selection of the combi switch. They shouldn't flash though, just come on steady.

ImBroke · #8 11-23-2009, 05:59 AM

Quote:

Originally Posted by Stevo

You changed the relay under the console, forward of the shifter?

Stevo, yes. Yak, I'll try that tonight.

ImBroke · #9 11-23-2009, 06:02 PM

Yak, with the schematic in front of me, it's easy to see. It's definitely the combi switch. Sucks that I just bought one. I'll try another one and see what happens. I should know better than to just throw parts at something without researching first. I keep forgetting I have the manuals on CD, but actuallly I didn't think they had wiring diagrams in there.

Spoke too soon. Took combi switch, and measured from blk/wht/grn to blk/wht and then to blk/grn when turning on the blinker. (out of circuit). Measures open til I turn that way, and then short. But, turn the other side on, and it's open. So, combi switch is good.

Just got back in,, and something interesting. The connector that the combi switch plugs into is sitting there staring at me. Pins 6-8 are shorted. Not good. Now I have to find out where.

Well, they are not shorted together, they are shorted to ground. Both 6 and 8. I have the connectors disconnected from bulbs, so no ground there. I am looking at the harness, and someone's been in there before. Nice.

ImBroke · #10 11-24-2009, 08:31 PM

Well, riddle me this. The problem is the speedometer head. Swapped it out, and good to go. Swapped the original one in and symptoms are back. I just fixed the odometer on that one too. Damn. Now I have to try to reset the milage on this one to match the old one. I never would have suspected the speedometer.

Jeremy5848 · #11 11-25-2009, 12:18 AM

Some kind of a short circuit between the left and right turn indicator lamps?

#12 11-25-2009, 12:37 AM

Quote:

Originally Posted by Jeremy5848

Some kind of a short circuit between the left and right turn indicator lamps?

Probably, or maybe a ground problem in the instrument cluster.

Yak · #13 11-25-2009, 07:13 PM

It's probably a short at the cluster connection. Check the solder joint on connections 13 and 14, or look at the circuit trace. You might see a tiny scorch mark if the lights were pulling current across a tiny conductor.

I'd spray the connectors with some compressed air to clear debris, then spray again with contact cleaner. Check the pins and the plugs closely. Maybe one is loose or bent.

ImBroke · #14 11-25-2009, 10:27 PM

After not believing what I was seeing, I spent more time on it tonight. Turns out the problem wasn't the speedo head, but the piece with the 3 gauges on it. Replaced that, and all is well again. And this time, it's sticking to working. That's ok, I think this car is going away soon. I'm not sure what to do with this car. It either gets an engine swap from Bruiser, or I cut bait and run.