Lets Play Name that Wire! 87 300D turbo - PeachParts Mercedes-Benz Forum

a2t · #1 06-27-2007, 07:14 PM

The wire shown is coming from the block behind instrument cluster. Its disconnected on my 87 300D, and Im wondering where the heck it goes?

My cruise is not working, wondering if this could be culprit as Ive replaced/tested all the usual suspects...

Thanks!!!

in this pic, its the wire coming off front of box

heres the wire! where does it go??

x53/5 shown

x53/5 doesnt appear on pg 116/2 ???

Think this is a wire that use to go to old factory radio??

psfred · #2 06-27-2007, 08:25 PM

More likely it's the wire to the Hall Effect pickup in the speedometer.

Neither wiring diagram is going to help you much, the 87 does NOT have electronic engine control (just idle speed control).

You will need a diagram for the 87 300D.

Faulty cruise control on these cars has three failure points:

1. Amplifier solder joints cracking

2.Actuator draws too much current, causes #1 sometimes, check before replacing amplifier

3. Bad Hall Effect pickup in speedo (causes uncontrolled speed, especially "runaway".

Bad stop lamp will also cause it to fail to run (it grounds via the filaments in the stop lamps, that way there is no voltage when the stop lamps are illuminated).

Peter

Peter

a2t · #3 06-28-2007, 09:53 PM

I tried plugging it into hall effect sensor on back of speedo - it doesnt fit. Plus theres already a green/yellow wire attached there that does fit.

Ive replaced cruise amp, test cruise actuator, and made sure all tail bulbs are correct and working. Still no cruise...

Anyone have specific 87 300D wiring diagram??

a2t · #4 07-03-2007, 11:07 PM

could this holiday be the one that I fix thissS??????

Jeremy5848 · #5 07-03-2007, 11:48 PM

OK, I just went out and pulled the cluster. The green/yellow wire in your photo comes out of the block and goes to the single pin on the back of the speedo. That is the speed sensor and if it isn't connected and working then your cruise control won't work. I am certain of this and my cruise control works.

The plug on that wire has to be oriented so that the wire comes out of the plug pointed up or the plug won't go onto the pin. Maybe that's why you couldn't get it to go on. Whatever wire you do have on that pin is the wrong one.

Ignore the following, which was written before I pulled the cluster.

====================================

When I had my '87's cluster out last April, I mapped all of the wires and indeed do show a green with yellow stripe single wire like the one in your photograph, going to a single pin contact on the back of the speedometer. But if you've already got a connector there....

I remember seeing that block, too, because one of the jobs I did in there was to replace the warning module. If the '87 doesn't have electronic engine control (and I admit I don't know the beast well enough to answer) then maybe that wire doesn't go anywhere -- maybe it is unused in this model.

In your picture of page 137/1, notice the green/yellow wire going to pin X2 ("Speed output") on the Speed Sensor. X2 is a one-pole connector, your diagram says. That wire, in the diagram as well as in your photo, is coming directly out of the block. The other wires attached to the block have little half-circles where the wires go into the block. Those half-circles are connectors. The green/yellow wire doesn't have a connector. That is the wire that should go to pin X2, the Hall Effect speed sensor -- yet you say there's already a wire to the connector and the one in your photo won't fit. Therefore, I'm stumped. Without that signal, the cruise control won't work. Are you sure that the green/yellow wire from the block

Jeremy

a2t · #6 07-05-2007, 11:30 PM

Thank you very much! I know its a PIA to pull the cluster!!

So the wire in question on your model - was it pretty long, like 18" long as shown in my pics above? I tried to plug it in where you say yours is going, but it just wont fit. The pin is wrong size. WTF?

Frustrated. Maybe I can force it. And, I wonder why there is already a wire with connector on it that plugs in there, and fits perfectly, but doesnt go to that block.

If you say the wire on your model is 18" or so in length (obviously too long to go from block to back or speedo) and it fits, then that must be it. Someone must have screwed with wiring on mine and got them mixed up. Talk about needle in haystack. I wonder where the wire that is plugging into the speedo now is supposed to go then. Flux capacitor.

I will pull entire cluster and diddle with this until I figure it out. Im 2 seconds away from buying radio shack stand alone CC and rigging that up, although thats another mountain to climb Im sure.

Again, my sincere thanks for helping. I owe you 1 case of beer.

Jeremy5848 · #7 07-06-2007, 12:54 AM

...we're having some heat here just about now (although not as bad as the desert southwest -- "but it's a dry heat")

Yes, the wire in my '87 is a good foot long or more and definitely goes from the single pin on the back of the speedo to that block, with no connector on the block end of the wire.

It's really frustrating for you, I know, to come up with a connection that doesn't make sense. Here's a suggestion: strip about half an inch of insulation from a piece of 18 or 16 gauge wire. Bend the stripped wires back over the unstripped wire and poke this pseudo-pin into the socket. Tape it down. Strip the other end and wind the wire around the pin that is too big. Insulate it with tape. Now you have a connection, jury-rigged though it may be. Go test the cruise control. Let us know what happens.

Never trust what a PO has done (and be cautious of the stuff you do yourself).

Jeremy

a2t · #8 07-06-2007, 05:59 PM

Quote:

Never trust what a PO has done (and be cautious of the stuff you do yourself).

True!! Alright thanks for confirming. I will get down there and rip out the cluster and see if I cant get that long wire routed to behind speedo. Wife is about to have a kid so might be on hold for a while!

Thanks for your help Jeremy (and others)

a2t · #9 07-08-2007, 12:16 AM

You guys were EXACTLY right! That single wire DID plug into speed sender on back of speedo, and the wire that some bonehead had plugged in there was infact coming from the ACC. So, the cruise amp was never getting a signal. That block behind dash is just a mulitpin connector so the speed signal can go out to various places.

I plugged it up correctly and GUESS WHAT?!@ WE GOT CRUISE!!!! After 2 yrs troubleshooting...

Thanks a million times Jeremy and others.

Jeremy5848 · #10 07-08-2007, 12:22 AM

At least the speed sensor was working. Would have been a shame to finally get the wiring correct only to discover that the speed sensor was dead. I'm glad we were able to help -- isn't this forum great?

a2t · #11 07-08-2007, 09:28 AM

Quote:

isn't this forum great?

Y-E-S!!!!!!!!!!!

so what do you know about sunroofs

Jeremy5848 · #12 07-08-2007, 01:39 PM

I know that mine doesn't work, you can hear rattling when you press the switch but there's no motion. That means the motor is good but the mechanism has broken. It is said to be a PITA to get at. There are some threads here where people have done the job themselves. The factory instructions all start with "open the sunroof half way" which I can't do. My indy says it will cost about $1000 to have him do it.

a2t · #13 07-08-2007, 09:16 PM

Same here. These cars are all alike! Same quote from and Indy too. I tried to pull it apart once, got half way into it and gave up. I know what you mean about step 1 of instructions. I wonder what other 99.9999% have to do? Haha. I will bask in my glory of working cruise for a few weeks (working well, too - holds speed dead on, which is no small feat at 80 mph up hill in old benz diesel running on WVO!!).

Thanks again man. Im just wondering who the heck got in there and switched wiring around (and what else is back asswards).

babymog · #14 07-09-2007, 10:26 PM

If the sunroof cable is broken, you should be able to push the tip-up door up enough to reach in and push the sunroof transport rearward, then disconnect the front of the headliner, push the roof open further and remove the headliner up and through the roof. My 124 came with a broken cable and this worked for me.

Jeremy5848 · #15 07-10-2007, 01:18 AM

Quote:

Originally Posted by babymog

If the sunroof cable is broken, you should be able to push the tip-up door up enough to reach in and push the sunroof transport rearward, then disconnect the front of the headliner, push the roof open further and remove the headliner up and through the roof. My 124 came with a broken cable and this worked for me.

That sounds like something I would like to try after first seeing a W124 sunroof in action. Having never seen one work, I'd rather not mess around blind and make it worse. At least it doesn't leak in its present condition.

In any case, it sounds like you're saying that removing the headliner is an important first step? What's next?