Gauges Stop working from time to time

[thysonsacclaim]

So I was working on the '74 450SEL a bit today. Changing the transmission fluid, tweaking the idle speed a bit and what not. I let her idle for about 45 minutes earlier as I am trying to burn most of the gas that is in there. As I noted in another thread, this car sat for about a year without being run in a very wet and humid environment. I want to make sure it has as much of the possible water in the tank removed. Don't really wanna drive it too much until I am sure I won't get stuck somewhere!

Anyway, I noticed a pattern with the gauges. When I drove this home from Orlando, FL to DeLand, FL, the gauges and turn signals had stopped working. They either went all the way up or all the way down, depending on the gauges. It was running quite warm at that time, as it needed a bit of water added to the radiator, which I did ASAP.

Then today, whilst letting her idle those 45 minutes, the gauges again acted up and stopped working. I noticed the first time this happened that they began to work again after I let her sit for a bit. I'm doing the same thing at the moment. Just letting her cool down.

But I have a theory about this. I think the heat under the engine compartment may be fouling the relays or whatever other electronics control the gauges. Twice it has happened. Twice it has been while the car was warmed up for a bit. It could be a short, but the circumstances are odd. The fuses are all fine. They could use replacing and the contacts are a bit tarnished, but they should still conduct, if at all minimally.

Does that sound plausible to you guys?

[thysonsacclaim]

It happened again. I drove it around the block, flicked the turn signals and noticed that the gauges went awry. I messed with the signals earlier in the day whilst it was not running so I could check all the bulbs and it did not happen then.

It seems to occur when the signal lights are turned on after the engine has been running for a bit. I checked it again later and they were working in a somewhat normal fashion, but the signal lights didn't come on. That is, the cabin indicator light flashed, but the actual outside bulb did not. I checked the bulbs so I know they are all fine. They did not appear to have shorts near the outlets, either. Also, the hazard lights work.

I'm going to try switching around the relays tomorrow and see if the condition improves. I don't have much experience working on mechanics, but I do have quite a bit of experience in electronics and fixing relays, wiring diagrams, soldering capacitors and transistors, etc. Perhaps it needs new relays. I'll swap them around and check the insides of them tomorrow. I may have something compatible that I can use temporarily to diagnose the problem. I have a garage full of resistors, wires, relays, transistors, photo eyes and whatever else you could need for electronics.

If only it wasn't dark outside--I'd be out there now!

[thysonsacclaim]

Gah! It appears this isn't my only problem.

The car started 'smoking' while I was running it. Popped the hood only to see white foam on one of the hose that leads to the AC receiver drier/accumulator. Going to have to replace that and recharge the system. It's unfortunate that R12 costs so much. I'll probably just convert i over to 134A.

As for the gauges they don't work at all now. I believe it must be a short. Apparently, the car has more electrical issues than I though. It appears that the fuse box has been replaced, although the box looks to be the correct type.

However, the push button at the end of the turn signal switch on the steering column, which is supposed to wash the windows.... Turns on all 4 head lights. I really do wish people who don't know diddly about electronics wouldn't try to hodge podge things together without checking it out. It looks like I'm going to have to check ALL the wiring now.

[thysonsacclaim]

We are having quite a deluge here as it is hurricane season, so I had to stop working on the car. It seems lie a lot of the electronics under the hood have been modified and/or disconnected.

1: It has the remnants of an alarm system. By the looks of the siren, it is not very old as the plastic is still quite shiny and it is obviously a fairly recent (5-10 years) looking model.

2: It had two batteries installed along with a battery isolator. I am working on removing this, but it's a cobbled up mess. Lots of electrical tape and ghetto piggy backs. Someone had no skill at all...

3: When I turn the lights on to the first head light position, two lights come on. When I switch to brights, again... just those two lights are on. I thought all 4 should come on when I switch it to brights. The wires on both sets of headlamps have been modified. There are cut wires just hanging about. However, the second set of head lamps (brights) is wired in... somehow... to the washer fluid dispenser switch on the column. Pushing this is, as if to wash the windshield, actually toggles the brights on, but they turn off when you let off the button.

4: There are places for wires to be connected to where nothing is plugged in and I can't find what goes there. One place is on the intake of the air filter cover, must be some kind of sensor. The other place is on the AC receiver drier. The are two outlets. the one on top is plugged in to the fan and the other has nothing plugged in to it.


For some reason, I think this car was once owned by some ghetto crack dealer. The tinted windows, ghetto alarm system, and shiny rims give it away.

I am going to post pictures of the wiring issues when I can. I have the wiring diagram, but it will take me a bit to familiarize myself with what the hell has been changed between it and the actual car. Perhaps if some of you have similar 450SELs, you might be able to direct me to pictures of what these things should look like or where I can find info. I am researching the library exhaustively atm.

Thanks!

Air Filter Intake:




AC receiver drier:

[KenM]

Hey man, sounds like you have your hands full with that wiring there, hours of fun in store by the sounds of it. Looking at your pics the paint job was a bit slap happy, sprayed all over the air con drier etc. It's a bugger if the air con is still on R12, I'd be surprised if you can even buy it, certainly it's illegal here in Oz to regas a system with R12, I know things can be a bit more liberal there. All the info on your wiring should be in the library, stick with it I'm sure you'll come up with a solution.

Cheers,

Ken

[oscar]

For some reason, I think this car was once owned by some ghetto crack dealer. The tinted windows, ghetto alarm system, and shiny rims give it away.

First thing I'd do is lift the carpets and remove the lower rear bench seat to look for cash, or crack   Hell, even in an ex family w116 I scored $8 whilst dismantling Good times!

As for the gauges they don't work at all now. I believe it must be a short.

That was my first thought with their intermittent behaviour.  You'll most likely find it's on the back of the cluster.  to remove cluster it simply just pulls out.  The earth works between the three gauge clusters by contact between solder points and cluster housings and if the screws clamping the each set of gauges is loose or can't be tightened you'll get this intermittent behaviour.  It happened to me once but only involved the tacho and was remedied via sodlerng a bypass wire.  The earth comes in to the back of the water temp/oil pressure/fuel tripple combo gauge via the multipin connector.  Here's some old pics what to expect http://forum.w116.org/mechanicals/faulty-tachometer/msg6922/#msg6922

However, the push button at the end of the turn signal switch on the steering column, which is supposed to wash the windows.... Turns on all 4 head lights.

This is can be a common issue because of two versions of the combination switch.  You'll find us talk a lot about early versus late and more often than not refers to pre1976 and 1976 onwards.  The periods signify a change of FI mainly but many other smaller items including the combo switch on the column.  The switch you have is probably this one below which is later style, but the one you should have is the second one for pre 76 cars.  They've got the same plug but note the different stick ends, especially the rocker switch in the second pic.  This is the one you need.  The manual shows how it's supposed to work in the third photo in conjunction with the rotary light switch on the dash.

[thysonsacclaim]

Thanks a lot for the help Oscar!

I will be checking out the cluster tomorrow; I need to fix the odometer anyway. Hoping the lock-tite trick will be all it needs.

I checked out the turn signal switches online. My are they expensive. It will have to wait, unfortunately. I need to ensure the engine is in proper running order first. What I do like about the MB electronics is that most things seem to be plug and play. No wire splicing necessary.

Brings me to another point. The tail light assembly on the passenger's side (it's LHD) that is accessible from the trunk to change the bulbs seems to not match the one on the other side. They are slightly different. I noticed the rear lights on both sides don't seem to light up at the same time on the same setting. Probably another pre-76/post-76 issue. I'll have to check it out. I hope it's not another $170-$239 part like the turn signal assembly.

Maybe I can find someone who needs my turn signal switch and we can trade. Haha.

[oscar]

Don't worry, no need to fork out big bucks for a new one. The reason those turn signals sticks get swapped out is because the early types have an all metal return mechanism which slightly wear out thereby stopping the signals from staying on.  I suppose people mistakenly put a newer type in that has a plastic return mechanism and aftermarket copies are about $80 compared to the $200+ for new original early types.   What I'd do is check out a wreckers place or ebay and buy a used one for very few $.  If that used one has a faulty return mech then there's an easy no cost fix option whereby you reprofile part of the mechanism with a small hobby file or rotary tool like a Dremel to make it work again.  Here's a link  http://forum.w116.org/mechanicals/tip-how-to-fix-turn-signalindicator-switch-that-keeps-returning-to-centre-off/msg3516/

Regarding a few other issues you've mentioned in this and the other thread.
- Speedo and Odo.  These are purely mechanical so if there's an earth issue to the instrument cluster or within the cluster, they should work regardless.  They both work off the speedo cable coming from the rear of the transmission so if the odo and speedo don't work, this cable must be either broken or disconnected.  A further common problem is for the speedo to work but not the odo whereby a metal cog looses grip on a shaft that holds the odo's numbered cogs.  It's a fiddly fix but I'd check the cable's integrity and connections first if possible.
- Back to the intermittent working gauges, I meant to add before that on the earth/grounding issue that after reading through about the custom wiring someone applied, it might just be the supply to the cluster but I'm not sure where that wire comes from before going to the multipin connector.  You sound like you've got more than enough skill to track that though.
- Electrical connection on the air filter housing.  This is the air temperature sensor and has the least effect on the operation of d-jet injection so far as the engine will still run.  However, it does have an affect.  I can't remember off the top of my head under what conditions it comes into play, like comparing various ambient air temps and engine temps, but I've noticed it does help control idle revs at different times when you run the engine with and without the sensor connected. It affects fueling whilst driving too but I can't say I've noticed any real difference or gains between it being connected and not.  But anyway, hopefully this wire and connection is still there.  Take the air filter housing off and look around near the number 1 cylinder's fuel injector.  Amongst the wiring there's hopefully a rogue wire and socket that's been folded back out of the way.  That's where it comes out of the wiring harness and it's where my sensor wire was tucked away when I first got my 350.

Regarding tail lights, I'm not sure what the difference is there.  When you get a chance post a pic or two of the differences you noted and I'm sure someone will be able to explain what's going on.  It might have to do with fog light or parking light activation whereby the LHS light on a LHD car might have an extra fitting but I'm just guessing. 

[thysonsacclaim]

First:
Thanks again for the insight! These are mostly minor issues and most things seem to be intact. It's dark here now (11:50 pm), so it will have to wait until tomorrow (unfortunately!).

This is my first Benz and first non-Japanese import car, so I'm definitely not in my zone. It comes with time, I suppose.

About the speedo/odo, I wasn't sure if they were independent of one another or not. Thanks for that info. I've done some speedometer cables before, so hopefully it shouldn't be a problem.

One question about the speedo cable:
Is there are gear at the base of it which connects to the tranny? All the speedos I have worked on simply consisted of the outer housing and a center plastic piece which was square in shape. This plastic piece spun inside the housing and inserted into a square slot in the transmission. That was with newer Japanese cars, though. I was told this may have a gear at the base, but the person who told me this (brother) wasn't sure. He has never owned a w116, just knew a couple people who had them.

Turn signal component:
So this erratic behavior of the lights is because of the signal switch? I will check out places online and the wreckers. My neighbor works at a local wrecker, but said they don't get many Benz of my era in. Those that do come in are often quickly scrapped and crushed. =/


I'm leery of this car because of the cost of some of the parts. I've never paid more than $10-18 for a relay and I see the OEM replacement for these run around $50-60. But oh how I love her more and more...

One final note: the correct behavior of the headlamps is that only 2 should come on when the light switch is turned all the way over? The brights, pushed on the turn signal switched, would then turn all 4 lights on, I assume.

Tail lights:
I'm going to post some more pictures online of the various issues I have. I have been reading the manuals, but it's hard sometimes to determine where a problem is if some of the parts have been swapped out.

Again, thanks for your help. It is greatly appreciated. The learning curve is steep in some aspects, but I should catch up soon.

[oscar]

I meant to get a quick response off before you hit the sack but 11:50pm is still way early in w116 forum time.

One question about the speedo cable:
Is there are gear at the base of it which connects to the tranny? All the speedos I have worked on simply consisted of the outer housing and a center plastic piece which was square in shape. This plastic piece spun inside the housing and inserted into a square slot in the transmission. That was with newer Japanese cars, though. I was told this may have a gear at the base, but the person who told me this (brother) wasn't sure. He has never owned a w116, just knew a couple people who had them.

No gear.  There's a clamp that attaches the outer sheath to the tranny and the cable froms into a tounge which slots into the gear that drives it.  I'd show a pic but can't find an old broken cable I had floating about.  Below is the transmission side of things. Top of pic is towards the front of the trans.  You can just see inside the clamp what the female side of the connection looks like.

Turn signal component:
So this erratic behavior of the lights is because of the signal switch? I will check out places online and the wreckers. My neighbor works at a local wrecker, but said they don't get many Benz of my era in. Those that do come in are often quickly scrapped and crushed. =/

One final note: the correct behavior of the headlamps is that only 2 should come on when the light switch is turned all the way over? The brights, pushed on the turn signal switched, would then turn all 4 lights on, I assume.

On the turn signal component question, I hope I haven't missed anything regarding erratic behaviour but yes, I would assume that a proper combination switch/stick would correct the turn signal and high beam switching. 
Note also that there'll be no washer function on the proper stick.  Down on the floor where your left foot rests there's a metal foot operated switch. Depressing that will see your washers jet water at your windshield and the wipers will operate.  When you take your foot off the switch, the washers stop but the wipers do an extra three wipes before turning off.

On the headlights, I'd rather a US w116er explain the proper function of the headlights.  The US headlights have two sealed beams each side whereas the rest of the world referred to as "euro" headlights are different as below.  I'm not sure how the US headlights are supposed to work sorry, but one thing to mention is to turn the rotary switch all the way then pull it towards you.  On euro lights it makes the outer marker/fog lights come on.  That may be how you guys get the outer sealed beam to work.  Don't be alarmed if the rotary switch cap comes off.  They do that since they loose grip a little. Just push it back on if that happens.

[thysonsacclaim]

I pulled out the cluster a bit and the gauges began working again. You were spot on! I will pull it out entirely tomorrow and check all the connections.

Edit:

Rotary switch -
Unfortunate thing about pulling the rotary switch out is that it does nothing. I am nearly sure this is a wiring issue though. There are cut wires in the engine bay, near the head lamps on either sides. I'm thinking that may be the issue.

Gauges -
Gauges are now working! Just need to tackle the speedometer, but it's not urgent. I can generally tell if I am speeding, though this V8 may give me the urge to have a lead foot.

Wash fluid dispenser -
Unfortunately, I didn't find the fluid dispenser on the floor. I will check around some more... though I have a feeling, based on everything else that has been cut out, that it is a case of cut wires/missing components.

Thanks much.