Mercedes W124 Tempmatik HVAC Control Panel Repair & Recap

This is applicable to my 1990 300E-24 - there definitely are differences with other versions / model years.

[@MMWA-DAVE]

CORRECTION: Refrigerant high pressure switch has its own relay and unrelated to the panel, but meh, it was worth testing anyway. Blue coolant temp sensor definitely does go to this. Capacitor values - 25v 220uf and 63v 4.7uf. The 220uf in particular must be of a low profile - If you use one too tall you are going to cry - you will have to dissemble all over again!

[@markhenry1144]

Maaaate, This stuff is invaluable. Thank you so much. (Ps. This is coming from someone who hasn't even purchased a 300CE yet....)

[@TOONACEDRELA]

Excellent tutorial. Will be of great help to many others. Sharing of information is so important in the quest to keep these cars on the road. Too many people give up on them with silly little things that are perfectly fixable.

[@MMWA-DAVE]

for now theres quite a few left floating around and still some new old stock ones available if ordered from mb. I highly doubt these antique crinkly 80’s style boards have been made for years. At some stage there will be none left and we all will be relying on refurbished ones. I wonder if anyone other than motorolla made the controller ic’s - they dont even make anything anymore.

[@TOONACEDRELA]

@@MMWA-DAVE Yep. I bought a couple of spares for very little money years ago from Melbourne wreckers. Put aside for rainy day refurbishment. So far the only fault with mine has been one of the switch red LED's...easy. Incidentally, mine is the snowflake version 124 830 19 85 which was fitted to the .050 and early .051's (mine is April '90). The EPC lists it as superseded to 124 830 29 85 as in your tutorial. It seems that, like the vacuum gauge, it was dropped mid 1990.

[@MMWA-DAVE]

@@TOONACEDRELA heh, coincidentally, i grabbed all of the ac control panels when i was in Adelaide scouring the pick-a-parts last. I understand theres hardly any 124’s left for picking. I did get some very useful parts from those places, many of which ended up on red.

[@drainaudio]

Cheers for posting this, was very helpful with regards to disassembly & a general overview before I got stuck in. Fortunately like everything else on my car a quick tear-down, thorough clean, re-solder of main connections has brought everything back to life. Of particular curiosity were the engage buttons for recirc, EC, fast demist. My EC switch wouldn't engage at all which was causing the compressor to be engaged when not wanted (biggest issue). A good flushing with contact cleaner resolved the issue.......but thorough drying necessary before reconnecting as there is the possibility to create a short within the switch that has your dash lights suddenly coming on via the AC panel. Bit of an initial "oh dear" moment.. 🤣

[@shaazy]

Awesome video as always. I'm diagnosing an Aux fan that won't kick in at high temps. I've a '91 300E 4matic sedan with climate control and dual aux fans. The fans cycle on low speed correctly. However, as temps rise, the high-speed side doesn't kick in at 105 Celcius as it's expected to. My coolant temp sensor is blue and mounted next to cam cover. When I unplug it with ignition on, I can hear the relay click but fans DON'T come on. No fuses are blown. From my extensive reading, it seems like this coolant temp sensor is supposed to signal back to Climate control, which then decides to turn the aux fans on high. Is that how it works? So the problem may very well be in the Climate Control panel?

[@robertbalogh3663]

My temperature wheels don't do anything. The AC button is lighting, (older version) but there is no air conditioning, and the temperature is low even though I adjust potentiometers. What do you think, do I have the same problem like you did?

[@charlestimmis273]

which solder gun with vacuum are you using? I am thinking of opening my w126 automatic Climate control and take a look at it I am guessing it should be a similar procedure, look for bad solders , etc....

[@rfbu]

Great video! Do you have circuit diagram for the back-light? Fuse etc

[@MMWA-DAVE]

I did have a pinout for this tempmatik once upon a time, problem is its not used in the usa so its not easily found online. I wish i saved it. I know someone who has all the paper manuals though.

[@vmlelectronics]

I would have replaced the tantalum capacitors too... Mine has the snowflake version and as my compressor had been ruined, the new one was not identical, not having the speed sensor on it's back, what lead me to a "gambiarra"... I've used the AC ON LED signal from the IC, then used a micro relay after a BC338 to turn on the new compressor; I've supressed the heater system so the rotary potentiometers lost theyr function... I've mantained the original pressostats on the circuit of course and by now I have a digital air conditioner... it works 0 or 1. lol

[@MMWA-DAVE]

this setup would not work with my ocd, i would have exchanged the compressor for the correct version. Both my new compressors were identical to the originals, denso brand out of the box. Hopefully you remember to turn off the compressor during kickdown- without the safety of belt slip detection you risk grenading the compressor internally and sending shrapnel through the entire system.

[@vmlelectronics]

@@MMWA-DAVE your concerns are important but I almost never rum the engine over 3000 rpm and when it's the case I usually turn off the AC. By the time the AC was (barely) repaired I wasn't able to find the exact compressor, so the shop uses a Denso without the sensor, unfortunately... Initially the "technician" installed a switch directly at the AC clutch, out of the thermostats; for luck I've checked It soon after...

[@TofumanFC3S]

16:51

[@MMWA-DAVE]

hahaha, that was a mistake

[@TofumanFC3S]

What a tease

[@chtewimourad9129]

translate your vedios in arabic plz