W115 Instrument Cluster Questions

[Doskiez]

Hello all,
I have looked around for a few of these topics but haven't really found the answers I need. To start with I have a 1976 300D, auto trans. I purchased it at auction so I really don't have any history on it. I am slowly going through it and restoring a system at a time and I am trying to prepare for fixing my instrument cluster issues below:

1. The previous owner removed all back light blubs from the dash for some reason, is there any logical reason to do this, or would some other issue necessitate this?
2. The oil pressure gauge is stuck at max pressure and never moves, even when the engine is off. Is it possible to take them apart and repair them, or should a replacement be located.
3. My temperature gauge reads normally most of the time but occasionally, while driving, it will max out. The car does not act like it is overheating and the motor does not seem any hotter than normal so I suspect either a faulty sending unit or a chaffed wire somewhere. Are there any known issues that could cause that.
4. The clock does not work. Not a huge issue but I would like to get it working if possible. It is a quartz movement. Is there a modern replacement movement that can be used in place of the factory one if it is not repairable?
Thanks in advance everyone.

[meltedpanda]

cant think of a reason for no bulbs, and it sounds as though you have some bad gauges, If I were you rather than trying to work out the electrical , gauge gremlins , Id source a new old used dash pod, easy to take out and replace

[gmog220d]

Kinda sounds like someone got a little crazy with that instrument cluster. I've attached a couple pics below that show some oil gauge and instrument cluster lighting details related to my reply.

Originally Posted by Doskiez

1. The previous owner removed all back light blubs from the dash for some reason, is there any logical reason to do this, or would some other issue necessitate this?

Did they simply remove the bulbs from the cluster and put the holders back? Do you need bulb holders? The bulbs are 12V 3W. Don't know what to think about why all yours are gone.

Originally Posted by Doskiez

2. The oil pressure gauge is stuck at max pressure and never moves, even when the engine is off. Is it possible to take them apart and repair them, or should a replacement be located.

Not sure if this is serviceable. It's a basic mechanical gauge using a Bourdon Tube, and the core assembly is riveted and soldered together. The tube flexes with pressure, and the free end is connected to linkages that transfer the movement to the needle via a rack and pinion. A pegged needle in the absence of pressure would indicate a mechanical problem with the gauge. Bent Bourdon Tube? Rack and pinion slipped teeth? Needle clocked incorrectly? Something else? I'm not sure you could fix it and have a calibrated gauge afterwards, but it's certainly worth digging it out of the cluster and taking a look at what you've got.

Originally Posted by Doskiez

3. My temperature gauge reads normally most of the time but occasionally, while driving, it will max out. The car does not act like it is overheating and the motor does not seem any hotter than normal so I suspect either a faulty sending unit or a chaffed wire somewhere. Are there any known issues that could cause that.

M-B used two types of temp gauges in W114/W115s that I've seen. My '74 has an electric type using a typical sensor with a wire running to the gauge. My '73 had a mechanical "capillary tube" type in it. By your description it sounds like you have the electric type and a possible wiring problem between the sending unit and the gauge. Assuming the needle pegs when the wire that attaches to the sending unit is touched straight to ground it sounds like you've got a short somewhere.

Originally Posted by Doskiez

4. The clock does not work. Not a huge issue but I would like to get it working if possible. It is a quartz movement. Is there a modern replacement movement that can be used in place of the factory one if it is not repairable?
Thanks in advance everyone.

The problem with these clocks is getting to the movement. They are crimped shut and you'd stand a very good chance of ruining the chrome bezel in the process of prying it off. I've got one I wanted to take apart and service but I was not able to figure a way in that didn't involve use of destructive prying and bending forces applied by tools not meant for the job, so I stopped there. If one could get into it I'm fairly certain the innards are serviceable. Does your clock make sounds when connected to power, even if the hands don't move? Probably as simple as gummed up ancient oils.

*************

If you end up needing a oil pressure gauge or cluster bulb holders send me a PM. I'd love to move some of the "treasure" stash to someone who actually needs it! But Ron's idea of sourcing a complete, working cluster is also a good one in that it could save you time and headache factor - just plug it in and go!

[Idle]

Give up on the oil pressure gauge. It is just worn out. Replacement is the only option. But the good news is that entire clusters are not expensive on the bay.

There was a time when removing the bulbs and painting them orange was a thing. It gave you a better glow and was an attempt to ape the BMW lighting. I am only guessing here but the POS likely had a reason to remove the bulbs but then needed the car so he dropped n the gauge cluster and never finished his project.

The clocks are easy to repair IF YOU HAVE THE RIGHT EQUIPMENT. Just look into Hemmings under services and check out clock repair. Hollywood Speedometer has been reaping these VDO clocks since forever and can make it work like it should.

In other words: The cost for clock repair is not backbreaking.

[meltedpanda]

PM me , I have a guy that will repair your clock with a lifetime guarantee

[Doskiez]

I appreciate the responses everyone. Sounds like a new (to me) cluster might be a good place to start. If I can pull the one I have apart and fix it, that would be ideal. Otherwise I can get a new one, send it off to have the clock fixed if necessary, and still drive the car with the original installed. As far as the blubs go, I think most of them are rolling around in the glove box.
After the cluster is sorted just have the vacuum locks to sort out and a few small oil leaks to fix and it will be back to factory performance.

[meltedpanda]

if you pull the cluster you may see some of the bulb traces broken or corroded , those can be jumpered with a wire , the dim bright knob can also be bypassed , those are normally bad with corrosion

[Idle]

Originally Posted by Doskiez

I appreciate the responses everyone. Sounds like a new (to me) cluster might be a good place to start. If I can pull the one I have apart and fix it, that would be ideal. Otherwise I can get a new one, send it off to have the clock fixed if necessary, and still drive the car with the original installed. As far as the blubs go, I think most of them are rolling around in the glove box.
After the cluster is sorted just have the vacuum locks to sort out and a few small oil leaks to fix and it will be back to factory performance.

A lot of times the only problem with the door locks is one rubber diaphragm has a hole in it. This messes up the entire system.

The rubber parts can be replaced if you can find the parts. I think the official line is they are not rebuildable but they are. Just work with them some and you will find how they come apart.

Go slowly at first. These are rather tricky to figure out the first time you tear into them. After that you will find they are no big deal.