w123 300d - no climate control lights - Page 2 - PeachParts Mercedes-Benz Forum

Graham · #16 01-15-2012, 04:24 PM

Quote:

Originally Posted by my123ca

In my case, I have a short on the left rear door harness. What i did was to put a 1 amp fuse on the blue wire between the instrument cluster and the center console. Everytime i used the left rear door, it would blow the fuse. I unplugged the left rear switch for now until i can fix the harness. Same thing happened to me with the broken traces but i only soldered them together using thin telephone wires-not jumping from pin to pin.

Not sure how the door harness and the console are related? Don't they come off different fuses/circuits?

my123ca · #17 01-16-2012, 01:09 AM

Quote:

Originally Posted by Graham

Not sure how the door harness and the console are related? Don't they come off different fuses/circuits?

The blue wire is used by the lights on the switches including the switch on the door. The blue wire starts in pin12 which get its power from pin11. Its on page124 of the electrical manual.

Graham · #18 01-16-2012, 09:57 AM

Quote:

Originally Posted by my123ca

The blue wire is used by the lights on the switches including the switch on the door. The blue wire starts in pin12 which get its power from pin11. Its on page124 of the electrical manual.

Ok, Sorry. I didn't realize you were just talking about the wire to the LED in a rear door window switch. Presumably that wire must be grounding somewhere.

Yak · #19 01-16-2012, 03:05 PM

Quote:

Originally Posted by Graham

I am going to pull it and have a look once it warms up a bit here (zero F here tonight!). The wire was just installed so I can't see there being any wear. But something must be wrong!

The ground wire that has to be disconnected when the cluster is removed goes to that screw tab, so I figured it should be a good spot!

I was a bit puzzled as to why they needed a separate ground going through pin 15. But maybe that is the main ground and the one I used is just an additional one. Once I have it out, I will follow the traces and perhaps run the white wire to where it should have gone!

The temp gauge only seems to be grounded out in the engine bay. When key is turned on, it goes from zero to full scale.

Bill Hunter wrote in the DIY General forum:
"Field expedient upgrade:
On the rear of the fuel gauge circuit board there is a square tab (screw mounts through it) grounding the speedometer assembly.
Make/install a ground wire with two spade connectors in the center, mount it from the square ground point to a solid body ground.
This reduces/eliminates most instrument cluster electrical issues.
The spade connectors in the center of the home made ground wire are for easy instrument cluster removal in the future."

Seems to imply that that tab is a good ground point.

If the traces in your cluster are that blistered, it's possible that one of them is sticking up enough to contact the temp gauge. I think the two vertical posts are for the temp gauge. The hole between the posts appears to follow a trace around for ground, so grounding the case might be correct, but if the blistered line carries a supply, that may fooling the gauge.

If it appears to be shorting in the engine bay, I think you can simply pull the wire off the sensor in the block and see what happens.

Since your fuel gauge works on the same principle, is that also reading in error? If so, then it would seem to be a cluster problem. If not, then maybe a sensor (or wire) problem.

Graham · #20 01-16-2012, 03:58 PM

Quote:

Originally Posted by Yak

If the traces in your cluster are that blistered, it's possible that one of them is sticking up enough to contact the temp gauge. I think the two vertical posts are for the temp gauge. The hole between the posts appears to follow a trace around for ground, so grounding the case might be correct, but if the blistered line carries a supply, that may fooling the gauge.

If it appears to be shorting in the engine bay, I think you can simply pull the wire off the sensor in the block and see what happens.

Since your fuel gauge works on the same principle, is that also reading in error? If so, then it would seem to be a cluster problem. If not, then maybe a sensor (or wire) problem.

Thanks for the interest.

I had the cluster out again. I had previously cut off the burned trace ends so they should not have been a problem. There is a threaded stud that goes through the hole between the two pins. Same for the fuel gauge. Tightening the nuts on those studs pulls the gauge onto teh pins and holds it there. I did notice that the nuts were not tight. I must have forgotten to tighten them. That is the only thing I found wrong.

While I had the cluster out, I rerouted the wires. I ran the 15 ground to the far end of it's trace (But that is connected to other ground I used, so that won't do anything, I don't think. I ran the power to the dash bulbs directly so as to eliminate the lighting traces altogether. Again, should make no difference.

While out, I checked the dash bulb housings - they were not bad, just slightly discoloured. I tried several cleaning methods without success, so tried something else - I cut some small pieces of aluminum HVAC foil tape (used for sealing ducts) and stuck them in there as reflectors. Hope the glue holds up. It is supposed to. Also sealed the outside of the light ducts on top of the cluster.

Graham · #21 01-16-2012, 05:03 PM

UPDATE: The temp gauge now at least doesn't swing to max when I turn teh key on! Too cold to know if it is working because it is a bitter night here and car is not going out!

Good news is that my dash lights are now bright! Seems like that reflective tape (and eliminating light leakage from the tunnels) made quite a difference!

Yak · #22 01-16-2012, 07:23 PM

Quote:

Originally Posted by Graham

UPDATE: The temp gauge now at least doesn't swing to max when I turn teh key on! Too cold to know if it is working because it is a bitter night here and car is not going out!

Good news is that my dash lights are now bright! Seems like that reflective tape (and eliminating light leakage from the tunnels) made quite a difference!

I did a similar reflective tape update in my cluster rebuild. Pics are in the pdf in post #10 here. Painting Cluster Needles

It's possible that the temp (and probably fuel) gauge need a reference ground and if it wasn't tight then maybe the temp gauge was reading high. That center mounting screw/post appears to be connected to the ground trace at some point. If it was loose, then maybe that's the explanation.

I played around with one of the images of a burned trace and the center posts between the variable resistance gauges (temp and fuel) are connected, and then appear to connect around to at least the high beam ground - and from there probably on to more of the ground path. The angle and the color is poor in the image, so there's no guarantee those traces are correct. For the pic:

1 = hi-beam +
2 = temp ref ohms
3 = fuel ref ohms
4 = sender side of low fuel bulb
5 = temp/fuel +12 v and others (brake bulbs, low fuel bulb) trace is not complete.

Graham · #23 01-16-2012, 08:13 PM

Quote:

Originally Posted by Yak

I did a similar reflective tape update in my cluster rebuild. Pics are in the pdf in post #10 here. Painting Cluster Needles

It's possible that the temp (and probably fuel) gauge need a reference ground and if it wasn't tight then maybe the temp gauge was reading high. That center mounting screw/post appears to be connected to the ground trace at some point. If it was loose, then maybe that's the explanation.

That trace between the temp/fuel gauges shows on the cct diagram - at first I didn't understand what those extra connections were

I played around with one of the images of a burned trace and the center posts between the variable resistance gauges (temp and fuel) are connected, and then appear to connect around to at least the high beam ground - and from there probably on to more of the ground path. The angle and the color is poor in the image, so there's no guarantee those traces are correct. For the pic:

1 = hi-beam +
2 = temp ref ohms
3 = fuel ref ohms
4 = sender side of low fuel bulb
5 = temp/fuel +12 v and others (brake bulbs, low fuel bulb) trace is not complete.

It could have been those loose nuts that were the problem. I am still puzzled as to what caused the traces to blow in the first place. I checked everything I could with a meter but could find no grounded connections. My car will soon be put away for the rest of the winter so I may not find out if there is still a problem for some time.

I also started to trace the PCB, but gave up. Hard to follow the traces that go through the black areas. The wiring diagram does identify most of the pins.

One strange thing I noticed, was that the dash light on the main board has a black background (totally non-reflective) while the one on the end of the wires has a white background.

BTW - Excellent write up on cluster refurb in your link!

Graham · #24 10-05-2013, 01:49 PM

Have same problem back again on 85 300D

Fuse 1 blows and I lose dash/console lights and passenger side marker lights.

Have done a lot of testing.
- With cluster unplugged, fuse does not blow and then marker lights work, shift light works, alarm buzzer all work.
- Removed Cluster and found it does not have a short (pins 11 or 12 to ground). (Power passes through cluster from pin 11 to pin12 of plug which then supplies 12v to console lights, hazard light bulb and window switch led illumination
- With lights on, cluster out, measured 12V between pin sockets 11 and 12 of cluster plug which seems to indicates a short somewhere beyond pin 12. But measuring resistance to ground on pin 12 indicated 3.5ohms which doesn't seem like a short (used two different meters)!

I guess I will try disconnecting downstream systems one at a time

But could be a chafed wire back under the console somewhere

Driving me nuts - again!

Graham · #25 10-05-2013, 05:39 PM

Well everything is working again, but as before, I don't know why. I put in test light between sockets 11 & 12 of the cluster plug. It came on dimly, as it should, when lights were turned on. Console lights worked. Tried pulling door & hazard switches. Made no difference. Replaced test light with jumper. Fuse held and console lights still on. Re-installed cluster and now everything works. This after blowing fuses several times before taking things apart. No obvious chafed wires. No clue why it now works! But what the heck. Let's see how long this works!

my123ca · #26 10-05-2013, 11:03 PM

Tried opening the doors and windows yet?

Graham · #27 10-06-2013, 10:41 AM

Quote:

Originally Posted by my123ca

Tried opening the doors and windows yet?

Front door was open while I was doing work. Front automatic courtesy light is for some reason not working, but manually it is. Rear courtesy light is working. None of those circuits come off fuse 1.

Window motors are not on same circuit either, just the switch leds. Thinking the leds or the switches themselves might have failed, I pulled each window switch during testing with no change in test light brightness.

From the tests I did it seemed problem was somewhere beyond pin 12 of the cluster which means console illumination or window/hazard switch illumination. Yet all of that is now working again???

I guess I should be happy, but it will no doubt happen again.

my123ca · #28 10-06-2013, 12:57 PM

Quote:

Originally Posted by Graham

From the tests I did it seemed problem was somewhere beyond pin 12 of the cluster which means console illumination or window/hazard switch illumination. Yet all of that is now working again???

I guess I should be happy, but it will no doubt happen again.

In my case, everything would work good until i open the left rear door or window. Hope you found the problem.

cooljjay · #29 10-06-2013, 02:59 PM

Have you ever removed the bundles of ground wires behind the cluster and cleaned them?

Its important to clean all the ground contacts in the car as normal maintenance.....there are two in the trunk, one near the gear shifter, bundles behind the cluster, one near the passenger headlight, ground strap and battery to chassis ground......dirty grounds can cause all sorts of issues....

Graham · #30 10-06-2013, 03:07 PM

Quote:

Originally Posted by my123ca

In my case, everything would work good until i open the left rear door or window. Hope you found the problem.

Well, not knowing why my dash lights now worked, I decided to start testing your way

First door I opened was driver side passenger. Guess what - dash lights went off! Blown fuse!

On both rear doors, courtesy light still works. So what is there in a rear door that would cause fuse 1 circuit to short? Perhaps the window switches have a light and the harness to the door is chafing?

How did you fix the problem?