Want to install economy gauge on my 91 w124
 

Hey all, was in the junkyard the other day just browsing :D and saw a few clusters on w124's that had the economy gauge that my 91 w124 does not have. When I had my 86 it had it, and I rather enjoyed it, could see how my lead foot was doing and it was something to fill that empty space. I don't remember the setup at the junkyard and I vaguely remember the set up on my 86. From what I gather, the vacuum lines should all be there for it? There should be three, right? Is it as simple as plug and play?

vacuum gauge
 

a single vacuum connection from manifold should suffice .

Thanks, going to the yard tomorrow to go find the part, hopefully it'll be that easy!

Installed the eco gauge today, and it was such a royal PITA... I believe it should have been as easy as connecting a vacuum line from the manifold, but when I installed and put in the new gauge cluster, the warning lights went crazy! My high beam light was constantly on, and then when I put the left turn signal on, my fuel and temp gauge would pulse to the turn signal and if I turned on the headlights only the left signal light would illuminate and no console, A/C or dash lights would come on.

I took it all apart again and came to the conclusion that it had to be the cluster malfunctioning, so I took off all the pins and needles from the new and old ones and swapped the faceplate and eco gauge to my old one, put it all back together and it did the exact same thing, mind you it's about 38oF and dark and I'm working with a small LED flashlight. At this point I'm kinda of getting worried, because if it's not a faulty cluster, it's something electrical that either shorted or went out AKA something I can't fix. So I start messing around with the wires and finally find that the circular 12 pin? connector is the culprit, something in it is not touching as it should messing up everything, all I could do was fiddle with it until it magically started working again.

I was happy because now I was finally done, so I hook everything up (about the fourth time) and realize that the speedo cable is all of a sudden not reaching or anywhere close. This really puzzled me because last time I had the cluster out I didn't have this issue. I pulled and pulled on the cable trying to get some more slack but it gave me nothing, and I tried as best I could to connect it with what I had, but it would just not reach, so I figured it's got to be caught on something inside the knee bolster area, so I take all of that apart and try to find the problem, nothing looks like it's restraining it. I figure maybe it's something under the car that it's stuck on, so I lift the car up and go under and find that, our previous mechanic had zip tied it so it would not hang and he did it in a manner where it would not move. I cut the zip ties and I got all the slack I wanted.

Finally finished!!!! Well, sort of. Because I took the needles off the clusters, I did not put them back on correctly so the oil reads way to high and the temp doesn't go above 80. So I have to go to the junkyard once again tomorrow to get another cluster and swap it one last time and I can finally finish this project. It's nice to see the eco gauge, but damn that sucked REALLY bad.

I thought about doing this a long time ago....

My recollection, admittedly fuzzy, is that the wiring (printed circuit and round pin connector) was not consistent in all W124 instrument panels.

Wasn't worth the effort for a gauge that only told me when I was on the throttle...

There are oddball things the aux cluster manages, for instance, the delay circuit for the low oil level float resides there.

Jim

That's exactly right! As I learned the hard way yesterday! I got another gauge yesterday and put it on, worked great all was well, until I notcied the instrument, window switch lights were not coming on. I figured the little red fuse must be bad so I checked it and low and behold there wasn't one!!!! I was already back home and 30 miles away from the junkyard when I figured this out. So I was not about to drive back once again to get a different one. What I ended up doing was unscrewing the actual instruments without removing the needles and putting it on the circuit board that had the red fuse. Thankfully, you can swap them from one board to the other as all circuit boards have the hole for the eco gauge. So I was finally able to finish. I now have a working eco gauge!

So if anyone is about to attempt this, this is what I advise, it's easy, but can be tedious.

SAVE your working instrument gauge circuit board! (Just in case)

Go to the junkyard and find a gauge and take the vacuum hoses from the doner car. (I'd post pictures, but once you're at the yard, it pretty self explanatory)

If all you could find was a board that doesn't have that red twist off fuse, you're going to have to swap boards or else you won't get any dash lights.

If you have to swap, just unscrew the instruments from the back, you'll see the gold nut that holds them and then slowly and carefully pry up on them until they pop off (No unscrewing of the faceplate is necessary, it all comes off in one piece!)

Once it's off, just put it on the new board as it was on the old one and you're good to go!

I found it was best to feed the vacuum hose through the front of the car rather than from inside (connects to manifold near the transmission bowden cable) poke it through the rubber where you see two other vacuum hoses going and feed it through until you catch it behind the instrument cluster and connect it to the board and you should have a fully functional economy gauge.