Sure, I would like to see the control unit! My cruise control havent been working for a while now, didnt bother me much. However I'm keen to resurrect it, so yeah, that would be a nice video!
An update from the other side of the world (France): The information from the Hall effect sensor is used by the cruise control ECU, by the injection ECU and ALSO by the 722.5 automatic gear box IF your car has this option which is the case for my 1992 300CE 24. In that case, if the sensor is dead, you have no 5th gear. However if you take off the gear box ECU you get 5th gear but not the 4th one which is a proof that the problem is likely to coming from the speed sensor and not from the solenoid inside the "extension" of the 722.5 (the difference with the 722.4). About the cruise control module the dead 6 capacitors is a best of ! However if you test these capacitors they could be OK BUT their internal resistance (ESR) could be a little bit too high due to the age. Don't hesitate to change all the 6 ones. This ECU is in fact very sensitive to the aging of these capacitors. There is an excellent video on RU-vid about how to change the 6 capacitors (for a w123, but the principle is the same for the w124 cruise control ECU).
yep i have seen that guys vid, i’ve been changing caps in cc modules since my w116 day’s successfully, I have cap tester that does both capacity and ESR, have been caught out on false “it’s ok” assumptions in the past on other projects 😎
Correct. The hall sensor will cause 5th to engage at 80kph under light acceleration in the 300CE-24. They all seem to be the same. The loss of 5th is almost always electrical. Usually, the micro switch in the gear selector or the cigar shaped connector on top of the loom near the inlet manifold. I have yet to see a defective Hall sensor or HGS control unit as the cause. Yep, removal of the HGS is the standard test to show that you actually have a working 5th in the transmission. People have difficulty finding the location of the HGS unit. In the Australian 300CE-24, it is located behind the passenger side outer footwell kick panel, just in front of the door. I have replaced the capacitors on every control unit in the car.......insurance.
@@TOONACEDRELA I’ve still never played with a 722.5 😎 I understand on the m104.980 cars the hgs module is on the bidirectional serial bus shared between the ecu and EZL to get its engine load information (the manifold vacuum pressure from the EZL)
@@MMWA-DAVE Well, you are going to be better than me on the electrical theory, but I think you're onto it. Fifth engages when you're not under load. If you're giving it a bit of stick it holds off until you ease off on the throttle. If you're on the expressway and you go up a very steep hill, it will change back to 4th. This was a big improvement on the Laycock De Normanville overdrive I had on my manual Mk.II 3.8 Jaguar back in the '70's. You had to engage and disengage it manually by a switch on the dash. Curiously, it had the twin overhead cam XK engine which had a similar sound to the M104.
Thank you so much for you interesting videos. They are priceless. I also got a cruise control problem on my W124 250 TD. It might be coming from the cruise control module. Could you tell me where this module is located in the car ? It'll be so great if I can fix it. Thank you Mate. Cheers.
I am interested on tempomat retro fit on my e220 . Could you do tutorial or short video of each component where they located in the car ,i know it might be much but just asking. Dan
It's interesting to me MB used a cable driven speedo on most W124s. The W126 was electronic from the beginning in 1979. The speed signal is used on the radio for speed sensitive volume on 1991-93 USA market cars. The cruise had been broken on my W126 for years... the problem ended up being the control stalk / switch! I shot some video of the testing, I need to edit it together.
This very fact annoys the hell out of me. I started this video ranting endlessly about the fact that the 126 had electric speedo from the beginning of production. The w124 is a newer chassis but only got electric speedos in the v8’s. It makes no sense to me at all and the mechanical speedo is an endless source of irritation with bouncing needles if the cable isn’t routed exactly right or a little bit worn. Both my cables are new, both have a bit of wobble, RHD cables are much longer than LHD and very sensitive to any careless routing. I deleted that rant and started the video again as i knew it would freak people out hearing me talking about something I strongly dislike about w124’s 😂
@@MMWA-DAVE thinking about it more... what W124s don't have the vehicle speed sensor? Some early carbureted stripper 4 cylinder? Cruise Control was standard in the USA market, along with Auto Climate Control which both need the speed sensor. I imagine many W124s in other markets have at least one system that needs to know vehicle speed, so why have the duplicate cable and sensor? I also wonder what the cost difference was between the drive motor in the W126 speedo vs. the drive cable on the W124. The motor has more parts, but I'd think each part was easier to make than a long, perfect run of cable or sheathing? Does the Tempstat system use vehicle speed? IIRC it's only used to boost the fan speed when stopped on the ACC system. In the USA market the W123 got an electronic speedometer... for the 1981 model year only 😖
@@compu85 I was looking at the wiring diagram yesterday, and yes the push button automatic climate control does use the vehicle speed too (Not the systems used on my cars) Having thought about it some more - The w124 interior is quieter than the w126. The early electric speedo in the w126 is quite noisy in operation when in the dead silence of my test bench. The mechanical speedo is almost silent. It’s possible the quieter w124 interior was too quiet for the early electronic speedo.
@@compu85 heh, probably more an issue on the M103 version w124’s. I remember when they were new and extremely quiet inside. My m104’s are quite loud even with stock standard exhaust systems. The m103 powered w126 is very quiet too.
Hi maybe you or someone you know knows this but what transmission oil should I use for my 717.450 (getrag) transmission. I bought some Ravenol ATF but my gearbox started to making some noises
speedo on this model is strictly mechanical. The vss on the back is for various other functions, the cruise control, the climate control (some models) the stereo (some models) the outside temp display (middle and late versions) and the ecu for coasting fuel cut off etc. Probably other things i’ve forgotten too.
@@MMWA-DAVE since you replied you’ll see this one too I’ve got an near new steering wheel like the one you put in project red if your interested msg back I’m in Sydney
David, do you have the schematics sheet from the Tempomat? If you do and there's no matter related, could you send me a copy (pdf file etc)? I would study it to see if it's possible to use the concept in a manual shift car... If in the end the gadget work, I would certainly share it with you. Of course there's no commercial interest about it, nor reproducing the original, nor selling the possible gadget. Feel comfortable about it, please, as it would be a favor to me and I'd be thankful anyway.
MB offered cruise control in the manual cars, theres just an additional switch for the clutch pedal. It disengages when pressed just like the brake pedal. And yep, its in the standard ETM you can download for free already online. Just google search w124 ETM and dont pay the jerks asking for money, its out there free.
