Help with w124 300d required.

[smoothcoupe]

Hi all , just got a 1992k pre facelift 300d with the normally aspirated engine, car is a project for next year, will be fully painting it addressing rust issues etc. the rev counter is not working and the wiper is on all the time at one speed all be it a little slow, had to remove fuse to stop it. Any ideas?? Haven’t checked the ovp relay as yet. Or can anyone recommend a good specialist who can sort a few bits whilst it is not being used. Thanks.

 

[Vin16]

For your 1992 pre-facelift 300D having issues with the non-functional rev counter and the wiper operating constantly at a single slow speed could stem from various causes. Here are some suggestions and steps you might consider:

1. Rev Counter Not Working:
   • Start by checking the connections to the rev counter itself. Ensure the wiring is intact, and there are no loose connections or damaged wires leading to the instrument cluster.
   • The issue might also lie within the instrument cluster or the sensor that provides the signal to the rev counter. Check for any corrosion or loose connections in these areas.
   • Verify the functionality of the rev counter itself. Sometimes, the internal components might fail, requiring either repair or replacement of the instrument cluster.
2. Constant Wiper Operation:
   • The continuous operation of the wipers at a single speed could indicate a problem with the wiper switch, the wiper motor, or the associated wiring.
   • Check the wiper switch for any signs of damage or corrosion. A faulty switch might cause the wipers to operate continuously.
   • Inspect the wiper motor and its connections. There could be a problem with the motor itself or the wiring leading to it, causing it to stay engaged even when turned off.
   • Since you've removed the fuse to stop the wiper, it's possible that the wiper relay or its circuitry might be malfunctioning. Consider checking the wiper relay for any issues or swapping it with a known working relay to test.

Regarding the OVP (Overvoltage Protection) relay, it's a good step to check this component as well. The OVP relay in some cases could affect various electrical systems in the car. If you suspect it might be contributing to these issues, testing or replacing the OVP relay could be beneficial.

 

[smoothcoupe]

For your 1992 pre-facelift 300D having issues with the non-functional rev counter and the wiper operating constantly at a single slow speed could stem from various causes. Here are some suggestions and steps you might consider:

1. Rev Counter Not Working:
   • Start by checking the connections to the rev counter itself. Ensure the wiring is intact, and there are no loose connections or damaged wires leading to the instrument cluster.
   • The issue might also lie within the instrument cluster or the sensor that provides the signal to the rev counter. Check for any corrosion or loose connections in these areas.
   • Verify the functionality of the rev counter itself. Sometimes, the internal components might fail, requiring either repair or replacement of the instrument cluster.
2. Constant Wiper Operation:
   • The continuous operation of the wipers at a single speed could indicate a problem with the wiper switch, the wiper motor, or the associated wiring.
   • Check the wiper switch for any signs of damage or corrosion. A faulty switch might cause the wipers to operate continuously.
   • Inspect the wiper motor and its connections. There could be a problem with the motor itself or the wiring leading to it, causing it to stay engaged even when turned off.
   • Since you've removed the fuse to stop the wiper, it's possible that the wiper relay or its circuitry might be malfunctioning. Consider checking the wiper relay for any issues or swapping it with a known working relay to test.

Regarding the OVP (Overvoltage Protection) relay, it's a good step to check this component as well. The OVP relay in some cases could affect various electrical systems in the car. If you suspect it might be contributing to these issues, testing or replacing the OVP relay could be beneficial.

Thank you for the pointers.

 

[ChipChop]

Replacing all the continental fuses for new is a good starting point for troubleshooting electrical issues on these old 'analogue' cars. The only time i had a non functioning rev counter on my diesel w201 was fixed by resoldering dry joints in the OVP relay. Quite fiddly to take apart but once prised open a very easy fix. Just touch any obviously cracked solder joints with a hot soldering iron and hopefully job done. Reseal the OVP relay using a silicone sealant. There is also a fuse on the top of the OVP relay itself to check.

 

[smoothcoupe]

Replacing all the continental fuses for new is a good starting point for troubleshooting electrical issues on these old 'analogue' cars. The only time i had a non functioning rev counter on my diesel w201 was fixed by resoldering dry joints in the OVP relay. Quite fiddly to take apart but once prised open a very easy fix. Just touch any obviously cracked solder joints with a hot soldering iron and hopefully job done. Reseal the OVP relay using a silicone sealant. There is also a fuse on the top of the OVP relay itself to check.

Thank you will check

 

[DITTRICH]

Monowipers are not a service item and they can get gummed up with crud, eventually causing the mechanism to fail. Clearly there is the on all the time issue but the mechanism will need a good oil and clean in order to prolong it's life. You need to investigate how to get the shroud off the wiper to clean and degreaser the monowiper. I kept my w202 monowiper and my w124 monowiper going for years with simple cleaning and regreasing. Vaseline!!!

 

[optimusprime]

You need this smooth Model 124 Maintenance Manual Index its free we all use it that own W124s

 

[Smiley]

Your wiper problem is likely to be either a fault with the wiper stalk or (more likely) a relay under the bonnet. Not the OVP relay but a wipers/indicators relay located in the relay/fuses box at the rear of the engine bay on the offside (RHD) of the car. Try wiggling the relay in its holder - these relays were troublesome when the cars were new. Dry joints is the root cause of the problem.