Mercedes W126 HVAC Box Rebuild - 1990 Model Year
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- Опубліковано 1 лют 2011
- This shows the result of rebuilding the HVAC box in a Mercedes W126 completely. Replacing the heater core, the AC evaporator & expansion valve, all the foam seals, and any bad vacuum pods. It takes about 8-10 hours to remove the box, about 12-14 hours to totally rebuild the box, and THEN you have to re-assemble everything.
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This video goes over how to disassemble and install new diaphragms from George Murphy and Performance Analysis in Tennessee into the dual diaphragm pods. You have to call him to order, you can't order on the website.
Again, I advocate buying new MB pods first. Doesn't matter which dual pods, the only difference is the arms. The ones that are NLA are becoming more so each and every day. I only put this on here to use the Performance Analysis pods as a last resort down the road for those who were too late to buy them.
I wish I knew if the W123 pods were the same as the W124 and W126. I have never held one to compare the differences.
ua-cam.com/video/SV1XZ5BEtVc/v-deo.html
Billiard felt... God bless you. I just started the process of this, what a rabbit hole. After all the mechanical problems, there is the electrical stuff... 35 year old capacitors on the circuit boards. But these cars are worth it somehow.
Mine is also a 1990. I took the trouble of pulling the cruise control, replaced all the capacitors and resoldered the bad joints... never imagined a cruise control could be so good, its like magic.
I just did a 87 560 sel for a friend , compressor oem , drier, valve , 4 vac pods , vac solenoid wow pretty complicated for 87 , did manage to find a drop flow condensor flow this , makes a world of difference here in s texas
Great work man. I'm slowly sorting one of these 126 cars over on my channel. This is great info. Thank you !
Great job! Finally someone that put a useful video about the HVAC.
Top job and I really appreciate the fact you took the time to post up this video.
Cheers
Excellent video, thanks for posting!!!!!
Thanks for your compliments. So far the result has been excellent, though I think that the air recycle flap needs a slightly thicker material than felt with perhaps more of a spongy quality to aid in sealing. The rim of the box isn't perfectly flat which makes it tricky. I had used two layers of felt around the edge of the flap and foam around the lip of the gox, yet still get a whistle at about 80, same as before. Perhaps the whistle is something else, but I'll have to see.
Thanks, I'll check it out!
Yeah, pretty much all those things were corrected, not to mention finally being rid of bits of dried disintegrated foam blowing out of the vents. I replaced both the heater core and the evap core. The evap core could have just been cleaned in retrospect, but it was so much work to get inside there that I figured I should just go ahead and replace it. The two most frustrating parts were re-connecting the vent cables and hooking up the AC hoses to the expansion valve. Patience is necessary!
This project took me a week from start to finish. 2 days to pull out the dash, wheel, center console, ABS system, air ducts and finally the heater box. 2 days to rebuild the heater box as shown, and another 3 days to put everything back together. Of course I decided to fix every little piece of trim on the way, and that added to the time. As you can see, beware of aftermarket parts. Take your time, and use superior material. The end result is a HVAC that performs perfectly.
It's been a while, but if memory serves it's the pod on the front center of the box, you can see it at :44. Not 100% sure, but I'm as sure as I can be two years later. It is designed so that when it fails the defroster is on all the time.
Could be, though I would check the solenoid coil for continuity as well.
It is pretty hard to mount it back...I've done that 3 times by now. It took about 5 hours to get all things back on...Good luck :)
I have a 560sel, 1986, with only warm heat. i bypassed the monovalve and no change. I suspect a blend door problem, but cant find a actuator for it. Is it possible inside the unit itself?
Luckily I can get to that flap through the glovebox with little effort, no teardown necessary (assuming that's what it is). For me, the biggest test of patience was re-attaching the AC lines to the expansion valve, and the bicycle cables that control the side vent flaps. The AC lines insist on crossthreading, and the bicycle cables have infuriating clips that you have to attach blind. When I was done my hands looked like I was trying to steal food from a badger. Let me know if you need help.
Hi again, I checked the monovalve and the diaphram is intact. Could it be that it is not sealing well when actuated?
The evap was a Behr. It went in without issues and is still working fine.
I thought you said you used a Nissen and had some issues with the pipes lining up and you had to do some modifications with a dremel tool?
@@ronb1057 Evap was a Behr. Heater core was a Nissens.
I'm getting heat while the ac is on what needs to be looked at? I mean they are both running and fighting each other. Thanks!
WOW, inspirational is right! I've got an 82 with a dash swap in it's future, since the one in it looks like the surface of the moon!! NOT looking forward to pulling apart that whole kit & kaboodle! What brand evap core did you get, I was thinking about just doing the ac core (some of the older benz heads say the heater cores dont go bad, but, they must at somee point, and build it to drive it for another 30 years so do it right after watching this video I'm inclined to do the core too
Hi, for the double vacuum pods what role has the bottom diaphragm? although it holds vacuum it will not move at all....
the double element pods allow two different lengths of arm movement.
You will need to investigate the monovalve. It probably needs a new diaphragm.
And furthermore, if you have a vacuum leak anywhere in the HVAC system the loss of vacuum will cause this pod to open the defroster.
what a nightmare,,,,,,,,,,,,,,,,i'm impressed,, how many gallons of scotch did u go thru to get thru this job?
I give all respect to you for taking on such an extensive project. I have a W126 87 300SE with a tiny bit of mold or something in there. Mechanically works fine, even blows fairly cool. Problem is I have terrible allergies, especially to things blowing in the air. I tried a high end, standard shock-treatment-style ozone machine, but it didn't work. Tried feeding it in through the outside intake, and also on 'recycle' with the unit sealed in the car. Running heat and cold for about 25 mins. I feel there is no 'dwell time' inside the box, for the ozone to get into all the tiny crevices and kill the mold/bacteria. So...I thought...can I pipe in ozone into the box (when the car is off) through a tube, into the drain line? Here's one that might work: www.cleanwaterstore.com/OS002290.html#tab=tab1. You know? Pipe it in under slight pressure with vents closed. Do you think that might work? I could even mount this under the hood and turn it on for 2 or 3 minutes after a long drive. I know the rubber seals would be effected negatively. Maybe only use it a few times. Might that be solution for these cars? Thanks for posting the video!
Should have traded it in…