Help, Intrument cluster and relay unit K40 replaced still no working gauges - PeachParts Mercedes-Benz Forum

Texholdem · #1 03-16-2009, 10:13 PM

Hi all,
I am used to getting few or no reply but this time I really need more inputs than last time.

My instrument cluster has no gauges working. All other elements are OK, that means when I turn the ignition key to position 2, all warn signals for ABS, BRAKE, ETS, Seat belt, CHECK ENGINE are on. After starting the engine they are off as expected, except for the parking brake signal. (pic 1 & 2)

Backlight illumination for headlight, as well as turn signal, high beam indications are working fine. All pixel displays for trip odometer, odometer, outside temperature and clock are on and no missing pixel.

The big issue are the needles of the gauges for engine temperature, fuel level, speed (when moving) and rmp (pressing gas pedal at neutral position "P"), all 4 needles are dead. The needle for speed vibrates a little but does not leave the resting position.

I replaced the cluster with a used but otherwise supposedly working one, same error. Then someone suggested that the relay unit K40 could be the cause; I bought a new one from ***************, replaced the old one today without success (pic 3). I also made sure that the connectors are firmly attached to the cluster, reached into the cavity behind the connected cluster and wiggled every cable harness to see if there is some loose contact.

Now I really do not know what to do. Normally when I got no reply I accept quietly that my question is either stupid or difficult :p:, now I am giving it another try and hope for some help.

In pic 4 is the wiring diagram for the group of needles, it is not clear to me as to which pin from the connector goes to which gauge.

If I had to take my car to dealership, what do you think it will cost me?

Please give your comments, every input is highly appreciated, be it a sympathy or consolation

Texholdem · #2 03-17-2009, 12:38 AM

I removed the cluster and measured the voltage at the two connectors. The first picture show the measurement of the left connector, the second picture for the right connector:
Left connector has power only at pin C1 (11.6 V) and pin L2 (7.47V) and that is suspicious too few pins.
Right connector has power at pin A6, 8, 9, 11 and B3.
Can someone interprete the measurement, is power missing at some pin? especially of the left connector?

The minus "-" sign at the pins means 0.0 V was measured, probably ground.

Texholdem · #3 03-17-2009, 08:02 PM

New voltage measurement at right connector A-B with engine hot and running, headlight on, applying middle pressure on gas pedal .

A6: 13.22 V
A8: 12.45 V
A9: 13.04 V
A11: 13.2 V
A13: 13.2 V

B1: surges from 0 to 13.98 V with gas pedal
B3: 7.36 V instead of 10.67 V measured yesterday with engine not running

Ground at A3 and A12 very good.

What do the numbers mean?

professor · #4 03-17-2009, 09:06 PM

I am not familiar with new systems but I have a feeling that it needs to communicate with something to display STORED data such as mileage. You may need a computer interface to transfer the data. Can some of the new Benz people shimy in?

professor · #5 03-17-2009, 09:08 PM

This also can happen CLICK on second hypothesis

http://web.engr.oregonstate.edu/~shuman/InstrumentCluster/index.html

Matt L · #6 03-17-2009, 09:42 PM

Well, it is very likely not that, because the rear of his cluster looks nothing like what you're seeing there. The W210 has locking tabs holding the cables secure.

However, I did enjoy the first step:

Quote:

1. Sit in the drivers seat and find the steering wheel that is shown in figure 7.

He proceeds to take the wheel off. Fortunately, US-spec W210s all have adjustable steering wheels. If you put the wheel all the way down and back, the cluster comes out easily.

Texholdem · #7 03-17-2009, 10:41 PM

Thanks professor and Matt, as a matter of fact I have had these days a lot of practice in removing and reconnecting the cluster board. Yesterday I removed it to measure voltage at the connectors. Put it back together, took the car to work and back home. In the evening I disconnected it again to measure with running engine to take other numbers. Every time I reconnect the unit I make sure that the connectors firmly sit. Actually since two weeks I have done it at least 10 times, alternatingly with two clusters in the hope of getting some clue; now I have even the instrument cluster loosely sit, not pushed in all the way so that I can take it out with no hooks, just bare fingers.

I need guidance as to if the voltages at the connectors are OK or not. If they are OK then the fault may be the cluster unit. I would dread searching the fault in the jungle of wires behind the cluster.

All fuses related to the cluster have been replaced as well as the relay K40.

Texholdem · #8 03-18-2009, 09:52 AM

This morning I could see that the instrument cluster was working and in perfect condition during the 30 min ride to work, all gauges were fine for speed, rmp, ECT and fuel level. Parked the car, turned engine off and retried many times ... no needles moving.

So it must be a loose contact somewhere, pulled out the cluster but did not disconnect the connectors, wiggled, wiggled, wiggled all reachable cables in the cavity behind the steering wheel, nothing changes.

That is very frustrating since I don't know where to look for this elusive failure. I'd rather have a defective part than that.

gschira · #9 03-20-2009, 07:34 PM

Texholdem,
Thanx for the reply to my instrument cluster question. My car did just fine this am. Again, however, when leaving work---Same ole stuff. Buzzer first within 300 feet of starting engine, cluster fine. Then within half mile cluster goes bonkers. This time the cluster didn't come back to life until I had traveled about 16 miles. Then went out again then revived again. Sure is weird.

gschira · #10 03-20-2009, 07:34 PM

Texholdem,
Thanx for the reply to my instrument cluster question. My car did just fine this am. Again, however, when leaving work---Same ole stuff. Buzzer first within 300 feet of starting engine, cluster fine. Then within half mile cluster goes bonkers. This time the cluster didn't come back to life until I had traveled about 16 miles. Then went out again then revived again. Sure is weird.

gschira · #11 03-20-2009, 07:37 PM

Not sure why that reply showed up twice, must be tied to my instrument cluster.

Emcdonalds · #12 12-22-2009, 08:12 AM

After many hours of trawling the net, I finally find someone with a case similar to mine , the cluster is dead most of the time and once in a while, would work perfectly. Then the speedometer would rattle incessantly when all gauges are dead.

I read this thread and like to ask was the issue solved and how was it solved ?

Thanks !
emc