Hi Guys,
I have a 93 400SEL on which I replaced the evaporator,receiver drier, expansion valve etc by a MB mechanic in his off time at 64,000 miles.A/c blew great last summer till I took a 3 hour`highway ride. Then after 2 hours or so the flaps semi closed and I heard the fan working like crazy but little air getting to passenger compartment. After 25 mins or so it worked fine again.Similar thing happened on the way back.
Since I usually dont take long trips i forgot about till I took a long high speed 65-85 MPH (3 hour ride again) this summer. This time the flaps semi closed after 1 hour and reopened 30 mins later. On the way back from this trip the flaps closed after 1 hour and stayed closed all the way back.They refused to reopen for the next 4 hours even while mechanic was working on it. He looked behind glove compartment checked vacuum lines etc and said it was prolly some switchback valve.He could not get flaps to open .The following morning it was fine again. It only happens on long high speed trips and never in the city even if I am using around town for 2-4 hours .
I just got back from vacation and want to bring it to him again.The last part he was looking at was on passenger side floorboard. He said he can borrow one from MB parts and try it. I see many people talking about the vents here.
I now think that something similar happens in winter months also after a long time driving, that I didnt notice because I dont use the heater much in winter but use the a/c 8 months a year.I keep it on 68 or so year round .
It seems that whatever is happening,is happening sooner now and staying messed up longer now, if that helps at all. I will also try the procedure outlined here when I get to my car in 2 days and show it to him.
Thx In advance
PGP
P.S I love my car like you guys love yours so it very frustrating :)
Well Brett I hope I am in luck. I have seen this post before but I have not gotten my car back from my friends garage to try it. But it is an intermittent problem and I wonder if it will test normal till the problem shows up . Then I can retest it during its phase , but I have to drive for an hour at high speeds to replicate . Does that switchover pack mean anything to you ?
Thx PGP
Well, for $32 it sounds like it's worth buying a new one anyway.
If it doesn't solve the problem, be happy that you have replaced a 12 year old part with a brand new one at nominal cost. I can't help you otherwise. Your problem sounded a lot like Werner's, especially your comment on your mechanic wanting to swap a part located in the passenger footwell, which is where this part is located.
Now that I am back in NYC I am going to print out Goatmans comments and read them more carefully . I have a different situation because my center vents open, just not too much volume. Did not mean to sound ungrateful. Also the other a/c tests I have found here sound very promising if in fact it is the switchover valve block. The page from K6JRF has all the tests to try.
Thx again I will let everyone know how I made out
PGP
Brett can I post this in another thread/forum until I can get my car back. I would like to get as much info as possible and do not understand the thread/ posting concept yet. I am not even sure how my post got where it is ?
Thx
Not quite sure what you mean by "another thread/forum."
I would not recommend reposting the same problem over and over again if that's what you mean. It will be very annoying to everyone. Those that read the forum with interest (also usually the knowledgeable ones who may be able to help you) will typically read all the new threads, so they will see your one post. And you can set your preferences to cause threads with new posts to automatically appear at the top of the forum (but, below any thread that has been "stickied" by the forum moderators). So if someone replies to your post, it will appear at the top.
If you mean other Merc discussion boards, there is mbworld.org and www.mercedesshop.com. Mercedesshop has a more technical leaning, so may be most helpful, but I haven't followed it.
Well I got my car back and tried two diagnostic programs that were recommended so far: setting both wheels at 73 and holding rest button in till display changes, and holding rest anc c/f key simultaneously and everything that was predicted happened.Now I knopw I have vacuum but that I knew before. As I said this only happens after driving high speeds for over 1 hour 15 mins. I toggle from high to low on numbers #1 thru #16 and flaps changed every time.
I need to perform the other tests described by Jerry in which you set one side to high and the other to low to retrieve the dtcs.
Amazing what I can learn from this forum . Will let you know what happens after I do the other tests.I hope at some point the problem will reappear , so I can run all the tests at that time
Thx
PGP
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