Instrument Panel Questions - PeachParts Mercedes-Benz Forum

amt230 · #1 03-10-2011, 04:10 PM

Hi All - well, I'm trying my best to take everyone's advise and start learning to repair the car. Since the car is just back from the mechanic, there's nothing under the hood in need of attention (for now), but immediately after getting it home I pulled the instrument cluster and popped out all my non-working items. So, some questions related to each:

Clock - I'm not even going to bother getting into this one, unless people have had luck squirting lube on it randomly? Anyone have a recommendation of anywhere I could send/bring to have it rehabbed? Also, I'm missing one of the two nuts that keep it on, if anyone has one lying around...

Rheostat - Unfortunately, as suspected the coil is totally mangled, making this detailed fix (Refurbing the Dash Light Rheostat (Caution: For The Purists Out There)) not an option. Although I know I'm going to get a crowd of "just jump it" responses, I'm thinking of replacing (this way I can actually avoid pulling the dash pod all the way out to solder at bench - I couldn't figure out how to disconnect the indicator and temp cables). Anyone buy one recently?

Odometer - I took a break from this post to try my hand at it, and it looks like it worked! This 8 year old thread is still going strong! Odometer problem- 1972 250

Lastly, since I fixed the odometer, I'll pop that back in, but just want to confirm my suspicion that there's no problem driving around with a few blanks in the dash (the clock and rheostat).

Next up after this, fixing the reserve tank light, although I suspect that has less to do with the dash and more to do with the signaler being all cruddy.

Thanks all!

Yak · #2 03-10-2011, 05:48 PM

Actually that rheostat looks salvageable, at least as a single setting fix until you could get a replacement. Look at the bottom pic in post 4 of the rheostat thread. What happens is the electricity comes in from the corroded spot in the lower right then travels through the resistance-wire spring then across the armature in the top pic. Then it goes through the spot in the center and out the other side.

If your spring/coil is intact and electrically connected to the case but simply out of place you can follow the disassembly and cleaning instructions. Reassemble it with the armature rotated to the full bright position (fully clockwise, like a volume knob) and leave it there. The condition of the spring would probably mean it'll pop back out if you tried to adjust the brightness but full bright is probably what you want anyway.

meltedpanda · #3 03-11-2011, 02:52 PM

if your clock is self winding type then it can be serviced , but ever so carefully, search my name for clock repair. Do not lube it , that will only kill it.
Missing dash componenets will not hurt anything. I am with YAK, that rheostat looks good , try your hand at repair.
Your reserve light is linked to the fuel sender in your tank. Once again fixable, but often by replacement over cleaning , but some can be cleaned. Once again search my name for fuel sender repair ( seeing a pattern here) I cut my teeth on the W114/5's and W123 and 126 , now solid into W107's
Have fun, enjoy the ride ( literally ) !

amt230 · #4 03-11-2011, 05:06 PM

Thanks! I'm worried about trying to rehab this rheostat because the wire is so mangled that if it was moved it would undoubtedly fail again, and this is how I got here in the first place an inquisitive friend who I allowed to drive the car asked and immediately started turning it upon hearing the answer. I hate to have the response to any excited question about the car start with "stop, don't touch that."

Can anyone say either way if the rheostat from a '72 280se 4.5 would work in my '70 220d?

meltedpanda · #5 03-11-2011, 08:40 PM

it should

amt230 · #6 03-12-2011, 12:32 AM

Thanks. So, I got into the clock, and did in fact find that the internal fuse had been triggered. However, I'm thinking that there might be more of a problem...

Even with the fuse blown and the clock not getting any power, it should theoretically tick if I manually rewind the disc, right? However, it doesn't do so unless I assist the disc in putting more pressure on it so that the gears get in motion. The movement seems fine though - if I assist, it ticks nicely. I'm just not sure whey the disc does not apply enough pressure to run the clock when wound. The clock appears clean and in good condition, so I can't figure out how to get this thing to run!

meltedpanda · #7 03-12-2011, 09:51 AM

once it is energized it should wind and then even without power should tick, you may have more of an issue as you suspect. Tough to say without looking at it , keep playing around, you have nothing to loose

IVIuzzy · #8 03-12-2011, 10:51 PM

I have a clock and a few rheostats let me know if u want them, u can have en free just tell me address

amt230 · #9 04-10-2011, 06:26 PM

So, you all were right, and the rheostat was, in fact, salvageable. And, after fumbling with the odo, it's been running well for about 100 miles.

The mechanics on the clock are running well after some oiling, but I still need to figure out how to get my hands on some low temp solder to close the circuit. Does any one have any leads for fusible solder (or any extra from their clock rehab)?

Thanks!

meltedpanda · #10 04-10-2011, 06:34 PM

man , we love it when we are right

lol

280EZRider · #11 04-22-2011, 03:10 PM

I understand your not wanting to jump the rheostat - kind of a bastardization of MB - but the fact is even with a new one, you´ll still have to keep it completely open. There just isn´t much light supplied the the cluster, so in the end, it won´t make any difference if you jump the original rheostat or install a new one.

carnut · #12 04-28-2011, 03:18 AM

I've owned several 60's to 70's Mercedes and I've soldered a jumper wire on the back of the rheostat on every one of them. Its free and the dash lights work every time. A 108 chassis rheostat appears to be the same. I just got a 73 280c last week and removed the 2 screws holding the rheostat to the cluster with it dangling on the steering column. I placed the rheostat on an open vise and soldered on a wire. I just used a very short screwdriver to remove and reinstall it. You have to gently rotate the black knob on the cluster face as you reinstall it, the shaft has a flat that must re engage the knob.

mgburg · #13 04-28-2011, 03:30 AM

What's the "full-circuit" resistance on that rheostat? 50-ohms? 100-ohms? 2k-ohms?

I'm thinking about 2nd-sourcing the bugger if I can find a properly-sized/wattage rheostat.

$128.00 for one just seems to be a bit too steep for me on such a small component.

My '76 & '77 both need 'em. So now, I'm looking at about $256.00. Doesn't make too much sense, does it?

Right now, on the '76, I'm using a few of those "blue LED" stickons...not too distruptive but you need to use the lighter-socket to light-em up. That looks a bit chincy. I'd like to get some of the "fine-wires" out of the way...

meltedpanda · #14 04-28-2011, 11:01 AM

well it runs very small bulbs, but really , jumpering is the way to go

amt230 · #15 02-17-2013, 10:27 AM

So, years later, I'm still working my way through the instrument panel. The refurbished rheostat is back in and works well, although as noted, you end up leaving it cranked up all the way all the time. Odometer still running strong after a couple thousand miles.

The clock is intermittent, may have issues with getting enough power to rewind it when the car is off, but still testing.

As for the fuel sender, after pulling and cleaning carefully, it works well, except that the reserve light is on all the time. If the float is up and reading correctly, the copper contacts are clearly not touching, so how is that circuit closed to light the reserve light? I guess I can't conceptually understand how the reserve light works, and how it could remain on constantly if there is no contact in the fuel sending unit. Any thoughts?

Thanks!