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A/c pressure switch

French02chris

E500E Guru
Member
Hello.
On my way from the beach today, my ac stopped working..
So upon inspection, I saw some freon leak near the ac drier..
It does look like my pressure switch is leaking.. I cleaned it, then run the car, and I could see tiny bubbles on the switch.

Is it something easy to replace or do I need to bring it to the mechanic? As I don't know if the freon has to be evacuate first!?!?
IF I can do it, what size open wrench does it require??

Thank you
 

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To replace either switch you must evacuate the refrigerant, replace the switch, vacuum the system, and recharge. It's DIY'able if, and only if, you own both a set of manifold gauges AND a vacuum pump. Even better if you have a tank of R-134a and refrigerant scale, as charging from cans is not precise. If you own none of this stuff, have a shop do the work.

Buy OE/Genuine for the safety switch, 124-820-83-10... the aftermarket Behr is made in Taiwan and @M104-AMG reported several failures. Ditto for the red-color aux fan switch 004-820-68-10, ACM had been reboxed OE but I'm not sure if that is still true... do not get the Mahle-Behr one for half the price. OE isn't that expensive and the cost to evacuate/recharge isn't worth the gamble.

The receiver/dryer is NLA, don't let the shop talk you into replacing it with a garbage $15 Chinese unit. Leave it alone.
 
To replace either switch you must evacuate the refrigerant, replace the switch, vacuum the system, and recharge. It's DIY'able if, and only if, you own both a set of manifold gauges AND a vacuum pump. Even better if you have a tank of R-134a and refrigerant scale, as charging from cans is not precise. If you own none of this stuff, have a shop do the work.

Buy OE/Genuine for the safety switch, 124-820-83-10... the aftermarket Behr is made in Taiwan and @M104-AMG reported several failures. Ditto for the red-color aux fan switch 004-820-68-10, ACM had been reboxed OE but I'm not sure if that is still true... do not get the Mahle-Behr one for half the price. OE isn't that expensive and the cost to evacuate/recharge isn't worth the gamble.

The receiver/dryer is NLA, don't let the shop talk you into replacing it with a garbage $15 Chinese unit. Leave it alone.
My dryer is one year old... Replaced it last year when we did the compressor..

So, since I can't evacuate the system myself, I will bring it to the mechanic..
Hopefully, it's not that expensive.. Lol
 
Just a comment here. A few days ago I had to replace a 4 yr compressor on my 94 E320. I also replaced the receiver/dryer. I'm pretty sure the shop will have to R & R the R/D in order to replace the switch as there's no room to get a wrench on that switch in situ. A little labor involved. Not sure if U need to replace the 2 hard line O rings but they're inexpensive.


Regards,

Peter
 
Peter, why is a 4-year old compressor failing? What's the symptoms / failure mode?

The 6-cyl receiver/dryer is also NLA, only Cheap Chinese available now. If you have OE or OEM Hansa, make sure they re-use the same dryer.
 
Dave, It was a Japanese produced Denso unit bought on Amazon. I thought it was a section of the suction hose as it was wet and 29 years old. I went to the trouble of removing the hose and having the front section (next to the compressor) replaced at a hose shop. My mechanic friend at the MB dealer where I work charged the system and confirmed it was the compressor leaking, not the hose. Of course no warranty at 4 years. Fortunately compressors aren't terribly expensive and I did the R & R ( bit of a pain lying on your back ).

I believe the failure was due to a lack of oil. Some how virtually all of the oil leaked out. When I dumped the oil out of the old compressor almost nothing drained out. Manufacturing defect or I made some error when adding oil 4 yrs ago. I did see a note on this installation to stand the compressor on end for several minutes to allow oil to saturate the front seal in addition to spinning the pulley to distribute the oil.

Regards,

Peter
 
To replace either switch you must evacuate the refrigerant, replace the switch, vacuum the system, and recharge. It's DIY'able if, and only if, you own both a set of manifold gauges AND a vacuum pump. Even better if you have a tank of R-134a and refrigerant scale, as charging from cans is not precise. If you own none of this stuff, have a shop do the work.

Buy OE/Genuine for the safety switch, 124-820-83-10... the aftermarket Behr is made in Taiwan and @M104-AMG reported several failures. Ditto for the red-color aux fan switch 004-820-68-10, ACM had been reboxed OE but I'm not sure if that is still true... do not get the Mahle-Behr one for half the price. OE isn't that expensive and the cost to evacuate/recharge isn't worth the gamble.

The receiver/dryer is NLA, don't let the shop talk you into replacing it with a garbage $15 Chinese unit. Leave it alone.
:update:

I am preparing to re-do the A/C system on my 560SEC, including the compressor, receiver-drier, A/C temp and pressure switches, Schrader valves and caps, hoses, and so forth. The following two switches that screw into the receiver-drier are THE SAME parts as used on the E500E, and 400E420.

I ordered MB components from MB of Annapolis, and received the following:

Temp Pressure (fan) switch: part number 004 820 68 10
Made in China. I believe this is the same as the ACM switch, re-boxed, but with the MB part at a significantly higher price. Was shipped from Germany.
MB list price: $56.00; discounted: $41.88.
Aftermarket price: ~$35-40
IMG_9102.jpeg IMG_9103.jpeg IMG_9104.jpeg


Pressure (safety) switch: part number 124 820 83 10
No obvious COO. This switch is marked with "TRW" and has the MB star and part number on it.
MB list price: $103.00; discounted $77.08
Aftermarket price (non-TRW): $10.00 (Four Seasons); $14.00 (Mahle Behr)
IMG_9105.jpeg IMG_9106.jpeg

Separately, the receiver-drier I got from MB is a Hansa unit, made in Germany.
Production date was May, 2023.
Perhaps there is hope for E500E receiver-drier units...
MB list price: $182.00; discounted $136.25
IMG_9101.jpeg IMG_9100.jpeg
 
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The 6-cyl receiver/dryer is also NLA, only Cheap Chinese available now. If you have OE or OEM Hansa, make sure they re-use the same dryer.
By the way, Denso work instructions I believe say that you MUST replace the receiver-drier with a new unit when replacing the A/C compressor.
IMG_9108.jpeg



I believe that unlike many other components, because it is a rather "passive" part as to what it does, the receiver-drier can be successfully replaced with an aftermarket Mahle Behr or other "name brand" unit, even if made in China.

I would be hesitant to re-use an OE/OEM unit, even if made in Germany, if refurbishing the entire A/C system. That said, I would also NOT use a no-name (or URO, MTC, Hamburg Technic, APA, etc.) overseas-made receiver-drier.
 
Temp Pressure (electric fan) switch: part number 004 820 68 10
Made in China. I believe this is the same as the ACM switch, re-boxed, but with the MB part at a significantly higher price. Was shipped from Germany.
MB list price: $56.00; discounted: $41.88.
Aftermarket price: ~$35-40
That's a shame even the dealer switch is coming from China now. These had been German-made, IIRC.



Pressure (safety) switch: part number 124 820 83 10
No obvious COO. This switch is marked with "TRW" and has the MB star and part number on it.
MB list price: $103.00; discounted $77.08
Aftermarket price (non-TRW): $10.00 (Four Seasons); $14.00 (Mahle Behr)
The TRW-branded switch is ONLY available as OE/dealer. I would not trust the $10-$14 Chinese copies.



Separately, the receiver-drier I got from MB is a Hansa unit, made in Germany.
Production date was May, 2023.
Perhaps there is hope for E500E receiver-drier units...
MB list price: $182.00; discounted $136.25
Nice! I wonder if the 126 Hansa unit can be adapted for the 124. :scratchchin:



By the way, Denso work instructions I believe say that you MUST replace the receiver-drier with a new unit when replacing the A/C compressor.
Yup - they always want a new drier with a new compressor for warranty purposes, although I don't know anyone who has had a compressor fail within warranty and need to get it exchanged.



I believe that unlike many other components, because it is a rather "passive" part as to what it does, the receiver-drier can be successfully replaced with an aftermarket Mahle Behr or other "name brand" unit, even if made in China.

I would be hesitant to re-use an OE/OEM unit, even if made in Germany, if refurbishing the entire A/C system. That said, I would also NOT use a no-name (or URO, MTC, Hamburg Technic, APA, etc.) overseas-made receiver-drier.
For the 124, the issue is there doesn't seem to be any name-brand replacements available... only no-names.

IMO, if there was not system contamination from Black Death or an exploded compressor, re-using the old drier should be safe. It's just a metal container with a dessicant desiccant pack inside.

@Klink?

:klink:
 
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Yep, hating to see official MB products made in China. I was assuming that the TRW pressure switch was probably from their "good" line of products and made in Germany or Europe somewhere. Too much of a price differential with the cheap Chinese stuff to be made there.

The fan switch price from MB was much closer to the aftermarket stuff, which is another giveaway. If you look at a photo of an ACM fan switch, you will see that everything is identical to what I posted. Note that AutohauZ is calling the ACM switch, "OE."
0048206810OE.jpg
 
I bought a couple of the ACM red switches in 2021, and they were reboxed OE with the Star logo and MB part number. But, I don't think there was any COO on the package. I wonder when they started making these in China. Photos of the Hella/Behr aftermarket show a label with "Made in Taiwan".

:runexe:
 
Following up, it appears that the 124 and 126 receiver-drier units are dimensionally essentially identical. They have different layouts as to the hold-down tabs, though.

Photos of each and together, below.

Boxes of each. Mahle-Behr aftermarket for 124, Hansa for 126.
IMG_9173.jpeg IMG_9174.jpeg IMG_9175.jpeg


Physical looks of each.
IMG_9176.jpeg IMG_9177.jpeg


Labels of each, along with COO.
IMG_9179.jpeg IMG_9178.jpeg


SIDE-by-side comparison.
IMG_9180.jpeg IMG_9181.jpeg


Rough measurements at bottom.
IMG_9182.jpeg IMG_9184.jpeg


Connector orientation with hold-down angles.
IMG_9185.jpeg IMG_9186.jpeg
 
Gerry, I can't quite tell from the photos, but does the 126 unit have provision for both pressure switches?

Also, you may know this already, but your new Mahle drier is for a 4/5/6-cyl 124 chassis. The ports are aimed differently compared to the V8 driers. The 6-cyl unit can be made to work in the 034/036 as @Kridre described near the end of this thread. The pipe from the condenser must be bent to align, along with some mods to the brackets.

:sawzall:
 
Gerry, I can't quite tell from the photos, but does the 126 unit have provision for both pressure switches?

Also, you may know this already, but your new Mahle drier is for a 4/5/6-cyl 124 chassis. The ports are aimed differently compared to the V8 driers. The 6-cyl unit can be made to work in the 034/036 as @Kridre described near the end of this thread. The pipe from the condenser must be bent to align, along with some mods to the brackets.
I am aware that the 124 receiver-drier is NOT the same as the original NLA V-8 W124 units are, per the thread you mention. I actually have two spares of the 124 receiver-drier, from two different manufacturers.

Yes, the Hansa 126 unit does have provisions for both switches -- the system pressure switch and the fan control pressure switch.
 

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