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Old 03-22-2002, 06:16 PM
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Join Date: Mar 2002
Posts: 14
Expansion valve change on a 420 SEL

Good evening out there in Benzville! Has anyone changed an expansion valve on a 1990 420SEL? I'm leery of having to pull the two airbags if thats needed to complete the job. Can you access the valve from under the drivers side dash without having to pull the steering wheel? I assume if the evaporator is bad the whole dash has to be removed. I'm not picking up any refrigerant coming from the evap. drain but I am around the accel pedal area. If I get in there and it looks like the evap. is bad too, will I need special tools to remove it? I'm hoping it's just the expansion valve. I know the drier needs to be changed too, but should I replace the pressure switch also? Thank you, in advance, for taking the time to answer my questions!!
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Old 03-22-2002, 07:52 PM
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Join Date: Dec 2000
Posts: 368
Yes, you can replace expansion by just removing bottom dash cover. It's tight, but it can be done. I am not too sure about this, but you might have to remove one of the supports as well. I think it gets in the way and you can't quite slip in the necessary tools. Hope that your expansion is the only problem otherwise you need to remove the whole dash. The 126 is one of the most involved, there are just too many screws.

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Old 03-22-2002, 08:34 PM
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Expansion valve on your 420SEL is likely in same place as on my 91 350SDL(126) - directly above driver's right foot when on the accelerator. Driver may be able to kick it with right toe. Local, best-in-town, AC guy replaced mine about 3 yrs ago. We removed only the panel at driver's knees for access to the valve.
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Old 03-22-2002, 09:51 PM
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Join Date: Mar 2002
Posts: 14
O.K. guy's...thank you VERY much for the info... I was hoping someone would tell me that. I enjoy working on my own cars but I was a little intimidated by the thoughts of having to remove an airbag! Thanks again!
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Old 03-22-2002, 11:05 PM
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Join Date: Jun 2001
Location: Santa Monica, CA
Posts: 2,053
The expansion valve is relatively easy to access, but there is one caveat. The bottom pipe retaining nuts (two) aren't too bad, but don't "horse" the upper ones or you'll flex the pipes and have an evaporator leak that you didn't have before where the pipes join the evaporator (weld).
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)
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Old 03-22-2002, 11:31 PM
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Join Date: Apr 1999
Location: Walnut,CA,USA
Posts: 554
You don't have remove any air bags,just remove driver side under panel,side panel and you must have the right tools to do this job I'll leave this job to a pro "trust me" you don't wanna damage your evaporator it evry costly.
MB STARS Master Guild Technician,17 years MB tech
14 years independent shop owner
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