Bad Turn Signal Relay or Instrument Cluster? [SOLVED]

[emerydc8]

I've been having some issues lately with my turn signals and I'm not sure if it's due to several bad relays or perhaps something in the instrument cluster itself is going bad. The turn signal clicking noise will sometimes get out-of-sequence with the flashing arrow. I replaced the relay in the under-hood relay module box and it seemed to have fixed the problem for about a week, but then the same problem cropped up and, this time, the signals and flashers eventually stopped working altogether.

This second replacement relay I'm on now seems to be starting the same out-of-sequence problem and I'm thinking it won't be long before the turn signals and hazard flashers stop working again.

Any thoughts on what could be causing it? Maybe something in the instrument cluster is bad and causing the relays to fail? Is there an additional relay that causes the clicking noise in the instrument cluster?

Admin edit: See post #23 for solution, root cause was a faulty fuel/oil/temperature gauge in the instrument cluster.

 

[gsxr]

Jon, my memory is foggy, but I think the big relay controls the actual blinking of the external lights... but the clicker is part of the gauge cluster, I think the fuel/oil/temp gauge pod? Do you have a spare F/O/T gauge (or entire cluster) to swap out for test purposes?

 

[emerydc8]

Do you have a spare F/O/T gauge (or entire cluster) to swap out for test purposes?

I have a cluster in my other E420 but that car has ASR. Does that matter?

 

[kwontumspeed]

If you haven’t already done this and before you go pulling the cluster etc the blinker circuit runs through the hazard switch. Swap it out from the E420 and test. That was the root cause to my wonky signal issues last year.

 

[emerydc8]

If you haven’t already done this and before you go pulling the cluster etc the blinker circuit runs through the hazard switch. Swap it out from the E420 and test.

Where is the blinker circuit?

 

[kwontumspeed]

Where is the blinker circuit?

I meant swap out the hazard switch. Probably would take 15-20m max to do so. Suggesting it before you go tearing other things apart for no reason if it is the switch.

 

[emerydc8]

I meant swap out the hazard switch. Probably would take 15-20m max to do so. Suggesting it before you go tearing other things apart for no reason if it is the switch.

I'll start there and swap the hazard switches. Didn't know there was a circuit inside the switch that controlled anything. Thanks.

 

[kwontumspeed]

I'll start there and swap the hazard switches. Didn't know there was a circuit inside the switch that controlled anything. Thanks.

Yeah I didn’t think so either. But I kinda found myself in your shoes hunting it down with relays, cluster, etc. then happened to find a post about it. My blinker was getting out of sync. It would also act up (light but not blink, blink erratically, etc) but then work flawlessly for a little bit. Then all of a sudden, dead.

 

[emerydc8]

I just swapped the hazard switches and I'm still getting the problem on the same car. So that didn't seem to work for me.

 

[Twilling]

The little speaker for the turn signal sound is on the backside of the fuel/oil/temp gauge. Maybe a bad soldering.

 

[emerydc8]

The little speaker for the turn signal sound is on the backside of the fuel/oil/temp gauge. Maybe a bad soldering.

I think I'll swap the entire instrument clusters between the two cars, presuming the plugs are the same. (Only one has ASR.) I'll check the little speaker in the process. I don't know if that part is available separately or if I would have to buy an entire used instrument cluster.

 

[gsxr]

I have a cluster in my other E420 but that car has ASR. Does that matter?

For test purposes, the non-ASR cluster will work fine. The only difference is the two missing ASR lamps, which are irrelevant to the turn signals.

The clicker/speaker is a small component on the circuit board. I forget what it looks like, or if that alone could be the issue. There might be other circuitry on the PCB causing the issue. If swapping clusters cures the problem, all you need is the F/O/T gauge pod. This can be from any 1992-up sedan as a donor; or older than 1992 if you don't mind the "economy" needle added at the bottom.

 

[emerydc8]

I'm looking at an instrument cluster from a 1994 E320. Any thoughts on whether the fuel quantity gauge will indicate correctly if I install it in my 1995 E420?

 

[Jlaa]

For test purposes, the non-ASR cluster will work fine. The only difference is the two missing ASR lamps, which are irrelevant to the turn signals.

The clicker/speaker is a small component on the circuit board. I forget what it looks like, or if that alone could be the issue. There might be other circuitry on the PCB causing the issue. If swapping clusters cures the problem, all you need is the F/O/T gauge pod. This can be from any 1992-up sedan as a donor; or older than 1992 if you don't mind the "economy" needle added at the bottom

If you get

I'm looking at an instrument cluster from a 1994 E320. Any thoughts on whether the fuel quantity gauge will indicate correctly if I install it in my 1995 E420?

I believe I read @gsxr indicate that the 034 has a 70L tank, in which case the gauge would read properly. Even if the 034 did not have a 70L tank, it is not a big deal to DIY recalibrate the fu gauge.

 

[emerydc8]

The cluster is on its way. I looked for the individual F/O/T gauge pod on Ebay but the sellers were from overseas (Russia, Albania, etc.).

 

[gsxr]

I'm looking at an instrument cluster from a 1994 E320. Any thoughts on whether the fuel quantity gauge will indicate correctly if I install it in my 1995 E420?

Yup! The E320 F/O/T pod will work fine in your E420, assuming it is good. They should even be the same part number.

 

[emerydc8]

Yup! The E320 F/O/T pod will work fine in your E420, assuming it is good. They should even be the same part number.

Got the new unit and it's definitely different than what's in my 95. Now, I guess I need to see if I can swap only the left cluster.

 

[Jlaa]

Got the new unit and it's definitely different than what's in my 95. Now, I guess I need to see if I can swap only the left cluster.

Yeah! The left cluster is the same part number - 124-542-43-01 !

 

[emerydc8]

Yeah! The left cluster is the same part number - 124-542-43-01 !

Problem is the left cluster is hard-wired to the right cluster. [EDIT: Jlaa is right -- The wires run to the prism card, which is not connected to the tach]. I swapped out my old speedometer/odometer into the unit I just got today Hopefully it will work. Will advise.

[EDIT]: I noticed my old right cluster is marked 8ZYL / 4TAKT and the one I got from ebay (that I plan to install) shows 6ZYL / 4TAKT. Obviously that came from an E320 so I don't know if it would matter. It is a different part number but I think the plugs are the same. The salient difference is the redline -- 6400 (6ZYL) v. 6000 (8ZYL).

 

[Jlaa]

Problem is the left cluster is hard-wired to the right cluster. I swapped out my old speedometer/odometer into the unit I just got today Hopefully it will work. Will advise.

Oh! That's weird. Doesn't it all just come apart? (Ignore the twisty aftermarket wiring I was deleting when I opened everything up). If you swapped the speedometer from the original housing to the new-to-you-used-housing, make sure that the new-to-you-used-housing has the updated nightime light prisms so that you can see at night.

At some point in the w124's history, MB redesigned the light prisms in the instrument cluster housing. Earlier models had super dim prisms, so people put higher wattage bulbs in them, which would only melt the plastic of the prisms.

 

[emerydc8]

Thanks. How can I tell if I have the updated prism lighting?

The left and right clusters are joined by the three red/black, and black wires on the top. In my pic above, you can see the three wires soldered to the upper left side of the left cluster (right side in the pic). [EDIT: The wires run to the prism card -- not the tach]. Jlaa is right -- The tach slides right out.

 

[Jlaa]

Thanks. How can I tell if I have the updated prism lighting?

The left and right clusters are joined by the three red/black, and black wires on the top.

From @gsxr's website, which I've mirrored locally:

 

[emerydc8]

Thanks! Figures Dave would have discovered this! I had it bolted back together so I decided not to check for the updated lighting. I installed the cluster and it works well. Actually, the left and right side seem to be a bit brighter than the center. Thanks for all the help. BTW, the turn signals and blinkers are now in sync with the clacker, so it was the cluster that was causing the problem.

 

[gsxr]

Jon, the F/O/T gauge does have wires going over to the other side, but it all will swap around. You only need the F/O/T pod.

I'm surprised the M104 tach works at all in the M119... not sure if it will read accurately? If so, you could leave it alone. Otherwise, swap that out. The 900rpm warm idle indicated in the photo looks wrong, should be ~650.

All housings after roughly 1990-ish should have the "improved" light guides. Good news is, your turn clicker is fixed!

 

[emerydc8]

Thanks, Dave. I'll keep an eye on the engine idle. I think the higher idle might be caused by a broken throttle cable adjuster screw from my kneeling in the engine compartment in the process of changing out the a/c blower motor and regulator a few days ago. Luckily, I have two throttle cables in my parts hoard, so I'll be changing the cable out this weekend. I cracked a few of the petrified black breather hoses as well, so I know I have a vacuum leak going, until I get the replacement hoses.

 

[gsxr]

Jon, I think the 6-cyl tach has a different signal frequency, so it may not read accurately with a V8 input. But, I don't know for certain as I've never tested this combination. Note the V8 gauge is marked 467Hz, and the 6cyl is 350Hz, and 350/467 = approx 3/4, which would match the change in cylinder count...

 

[nocfn]

All this cluster talk I would like to ask. Any of you have the stomach to part with the plastic cover on the left side of a cluster? It covers the light arm. My Dad lost his

 

[emerydc8]

Thanks, Dave. You're right about the tach being off. At 45 MPH it seems to be indicating probably 500 - 750 RPM more than it should. I'll have to pull it out and install my old tach into the new (to me) cluster.

 

[emerydc8]

Oh! That's weird. Doesn't it all just come apart? (Ignore the twisty aftermarket wiring I was deleting when I opened everything up). If you swapped the speedometer from the original housing to the new-to-you-used-housing, make sure that the new-to-you-used-housing has the updated nightime light prisms so that you can see at night.

At some point in the w124's history, MB redesigned the light prisms in the instrument cluster housing. Earlier models had super dim prisms, so people put higher wattage bulbs in them, which would only melt the plastic of the prisms.

I was wrong about the wires connecting the left and right cluster. The wires actually run to the prism cards on the tach. The tach came right out -- No wires are connected to it.

Regarding the updated lighting prisms, the used E320 cluster I got from ebay seems to be good, but I'm not sure if it is the newer style. It looks like it was made in 1993 (5393). The cluster I removed from my car (2594) may be the old style, but even if it isn't, it looks like someone put a brighter bulb in it and melted the socket, just like you explained. In any case, all is well now. The car is idling at 650 RPM with the old tach reinstalled. Thanks to everyone for the help.

 

[gsxr]

Yep, the overwattage bulbs melt the prism, making the visibility problem worse. Your eBay replacement is the newer/updated style, which I think appeared in the late 80's or early 90's, but definitely by 93. Good to hear it's all fixed now.