Mercedes-Benz Forum banner

1 - 17 of 17 Posts

·
Registered
96 SL600, 07 BMW M5 ,04 545i sold, 2013 C300 Sport (for wifey) 03 CL55 s/Chg sold,91 500SL, sold
Joined
·
118 Posts
Discussion Starter #1
Hello Folks...I was wondering if anyone that currently or ever did own any mercedes w140 body or R129 series experienced the dreaded flashing instrument cluster lights or dead cluster issue.I know there has been numerous post on fixing the cluster by changing the 3 capacitors on the circuit board.I am aware of that and I did mine years ago, that fixed my temporary blackout/malfunction issue whenever I used my turn signal.My question is that recently I had an issue with my battery and alternator upon which I changed both.Just before changing them I started experiencing the flashing lights/dead cluster issue again.Only temperature gauge works.Does any one know what else was changed their cluster beside the capacitors? Something else such as a power regulator must need changing but which one?Any ideas?..Yes, I did try to change the capacitors again.But this time no luck? Secondly does anyone know or have the wiring diagram for the cluster.Mine is a 91'500sl but I think it will share certain common traits with it's siblings.Any help will be appreciated.Thx.
 

·
Registered
2006 S500 AMG Wifes Rig Hillbilly Girl 02 ML320
Joined
·
2,332 Posts
When mine went bad I got a used circuit board and plugged in my gauges and I was ready to go!!


Smokie
 

·
Registered
96 SL600, 07 BMW M5 ,04 545i sold, 2013 C300 Sport (for wifey) 03 CL55 s/Chg sold,91 500SL, sold
Joined
·
118 Posts
Discussion Starter #3
Thx for the quick response.How did you get the circuit board? Was it purchased from the dealer, service center or junk yard?..I actually have a used cluster that I purchased about 4years ago on ebay and has been working fine till now.There are service/repair center that claim they can fix the cluster when the flashing issue is not fixed by just changing the capacitors.I don't expect them to of course reveal their trade secrets,but I have done a lot of research and sources point me to a voltage regulator since our cluster apparently function on 6 volts.If the regulator fails it feeds a full 12 volts to the cluster which is not appropriate.This present the flashing issue.I am therefore trying to find out which regulator might be the culprit/s.
 

·
Premium Member
Joined
·
867 Posts
There are what appear to be 2 regulators on the rear-most board in the cluster. To get at them remove the 3 screws on the back of the cluster that allow the rear section to hinge open. Then remove the rear plastic shell by taking out the 4 screws (2 at each end) on the board attached to the shell. The regulators are at each end on heat sinks.
 

·
Premium Member
1999 S600 Sedan, 1999 S600 w/ 4-pl seating, 1995 S600 Coupe, 2-1992 600SEL's, 2002 ML55, 1998 SL600
Joined
·
2,425 Posts
BBA-Reman does a great job restoring electronics, and the best part is they give a life-time warranty on any work they do. Even if you bought the part new from MB, you'd only get a 1-year warranty, so BBA is the way to go. And they're located in MA, or at least their US repair facility is.
 

·
Registered
96 SL600, 07 BMW M5 ,04 545i sold, 2013 C300 Sport (for wifey) 03 CL55 s/Chg sold,91 500SL, sold
Joined
·
118 Posts
Discussion Starter #6
Thanks guys for the info.Tlampre,funny enough I had the cluster apart on my work bench and I kept looking at the two heat sinks that you described.I said to myself that they got to serve a major function here, with all that heat that needs to dissipate from the circuit board.I took a ride down to my local radioshack/electronic store.I picked up a few voltage regulators.They only had two versions available one labeled 7805 which is a 5V regulator and another 7812..which is a 12 volt regulator..but this on states variable? I think the labels on my originals referred to 8V regulators unless I am reading wrong..Therefore I am wondering if I can use a resistor of some sort of regulate the correct output required.Anyway I will try to change them and update you on my findings.Thx again :)
 

·
Registered
Joined
·
5 Posts
I too have changed all 3 capacitors and still have dash flash I'm currently thinking of going for the offer on eBay of repair for r129 analog clusters might be worth a look I did try a w140 cluster of the digital type but speedo doesnt seem to work with that option so I'm back to square one basicly you are not alone with this problem Hopefully someone will be able to shed some light here
 

·
Premium Member
Joined
·
867 Posts
One of my spare clusters has a part number starting with 129 instead of 140. It is analogue. I think the early clusters are interchangeable between W140/R129. With digital clusters it depends on whether or not it was a digital made to replace broken analogue, which should be OK, or for the later models, which will not work. That is what I have managed to figure from the posts here.

As for the regulator, I'd go with the original part. There should be a part number on it and any mail order electronics store will have them. But, if are in a hurry, you can get a data sheet for the original part. Make sure you solder the pins of the 7805 the same way (usually all the same) and you might get lucky. You won't damage anything by supplying too low a voltage.

I just did a search for a 7806 and they are all over the place and only cost a couple of bucks.
 

·
Premium Member
Joined
·
867 Posts
Just got home from work and checked my cluster. The part number is L4785CV which is a 5v regulator. The 7805 is straight swap.
 

·
Registered
92 500SEL to 01 E320T current 2014 lexus LS460
Joined
·
3,886 Posts
The 129 cluster will fi but all the readings will be wrong, celcius, kilometers, fuel level etc there were three variations of the 140 speedo
read the faq
MBCluster.com Mercedes W140 Instrument Cluster Repair Homepage
I have had mine repaired at Programma, and they replaced a voltage regulator and some capacitors, I had them do all the bulbs also. A new digital cluster is over $1200 and they wont program it to your mileage you will have to take it to a speedo shop and they might programm it, unless your odometer works they will put a sticker on it saying mileage incorrect.
 

·
Registered
96 SL600, 07 BMW M5 ,04 545i sold, 2013 C300 Sport (for wifey) 03 CL55 s/Chg sold,91 500SL, sold
Joined
·
118 Posts
Discussion Starter #11
Thx for the update Tlampre..I have the exact part # L4785 CV on one of the voltage regulators as described.The other regulator has a different part # which I had a problem with finding the right voltage.. I will double check the part number when I get home tonight.One thing I noticed is that this one has a small resistor sitting in front of it.I have a feeling it's due to a higher voltage rating.You are also correct Peter about the interchangeable cluster between 140/129..They are not that compatible.By the way do you have an idea or pics on what regulator was changed on yours.Thx again.
 

·
Premium Member
Joined
·
867 Posts
I didn't check both parts. Actually I got my daughter to read it as even with glasses on I couldn't see it properly. (So sad being old and decrepit). I'll have to get her to read the other part for me tonight.

As for being interchangeable, my experience differs to the MB Cluster FAQ. I have 3 clusters; from a 1991 300SEL, 1993 400SEL and a 1992 600SEL. The cluster in the 600SEL was the one with the 129 part number with dual range speedo and odometer in miles. I swapped with the 400SEL to get metric only. All have worked fine and I've noticed no difference in readings of any of the gauges and I used all of them for my interstate trips. Used the 300SEL one for a while but the odometer is broken. Never ran out of fuel and consumption calculations were the same.

I'm not saying any cluster you can buy on eBay will be guaranteed to work, but the blanket statement on the MB Cluster FAQ is not correct.
 

·
Premium Member
Joined
·
867 Posts
No, L4785 is 8.5 V. See data sheet
Absolutely right, my bad eyes again. L4705 is the 5v one. A 7809 (9v) should be OK if the original part is hard to get. Sorry.

The other chip is a Philips BUK-50B power transistor. Exact data sheets are hard to find but you can just buy one on eBay and replace it:
BUK453-50B POWER TO-220 STYLE PACKAGE NOS! BUK453 | eBay

Couldn't find a USA source for the L4785, but the UK has this:

1 PC. L4785CV Very Lowdrop Voltage Regulator L4785 8.5V | eBay

Only a few bucks all up and a bit of a wait for the postman.
 

·
Registered
96 SL600, 07 BMW M5 ,04 545i sold, 2013 C300 Sport (for wifey) 03 CL55 s/Chg sold,91 500SL, sold
Joined
·
118 Posts
Discussion Starter #15
Thx Myarmar for the update .I will try to find a replacement locally since Radio shack
only carries 5volts and an adjustable/variable 12volt version..Not sure how that will work.I will also try and order the two part #'s online if not found locally.I will keep you guys posted on further research. I really appreciate all the support team :)
 

·
Registered
92 500SEL to 01 E320T current 2014 lexus LS460
Joined
·
3,886 Posts
It was a stand up three pin affair, as i said I wanted a complete redo including bulbs and oodo bulb which is soldered in. I got two electrolytics the regulator, and all the bulbs in little bags. I got one day service since they are 40 miles away.
there were some posts on the subject check "Instrument cluster flashing", and "500SELwhy alllights come on" they were hot subjects in early 07
 

·
Registered
96 SL600, 07 BMW M5 ,04 545i sold, 2013 C300 Sport (for wifey) 03 CL55 s/Chg sold,91 500SL, sold
Joined
·
118 Posts
Discussion Starter #17
Well folks,I needed to update everyone on my findings.My R129 cluster as I stated was sent for repair.I got a call from the repair center that apparently my circuit board was damaged and beyond repair.The service center had another cluster which they sold me.I was glad to get another cluster but soon realized another issue.The cluster that the service center sold me had two issues 1) Erratic or jumpy speedometer and fuel gauge reading was wrong by about 1/4 tank more? I immediately suspected that this was probably for a W140 body or needed calibration? I sent it back to the service center and they checked it and found no faults.I even opened up the unit and found a R129 sticker on the circuit board but not sure why my speedometer was jumpy and wrong fuel reading.This actually caused me to run out of gas one night just 3 blocks from home..You can guess how frustrating I was! I then decided to either bite the bullet and order a new one from the dealer for $998 or try to find another used one online.I took the chance and picked up one online which now works perfectly.So to summarize the issue, my original cluster could have been repaired by just changing the three capacitors on the circuit board.If that does not fix your issue,then you most likely have a damaged circuit board like mine which may not be repairable.Hope this info helps someone.Good luck.Thanks to all the members that contributed to this thread.
 
1 - 17 of 17 Posts
Top