Right Turn-signal Flashes Left - PeachParts Mercedes-Benz Forum

Foleydb · #1 12-12-2002, 06:23 PM

Summary: I get left turn signal lights all around and on dash when turn-signal lever is in either left OR RIGHT position.

Detailed Explanation: The problem started a couple of days ago in my '97 S-500 with 57K miles. When I turned on the right turn signal the right arrow on the dashboard flickered for a moment or two and then the left arrow began to flash as if I had selected for a left turn. I tried operating the right turn signal a dozen or so times during the journey, but each time I got a left turn signal. The left turn signal works normally. By the time I got home the brief flickering of the right dashboard arrow had ceased when initiating a right turn signal and the left signal arrow was all I got. When I moved the lever to either right or left turn position I got a normally blinking left dashboard arrow. In the garage I checked and found that all of the left turn signals on the outside of the car also flash normally when either the right or left turn signal lever is engaged.

Bought a '97 S-500 a couple of months ago, and it is now my turn to learn about Mercedes maintenance first hand. I don't have a mechanic in the DC area, but I have had negative parts experience with HBL and wouldn't go back there again for any reason. American Service Center wanted 3 times the appropriate price for some minor body work that was done elsewhere to perfection, so I am feeling quite wary.

So, do I just leave it with someone to "look at", or should a good mechanic know from the description above what is wrong and how to fix it? Is this a good verbal test of a prospective mechanic to see if he knows his business with a W-140? Any thoughts?

Thanks in advance to all who respond.

Benzmac · #2 12-12-2002, 08:31 PM

You may have the wrong bulb or a loose socket in the rear...Some rear lights are special to the Mercedes. LOOK very carefully at the tabs.

Gilly · #3 12-12-2002, 08:44 PM

I had EXACTLY this problem on a similar year SL just a week or two ago.
The signal from the combination switch to the combination relay is similar to a voltage coded signal (voltage coded may be the incorrect description), but in effect, one direction siganl is a direct voltage through the switch, the other direction is sent through a resistor in the switch itself. The combination relay looks at the voltage from the switch and determines if the switch position indicates left or right. To clarify what I am saying, there is only ONE wire from the switch to the combination relay which is used to relay a right or left turn. There is NOT a left wire and right wire!
Ultimately, what I found was that I had a very low voltage going into the switch, which was traced back to the ignition switch itself.
When it fails, you can monitor the voltage at the fuse for the turn signals and see if it is too low, I had about 4.5 volts when it was in a failed state. I then jumped a good 12 volts into the top of the turn signal fuse and Voila! normal turn signal operation. After figuring it out, then i noticed I could make the problem occur and disappear by tweaking the ignition key in the switch a little bit.
A new ignition switch fixed it. I believe the S class in question and the SL I worked on use the same style ignition switch.

Gilly

Foleydb · #4 01-25-2003, 11:52 AM

After reading the posts about finding a good shop in the Washington DC area I took my S-500 to Don Pool Mercedes-Benz Repair. They dismissed the fix suggested by the moderator GillyBenzTech and indicated they thought he was clueless. They inspired zero confidence by both their manner and comments, and I was filled with doubt about leaving the car with them.

Lo and behold they charged me $227.51 and told me the problem was the "Combination Relay Module" was bad. This part is in the rear part of the fusebox under the hood, and is not easily accessible the way all the regular fuses are. The part number is 140-820-7626. They want $325 for the part and $97.50 to install it.

Here is exactly what they said they did to it:
Install laptop & perform quick test. No codes present pertaining to turn signals. Trace/isolate & pin test electrical system & found combination relay module bad.
By-pass module & found right turn signals operating.

Phil at the on-line parts seller here at MercedesShop.com says the part lists for $304 and he can sell it to me for $269 delivered.

I have several questions:

1) Since parts are not returnable, can I have confidence that this is indeed the problem?
2) If I order the part, can I install it myself?
3) How should I feel about what Don Pool Mercedes charged me for supposedly isolating this problem - 3 hours at $75?

Any thoughts are very welcome.

Gilly · #5 01-25-2003, 04:12 PM

Clueless, huh? Buy that relay module so I can call them up and laugh at them when it doesn't fix it.

Gilly

Gilly · #6 01-25-2003, 04:46 PM

Sorry, pretty upset about this, especially since if they would read my comments, they can understand how this can happen. Plus, since I had EXACTLY this problem just days before you posted your question, I know it can happen. I believe the 129 and 140 turn signals work essentially the same way.

A simple test would be to locate the fuse in the fuse box for the turn signal and see what the voltage is with either the key "on" or the engine running. It should be battery voltage. If it is significantly lower, (like around the 4 or 5 volt range, anything significantly lower than say 10 volts anyways) I would say this warrants further diagnosis. Now, the best part is that you can actually verify this also. By using a jumper wire to go from a neighboring fuse with a good voltage present, and jumpering to the turn signal fuse, see if the turn signals are operating correctly.

In your case, I would admit that without personally examining it, i can't say for sure that this is the problem (again, in this car that I worked on, it was the ignition switch), but it definitely was the problem on the car I worked on.

Please keep us posted.

Gilly

myarmar · #7 01-26-2003, 12:28 AM

This is a portion of the schematic in question for MY 97.
S4/s1 - turn signal switch,
N10 - combination relay.
As Gilly said there is only one wire from the switch to the relay. If the voltage on the fuse 15 in the fuse box F3 was OK
I would try to get the meter on this wire either on the X1-9 connector or on the combination relay N10-3 and check voltage with turn switch in Left and Right positions. You should see different readings.
Also with X1 disconnected the resistance between X1-11 and X1-9 should be 0 Ohm in Left (Right?) and some resistance in Right (Left?)

Gilly · #8 01-26-2003, 09:43 AM

From a "mysterious source" (who's name I could give you, but I'm a nice guy) I was informed that the test procedure involved something like this:
"Test, test, test, then decide that they have a substitute combination relay, plug that in and it fixed it", so they come to the conclusion that it's the relay.
One wonders, if a substitute combi relay was available, why that wasn't tried first, as it certainly would have beeen "the silver bullet" in discovering the problem and saved everyone alot of time (among other thing$).
Thanks for your comments myarmar. What I discovered in this process is when it's in the failed state, you can jump good battery power to the small "test spot" on the top of the plastic fuse and the signal will immediately start flashing on the appropriate side.

Gilly

Foleydb · #9 05-18-2004, 04:51 PM

Just wanted to finish this. Got back in country after being away a while and got this fixed for one hour's labor at American Service Center in Arlington, VA., a first-class dealer operation. It was not the relay that Don Pool Mercedes Repair charged me three hours of labor (227.50) to tell me they could replace for another $500. I should have walked after five-minutes talking to the guys at Don Pool. I thought they were shady and didn't know what they were talking about, but didn't listen to my own warning bells. Anyway, ASC fixed it fast by replacing the faulty combination switch, and from start to finish charged an hour of labor. They never touched the allegedly faulty combination relay that Don Pool's mechanics wrote in their report "found combination relay bad". What B.S.!

Anyone who reads this and still takes their car to Don Pool in the Washington DC area can only blame themselves. They should pay me back the $227.51, but I don't expect honor from -------.

gti_intherye · #10 08-24-2004, 05:27 PM

(bringing the thread back with a wordy post)

I just got my 96 S420 back from Claridge's Mercedes in Fremont, California for the same exact turn signal problem (signal left or right, exterior lights blink left). After about a week in the shop, they quoted the same price as described above for the combination relay (P/N: 140-820-76-26) with the same price for labor. However, the work order lists the item as a "control unit."

Needless to say, the problem was fixed. I was just wondering if the problem could have been fixed alternatively with the above mentioned solutions with the ignition switch or the combination switch.

Also... I had a question about a TSB posted on alldata.com for a MIL for a failed exterior lamp without any failed lamps upon inspection. What has been done to cure this problem? I need that MIL cleared so that I can retest/pass smog. The car passes emissions easily but fails at the diagnostic scan. The mechanic tells me that the scan never completes its cycle. The inspection report reads: "This vehicle failed the MIL/Check Engine Light due to failure to successfully complete all OBD self tests." Could any of these issues with the lighting be related to this smog issue?

TIA

gti_intherye · #11 08-25-2004, 01:28 PM

bump! I need to smog the car soon

Mistress · #12 04-05-2006, 12:16 PM

Foleydb- Just a note of thanks for the warning about Don Pool Mercedes Benz I was getting ready to take my 420 SEL for a good check out...ASC is right down the street from me, I'll go there. Thanks.