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1990 Mercedes Benz 300E
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Discussion Starter #1
I have read several w124 evaporator rebuild DIY articles on the web and in general they are all excellent but as always, God lives in the details.

I would like to contribute some fine pointers to my own recent experience performing this repair and I will leave it up to the moderator to decide if it merits inclusion into the DIY section.

770 - center vent removal. When removing the center vent, realize that the right side fastener is a screw but on the left side there are spring tension clips inside the vent. I broke these trying to get it off. Also, the mount for the night time illumination was very brittle (looks like a lot of grease on the assembly) and broke as well. If it breaks try to collect all the little pieces to glue back together again. Replacement isn't cheap (ask me how I know!)

779 - When removing the lower console you don't have to do as I did and remove the carpeting completely... just loosen it around the edges where the carpeting is tucked under the HVAC assembly and floor carpets. Makes it easier as you don't have to spend daylight hours re-aligning the carpet with the fibre backings as I did.

783 - Make double sure you release the steering lock with the key before attempting to remove the ignition assembly. Otherwise you will break the lock mechanism. Mercedes has thoughtfully made a part of the HVAC box out of flexible rubber so the ignition assembly comes straight out.

787 - This is the connector block on the HVAC console by the lower side/ drivers. Make a note of how it goes back together and please don't forget to plug in the 2 pole connector that feeds the evaporator temperature sensor! We don't want to make an ice maker here and neglecting this will cost you disassembly of the lower dash bolster again!

794 - This is the vacuum line that feeds into the cabin to feed the HVAC and fuel economy meter. You need to move this to disconnect the expansion valve. Likely, you will need to replace the rubber connectors like I did.

More to come.
 

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1990 Mercedes Benz 300E
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Discussion Starter #2
800 - After all the fasteners that bolt the HVAC box to the firewall are off you will then need to release the old putty from keeping the box on the firewall. There is a suprising amount of play before it will release. I used a 7" metal prybar to get behind the putty and carefully scrape it away. Scrape 3 sides (upper/right/left) and you should be able to get enough leverage on the lower front vents of the HVAC box to break the lower seal.

801 - the last part of removing the HVAC box is to release it from the lower rear vent channels. Remove the fasteners for the channels and the action is diagonal down/out for them. The fit is really tight and when replacing them the driver's side was much easier than the passengers... a plastic panel trim tool was used to pry the plastic in place... helps if the plastic is a little warm as well.

804 - the HVAC box is easier to work on in the comfort of your own HVAC-controlled environment so bring the whole thing indoors.

811 - The proper way to unclip the pods from the HVAC box is at the pods... not on the end of the arms where you will most likely break an irreplaceable piece of plastic. I used a slim blade to lever on the lower slots (lever down and out) to unclip the pods.

815 - don't assume that parts # = useable parts for the pods. For 2 of the pods (recirculation and defrost) the arm lengths on the new pods were different than the arms on the old pods. I kept the old arms on the new pods and after reassembly everything was working hunky-dory.

More to come.
 

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1990 Mercedes Benz 300E
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Discussion Starter #3 (Edited)
838/839 - the new ACM evaporator is a REALLY tight fit into the HVAC box and it needs some coaxing to reassemble the box. I found that bending the wire screen in a little where it meets the plastic detents (at the bottom of the HVAC box) lowered the evaporator enough to re-assemble the box. Take note of how the expansion valve hoses go through the box... tricky to align that area just right. I used duct tape (temporarily) in that area while getting the clips on the other side in place.

842 - clean as much of the old caulking compound off before putting on a continuous strip of the butyl tape. For obvious reasons, keep the backing on the tape till the last moment.

846/862 - I used washer hose to replace the foam drain tubes. You want the new drain tubes long enough to clear the transmission tunnel hole (so you aren't draining into the cabin) but short enough to be able to put back into the car without alot of fiddling. At the end, they were about 3/4" into the transmission tunnel sheet metal hole (whew).

One last point I don't have images for... the ACM evaporator will need its expansion valve "adjusted" so you can put the suction line and high pressure line on properly. The easiest way to accomplish this was with my trusty $10 7" prybar again... put the notch of the prybar against the corner of the expansion valve and press gently towards the center of the car while getting the lines in. Be very gentle as you don't want to bugger up anything @ this point.

Well, that's about it... I'll add if I can think of anything else but this addresses some potential trouble areas when attempting this repair as a DIY that I feel weren't adequately addressed in other reports.
 

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1983 300SD, 1986 560SEL, 1992 300D, 1995 E320 Wagon
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For those of you out there that see this comment, I posted a long video on how to remove the W124 dash and how to replace the vacuum actuator pods for the climate control.

Just trying to spread the word. Note that there are only 2 PN's left of the 6 PN's that are available from Mercedes or aftermarket. On the dual diaphragm pods you can buy one of the two pods that are available, remove their arms (white plastic just snaps it on), and you can take off the old arm from the old pod and transfer it to the new pod. NOTE: This trick only works on the dual diaphragm pods. Last resort you can get just the rubber diaphragm inside the pod that you can replace at a place called Performance Analysis in Tennessee, although you can't order on their website. You have to call them. Their part numbers for the two different diaphragms are 2010 and 2020. On the W124 and W126, you can use one of their diaphragm on the "center" pod, which is a single diaphragm. They are inexpensive, not sure how long they will be in business from the conversation I had with them. . Get a bunch and store them the rest of your life!
 
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