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  #16  
Old 11-26-2003, 07:50 PM
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N. Hodges,

All of my bulbs were twist-out bulbs. I took each one out and tested it with a DVM. I looked the mother board over pretty carefully and didn't see any bulbs on the board itself.

Ed

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  #17  
Old 11-26-2003, 08:22 PM
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Instrument Cluster Self-Test

Nobody else has mentioned it. So--since we are talking about instrument cluster problems, I thought it best to point out the "Self-Test" capability that the instrument cluster has.

The following assumes that you have a digital display for odometer, trip meter, and outside temperature. There's a similar process for the analog displays but it may differ slightly:

1. Start the engine
2. On the RH twist knob (i.e. the one that you use to set the clock, press on the very center of that knob for five seconds (with the end of a paper clip or a stiff wire).
3. The odometer display will then show "-----"
4. Then pull out on the RH knob and turn it to the right. Each time you do this, the cluster will cycle through a sequence of 9 test modes, as follows:

Test mode 1: Shows fuel tank contents in liters on odometer display (e.g. 1 80 indicates test mode 1 and 80 liters); shows "SE" on trip odometer for standard fuel tank.

Test mode 2: Shows momentary fuel consumption in liters/hour (e.g. 2 3_4 indicates test mode 2 and 3.4 liters/hour).

Test mode 3: Shows engine oil pressure in bars (e.g. 3 2_0 indicates test mode 3 and 2.0 bars of oil pressure).

Test mode 4: Shows engine RPM (e.g. 4 600 indicates test mode 4 and 600 RPM).

Test mode 5: Shows engine oil level (e.g. 0 indicates OK and 1 indicates Not OK).

Test mode 6: Oil pressure, fuel consumption, fuel tank, speedometer, and tachometer all go to 1/4 guage positions.

Test mode 7: Oil pressure, fuel consumption, fuel tank, speedometer, and tachometer all go to 2/4 guage positions.

Test mode 8: Fuel consumption, fuel tank, speedometer, and tachometer all go to 3/4 guage positions. Oil pressure remains at 2/4 guage position.

Test mode 9: Fuel tank, speedometer, and tachometer all go to 4/4 guage positions. Oil pressure remains in 2/4 guages position. Fuel consumption remains in 3/4 guage position.

The cluster will exit from test mode when the car is restarted.

Ed


1992 400SE; 119,000 miles
1971 220D (Sold)
1970 220D (Sold)
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  #18  
Old 11-26-2003, 08:47 PM
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Tachometer Still Has the Yips

Despite my cheery posting earlier hoping that the fuze cleaning process had cured my "bouncing tachometer" problem, my tachometer and oil pressure gauge still have the "yips".

As Gabby had recommended, I cleaned all the fuzes and fuze sockets. I've even cleaned the three fuzes in the top of the Base Module. And for awhile, things seemed to be much better. The oil pressure guage and the tachometer were stable. Then suddenly they got the "yips" again---down to zero for awhile--then back to normal for awhile.

My oil pressure gauge fails the Mode 6 self-test (describe in an earlier post). It goes to zero--when it is supposed to go to the 1/4 gauge level.

I think I'll try the Mode 4 self-test (RPM) and watch until my tach gets the yips and goes to zero. The digital display will confirm that I've still got the TNA (engine speed signal) coming to the instrument cluster. If that happens, then the instrument cluster is going to one of the shops mentioned in this discussion.
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  #19  
Old 11-26-2003, 09:15 PM
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Inst Cluster

Ed Hannah

I looked at Mitchells Manual and there does not appear to be any bulbs on the board. All of them do appear to be of the
twist in/twist out variety. The Mitchell Manual CD does not have a wiring diagram but it shows an exploded version of the cluster.
do you know how the analog version of the test you mentioned works.

Anyone?
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  #20  
Old 11-27-2003, 01:14 AM
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If you happen to have the instrument cluster with the analog odometer and trip odometer, the self-test readouts will appear on the (digital) Outside Temperature display.

The numbers to the right of the decimal are the test mode numbers (1-9); the numbers to the left of the decimal point are the data.

The self-test is initiated in the same way as described for the digital version. The test modes (1-9) perform the same functions in both versions (1 is fuel tank amount in liters; 2 is instantaneous fuel consumption but must divide readout by 10, 3 is oil pressure in bars but must divide readout by 10, 4 is engine RPM but must multiply readout by 100, etc.).

Ed
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  #21  
Old 11-27-2003, 12:50 PM
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Instrument Cluster May Not Be the Problem

As reported in a previous post, I put my instrument cluster into Mode 4 self-test which provides a digital engine RPM readout. Then I waited for the "yips" to occur--with my tach falling to zero.

And so it did (i.e. the tach fell to zero)--but my digital engine RPM display also fell to zero--indicating the loss of the TNA (engine speed signal) from the Base Module (N16/1).

So, I'm forgetting about any possible instrument cluster problems and focusing on Base Module.

The OBD I diagnostics have been telling me that the TNA signal from the Base Module is bad. Of course, I don't want to believe that--because of the cost of the Base Module. I've pretty much exhausted other possibilities and am back to the Base Module as the likely culprit.

Anybody know where/how to get Base Module repaired or exchanged? I hope it's not a throw-away item!
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  #22  
Old 11-28-2003, 11:07 PM
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Ed Hanna: Like many of the systems in your car, the instrument cluster has microprocessors on the circuit board. When the fuse that controls the circuit is pulled and re-inserted you are re-booting the circuit and the item will work OK for a while. I think that cleaning the fuses and fuse clips worked well on the 126 models, not the 140 models. I would hesitate to take the soldering iron to the circuit board if the problem is a defective microprocessor.

Napoleon: You need to replace the 2 watt bulb on the left side of your cluster to illuminate the fuel gauge. Someone has a repair for the illumination of the outside temp display. There is a small LED that can be soldered in with a tiny bulb from Radio ShackThe temp display is on a small rectangular circuit board that can be unplugged from the main instrument cluster circuit board.This is the board mentioned by Ed Hanna. I can access the instrument cluster wiring diagram on my Alldata subscription for my '93 300SD.. My '93 300SD has the soldered in bulb wheras my '95 S350 has a replaceable bulb.

The following post was from Benzworld forums:
http://www.benzworld.org/forums/messages.asp?messno=49782&id=10&view=t

Adjust the steering wheel to lowest position. Disconnnect the battery. As stated above, use the tools to gently nudge out the cluster. It's held in place by 5 pressure wedges. Remove 4 plugs on the back. There is no speedo cable to deal with. Take the cluster into the house and set it down on a clean towel to avoid scratches The temp LCD unit is on a plug in circuit board and comes out the front of the cluster. Remove ONLY 2 screws which hold the clear front assembly to the main unit. You'll see which ones when you have it in front of you. Pry at 5 plastic snaps to remove front. Grasp the LCD and gently pull forward; maybe wiggle a bit. The lamp is soldered into the circuit board. Use solder sucker and very low wattage iron to remove old bulb. It's a very delicate circuit board. Replace bulb with 60 ma wire lead bulb from Radio Shack ( 2 for $1.29 ) It's a bit smaller physically, but it will work just fine. Now put it all back together. About a 1 hour job. ( Not counting the trip to Radio Shack )
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  #23  
Old 11-03-2005, 01:59 PM
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got a problem

Okay well I got a pickle. None of the inside lights on my 400se are working. Well the dome lights work but the cluster nope, ac, nope, switches nope. I have been reading and I am going to try cleaning the fuses and see what that does. I read on another forum that I can try to replace the rheostat would that make sense to anyone?
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  #24  
Old 11-03-2005, 02:05 PM
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Quote:
Originally Posted by etrevino103186
Okay well I got a pickle. None of the inside lights on my 400se are working. Well the dome lights work but the cluster nope, ac, nope, switches nope. I have been reading and I am going to try cleaning the fuses and see what that does. I read on another forum that I can try to replace the rheostat would that make sense to anyone?
It would make even more sense to buy a test light so you can tell if your fuses and/or rheostat are actually at fault.

Yes, the rheostat is a common failure, but with a test light, you can know instead of guess.
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  #25  
Old 11-03-2005, 02:08 PM
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okay so buy a test light and check the fuses...and what else? go play by play if you don't mind i am so scared working on mercedes you do one thing wrong and you have to go to the stealership and they bend you over.
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  #26  
Old 11-03-2005, 03:56 PM
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Easy. If the fuses test good, pull the cluster and test for voltage at the rheostat connections (with the lights on, naturally). Use the Search function at the top of the page. All the information you need for checking fuses and pulling the cluster is there.
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  #27  
Old 11-04-2005, 12:14 AM
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okay so if i get voltage out of both of them would it correct to assume that is that rheostat and if so where can i get one of those
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  #28  
Old 11-04-2005, 10:51 AM
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MBZ Quality?

This thread reinforces my very low opinion of MBZ 'infamous' electrical system quality--almost as bad as that legendary 'Prince of Darkness--LUCAS in the 80's.

Most of MBZ 'technology for fuses and electrcail connections seems to have been firmly STUCK in the pre WW II phase of technology. Look at a early 90's Japanese or even US car and you find compact, no corrosion fuses, O-ring sealed water tight gold plated electrical connectors, etc. MBZ--cheap solder covered 1930's bayonet plugs, etc.
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  #29  
Old 11-04-2005, 11:42 AM
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we established that the electrical sucks now we are trying to fix things i used to drive an 87 420SEL that was the best car in the world. 350000 miles original engine and tranny, not to through the thread off topic anyone have any answers to my previous question?
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  #30  
Old 05-31-2007, 06:55 PM
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380SL odometer problem

I am about to purchase a 1982 MB380SL covertible, but at the moment it's in the garage for safety inspection and a repair on the odometer, which just apparently quit for no reason.
Mechanic states the unit is electronic, and is in a sealed unit with the speedometer. He states to get at it he would have to drill out the rivits that hold the unit together, but if he does that, the holes will be visible when the unit is reintalled in the dash. The speedometer works fine.
Does anyone know how to repair the odometer in this type of unit?
My apology if this is not the place to post this message. I find the whole posting thing a bit confusing.
JerryR in Amherst, Nova Scotia


Last edited by JerryR; 05-31-2007 at 06:57 PM. Reason: Not complete
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