WolfieBase Posted April 5 Share Posted April 5 Good evening everyone... Progress is being made gradually, but a new challenge has arisen. When I purchased the automobile, the previous owner had tampered with several of the ground cables under the dashboard. He was unable to recall the reason. I had around three components that were visible, indicating that none of the indicators on the automobile were functioning. Since I am not knowledgeable about electrical systems, I hired an individual who successfully restored the functionality of the electrics by reestablishing the connections. Everything was satisfactory, with all indicators functioning properly. While preparing for the Ministry of Transport (MOT) test, I activated the side lights, causing the two green indicator lights to illuminate with a dull intensity. I have tested the indicators and they continue to function well, albeit they now provide a visually impressive display. I am experiencing a complete absence of dashboard illumination. Consulted with an electrician who believes that the issue may be related to a grounding fault or maybe inside the wiring of the instrument panel. I have acquired a substitute as a precautionary measure. Additionally, I have seen an exposed black/red wire at that location, the purpose of which I am uncertain. The electrician's assistance was not very helpful, to be honest, which is disappointing considering the amount he cost me! I have included a YouTube video that shows everything except for the part when I use the rheostat. Quote Link to comment Share on other sites More sharing options...
WolfieBase Posted April 5 Author Share Posted April 5 The car in question is a 1985 W123 300TD. Any assistance would be much appreciated. Quote Link to comment Share on other sites More sharing options...
WolfieBase Posted April 5 Author Share Posted April 5 Quote Link to comment Share on other sites More sharing options...
Black_raven Posted April 5 Share Posted April 5 It seems that some tinkering has taken place. Most likely an effort to rectify a prior malfunction by using a feed or employing a remote earth instead of addressing the initial issue directly. The side lights seem to be searching for a ground connection via the indication warning bulbs. If both bulbs illuminate, it might indicate that the danger light circuit is affected. Perhaps inspect the non-original wiring to determine its path and the circuits it impacts. As previously said, it seems that a seemingly minor failure has escalated into a more complex series of problems. Quote Link to comment Share on other sites More sharing options...
BENZE220AMG Posted April 5 Share Posted April 5 I agree with Black_raven assessment that there is likely an earth fault. Have you inspected the electrical connections at the tail lights? The likely cause of the problem is inside your cluster and switch, since the issue is consistent on both sides. I would remove that group of objects and begin the process of following the wires back to their source. Upon discovering someone's actions, it is possible to reverse them and return to a favourable initial state. I am acquainted with a skilled automotive electrician who operates in the Dartford/south London area. Therefore, whether or not he can assist you will depend on the location of your vehicle.  Quote Link to comment Share on other sites More sharing options...
WolfieBase Posted April 5 Author Share Posted April 5 Thank you both. Yes, there were exposed brown ground lines below. I am curious whether the previous owner had this issue and it has already been resolved. Meanwhile, I have purchased an additional cluster from Rob P as a backup in case the circuit board is the cause of the malfunction. I really dislike electrical devices. Quote Link to comment Share on other sites More sharing options...
BENZE220AMG Posted April 5 Share Posted April 5 I am sceptical that it will be the cluster mate. The defect does not seem to be of that kind to me, and there will be little circuitry for the indication tell tales in a vehicle of this age. It seems that you have some exposed wires resulting from earlier improper handling. You should investigate and determine their respective destinations. The peculiar brownish-red striped object located above the throttle catches my attention due to its unconventional hue, which is not often seen in aftermarket products. I am curious to understand the purpose or significance of this component. Curiously, have you seen the tail lights during these occurrences? If the indicators are not illuminating while the lights are on, even if just to a little extent, it may be necessary to remove the lens in order to fully inspect the bulb. Typically, this issue is indicated by the presence of additional electrical current flowing through the brake lights due to a faulty grounding connection. However, it is advisable to verify this possibility, since it requires no financial investment. Please provide regular updates since I am really interested in the final result. Quote Link to comment Share on other sites More sharing options...
WolfieBase Posted April 5 Author Share Posted April 5 Â @BENZE220AMG Thank you. I have been informed that there is a possibility of circuit board failure, thus I have obtained an additional one as a contingency measure. The cable you mentioned, which seems brown or red, is really black and red. I have not yet followed its path, but according to the schematics, it is connected to the tail lights. Tomorrow, I will inspect the tail lights, which function well when the lights are off but have not been tested with them on. Quote Link to comment Share on other sites More sharing options...
WolfieBase Posted April 5 Author Share Posted April 5 It is worth mentioning that this vehicle previously had an aftermarket alarm installed, which was uninstalled prior to my ownership. Quote Link to comment Share on other sites More sharing options...
Ken_Lion Posted April 5 Share Posted April 5 The colour black-red most likely indicates a malfunction in the brake light. The left-hand side tail lights will be coloured in shades of grey or black. Grey/red, often known as RHS (Right Hand Side), Quote Link to comment Share on other sites More sharing options...
SD1too Posted April 5 Share Posted April 5 https://carmanualsclub.com/mercedes-benz-w123-service-repair-manual/ Quote Link to comment Share on other sites More sharing options...
SD1too Posted April 5 Share Posted April 5 http://www.peachparts.com/shopforum/diesel-discussion/401911-w123-instrument-cluster-lights-not-working-isnt-rheostat.html Quote Link to comment Share on other sites More sharing options...
SD1too Posted April 5 Share Posted April 5 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.