And only a simple relay if you're real lucky. In the case of MB, they
like to mix all kinds of vacuum and electrical widgets in systems,
particularly the climate control, which is very complex. It's about as
far away from a straight wire to the compressor as you could get. A
simple vacuum leak in the air conditioning controls can disable things.
As I recall, in my 80 300SD, the blower won't even come on unless
vacuum pressure is present.
If you're trying to track this down yourself, I'd get a repair manual
for the car that includes circuit diagrams of the electrical and vacuum
systems. Then you can track it back to what works and what doesn't.
If you plan on keeping the car for awhile, it's money well spent.
I tried repairing a pushbutton module once. Spent days on it, ohmed it
out, replaced burend traces, all checked out. Woulnd't work. Got a good
used one. Still works today.
I've repaired a lot of eletronic gizmos from camcorders to alternators
but this thing is a bloody nightmare.
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
Richard Sexton <See http://rs79.vrx.net for address> wrote:
completely apart put in new relays on the ciruitboard and checked every
component and resoldered all traces (well it was over $300 CDN) but no
cigar >:-/ finally bought one.
ps my predcictions for tomorrow D (1) A (1) germany wins on shootout by 1
Not really, the pressure measurement is just a negative value.
I believe that most of the time what the vacuum does is remove the air from
one side of the piston and the atmospheric pressure actually does the work.
Do you have access to a wiring digram of your vehicle? If so I'd trace the
wiring from the AC compressor back toward the control buttons. Look to see
if you have a relay in the system which could be the problem. On my '81 300D
the fan will not work if the fuse is blown which also (apparently) provides
power to the AC compressor as well. One other thing to check is to make sure
the two plugs with all that wiring are firmly pressed onto the male pins on
both sides of the control module (the one with all the buttons and switches
in your center consule).
Don't know if you have a parts yard in your area but I've bought that
control unit with all the buttons, along with the circuit board and rotating
temperature switch, and also with the fan switch, for about $25 with a
guarantee. Of course I have to take them out myself but it's well worth the
trouble. Only problem is I usually have to get to the yard as soon as the
MBs are brought in to get the best parts. Good luck!
i don't have power at the pressure switch with eng running and fan on
high and dash temp wheel to max blue. system, seems to work fair
[45-50 degrees] when wire to press switch is hooked dierect to battery
even though i still have some air bubbles in sight glass. working
backwards from pressure switch what is next thing i should check other
than the dash control assembly which i have switched 3 different ones.
I don't have the specific wiring diagram for your car but I'll check this
weekend and see what happens on the 300D from the pressure switch back. I'm
naturally assuming you've checked all of the fuses. Not sure if the AC
compressor/pressure switch are on a separate circuit on your vehicle but
that's usually the first thing to check.
gulp.... just bought a factory mbz heat/a/c manual on ebay.... paid
through the shorts... $129.00!! got in a bit of a pissing contest
with a few other guys [musta been in my same predicament] :) ...
how bad did i get gouged??
damn i need this a/c to work and just know i can do it myself with this
groups help and a couple schematics... got 3 mbz books, haynes,
chilton etc... never have i found an answer to a single one of my
questions in one of em.... gonna take a week to get it, will keep
asking questions in the meantime ok? appreciate any and all your
Bought a complete set of four factory MB manuals 3-4 years ago, paid roughly
$300 for the set. In as much as the printed versions are practically
unavailable today that might not be too bad of a deal, especially if it
helps you solve the problem. I know there are CDs available but I understand
the photos are of very poor quality. It takes a long time and a lot of
scanning to get a proper set of manuals put onto a CD. You'd think they
could do a better job than that.
i bought a w126 cd a while back on ebay.. couldn't make it run.. my
son said i dont have a big enough graphics card. i have a dell 1150
inspiron laptop. anyone else make these work? -gary
Yes, the old cd manual gives us hard time with XP... I figured it out.
First, install that old Adobe Acrobat 3.01 that came with the CD (there is a
folder in the CD content if you can't find it) Adobe Acrobat Reader 7.0X...
and reboot if required... Then go ahead and boot up that CD...
That should work.
thanks, will try it today. while i wait for my new a/c manual i bought
on ebay, i figured i would buy and install a new dryer and expansion
valve. and purge the system. i also have a near new compressor i had
on a sd my son wrecked. think i'll put that on. where's best place
online to buy dryer and expansion valve? -gary
Oops... I realized I lost alot of instruction...
1. Install the Adobe Acrobat 3.01 that is in CD...
3. Install the new Adobe Acrobat Reader 7.0x...
4. Reboot if necessary
5. Load up that manual.
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