Ok,this morning as temps drop to freezing the drive into town with
the teenager became interesting since on the left side of the wagon
it vented fresh outside
freezing air, on the right side, hotish air. Turning the dial on left
to almost max made it a bit warmer, click to high and you get heat,
lots of, way too much to live with, otherwise my left foot gets
frostbite.
This has to be resolved.
Fortunately the dealer had two temp sensors for me, so it's either
those, or the potentiometers, or the control unit is screwed, since I
believe the dual mono valve is fine.
Later this evening I tackled the job of confirming the two blower
housing sensors are ok. First of course I found out the fan dial
refused to come off, ???? I know I had it off before to replace the
little bubs in the back lighting and in the control unit!. Pull tug,
plead, invent new words (old words actually), snaps in two. Sigh...
Small vice grips to pull off the inner plastic housing which is as
you know pressure fit on, the outer dial is melted onto it with now
broken stubs. Off to a great start since we've busted plastic, and
this was the easy part. So unscrew upper console wood, remove nuts,
bulbs, place wood somewhere safe far away from the work area, prod at
switch matrix.
The interesting thing here is the dual manual climate control is two
temp dials, a seperate fan speed controller, and vacuum controller
for air vents. Not much there on the control unit proper, but a
large nest of wires and a small 30ish pin conector with a locking
tab, wires head off mostly to drivers side. Has to be a control unit
somewhere else there just isn't anything in the switch assembly. Well
there could be perhaps the manual system is really simple and the
circuit board is the size of a pack of cards? Well since I'm here I
carefully examine temp dial, unscrew right housing, temp dial and
housing comes off. See nice large, clean heavy duty looking
potentiometer. Well that looks reasonable certainly wasn't full of
dust we'll not touch that further. Carefully examine connector, check
tab yes it releases, try to separate. Nope, begs to snap plastic
parts. Fiddle, prod, poke, examine, stand on my head to see
underneath. Nope try some pressure and 30ish pins welded together
creak and the connector releases and the two parts separate. So I
move the switch matrix aside and dangle on driver side. What's left
is a fan speed switch and a vacuum actuator controller pod screaming
touch me and I'll leak air.
Peering about I can see yes on the left according to the w124 USA
manual there should be the temp sensor right behind the control unit
which snaps into the blower housing. Yes it's there. Ok look to the
right, where I suspect the right temp sensor should be. Goodness
knows what the overhead temp sensor does on this car. Yes a
rectangular hole where the right side temp sensor should be. No temp
sensor, just a hole into the right blower housing, no wires, nothing.
Mmm certainly there has to be a temp sensor. I'll bet the evil telco
that messed with the installation and deinstallation of the cell
phone popped it off and it's lying in the bottom of the console.
Look about, nope but odds and ends of non benz wire lurks. Nothing
leaps up and says here am I, that would be too easy.
Ok remove radio. I need to do this to replace it anyway, attempt to
insert radio keys, right one goes in, left one only part way. Fiddle
lots more, then jam left one in. Radio won't budge. Pull, face plate
pops off, well it does that anyway, still no go. Assume I am an idiot
and can't read instructions and swap keys, nope.
Sigh, ok I really wanted to avoid all this extra work, remove center
console storage box, unscrew center console wood, pull back, leaver
out ashtray, or attempt to. Sigh, ensure brake is on, turn power on,
step on brake, put shifter in neutral, finally wiggle out ashtray
assembly, disconnect power cord. Jam two small screw drivers into
stupid lock tabs. Pull radio out, disconnect the 8 pin becker cable,
the 4 pin cable, the ground, and a mystery yellow handcrafted wire
which I think later is the Phone Mute feed wire.
MMm still no temp sensor, It's an inch long, termocouple on end, size
of your thumb, two pins has to be there somewhere. Lots' of wire,
wires for phone coax, cable to 2nd part of becker box, stereo wires,
etc etc. Feed wires to the missing cell controller, few other things.
Poke prod. Finally think surely those engineers ran the 2 temp
sensors in same wire bundle, follow wire bundle back, then foward and
what do you know dusty temp sensor with broken tab leaps out of the
rats nest of wire in the bottom depths of the console.
So deinstaller did it, I doubt the installer did this since at
freezing temps the climate system is quite insane and I doubt the
original owner would have survived the years with an insane system
every winter.
Ok, I replace both temp sensor, wonder if they have been switched?
No the left side was still in, has to be idiot deinstaller ripping
out cell controller behind radio and pulling out right temp sensor by
breaking tab when wires tangled I'll bet. Wrestle with new sensors
for 10 minutes each, sure just push in, if you can just the right
amount of fingers on it. Most likely easy before you install the
vacuum switch and fan controller. Have to insert both hands behind
those and listen to plastic console framework creak...
Finally the new ones pop back in. Later testing shows the two old
sensor have equal ohms at I suppose the correct values, so they
aren't faulty, but one of course has a broke tab. The two new ones
also read the same, since I checked before installing them.
Put switch matrix back on, carefully re-sit everything, wrap all
those stereo leads with electrical tape and ensure misc old cell
phone leads are still wrapped. Don't want to have anything short out
and set car on fire. Note to idiot installer if you wire up an inline
fuse block in electrical tape and stuff into bottom of console area,
and if it blows the owner will hate you later... Look, think,
anything will fry if I turn car on? Ok turn car on, get it a bit warm
and confirm yes the sensors seem to be in the right places, hot on
right gives hot, cold gives cold, and vic-versa. So lets reassemble
the rest of the console area.
The first good point of the evening was the reassembly of the upper
console and ashtray and center console etc only took a few minutes,
everything lined up, no fiddling required, screws just worked, all
the buttons work, switches co-operate. It just all worked. Last time
I did this the switch matrix and wood panel refused to cooperate and
when I replaced the center console wood it was 20 minutes to resit
the window, child safety, and fader switch.
So now the acid test lets take a test drive (a long one say 40
miles). We determine that car now has a SANE climate control system.
Ask for same temps on both sides, you get same temps, no variations
over time, dial hot/cold and opposing wishes. It just all works!!
Wonderful, just like new.
Total price with free labor was one temp sensor, extra parts the left
side temp sensor and the overhead temp sensor. Although I did not
break the tab on the left side sensor and could have reused it, same
for original upper sensor, however price on this items was cheap
($20ish each) and since I had to remove them to test it made sense at
least for me to pre-purchase and assume they were bad, or they would
get busted in removal.
Well give that success I'll consider tackling the next issue, the
outside temp sensor that is flaky. As it became cold out the temp
display shows nothing in the morning, not even back lighting.
Pressing on guage assembly, left side, usually brings it back to
life, or time and warmth does the same.
Would this be a bad solder joint, or lazy connector pin?
On 8-Nov-05, at 1:25 PM, John M McIntosh wrote:
First running the dial on the right side 5-7C colder (seems) to
regulate things a bit.
So I wired up some benz pins/sockets, after doing the relays for my
500E headlights I've a few wires and pins about.
Check for connectivity, then cross connected the two solenoids.
The hot air then switches to the driver's side from the passenger
side.
This seems to indicate the $300+ duo-valve assembly is working and
the signal it is receiving is bad. So either the control unit is
bad, or one of the temp sensors in the left/right heater box is bad.
The temp sensors are $20 each, could I ordered a pair and we'll
look into replacing them. It still could be the potentiometers on
the dials or the control unit, I guess I could disassemble the
console and test them, then find they are bad, reassemble,
disassemble (sigh). Er no it's a bitch to
reassemble the console and align and retighten everything based on
my last experience, plus all the plastic whimpers break me, so
we'll just order them.
On 6-Nov-05, at 5:40 PM, John M McIntosh wrote:
So it appears that right side is heating up, so it could be dual-
valve is weak on one side, or is the control unit flaky?
Mmmm I wonder if I can swap the female connectors or reverse the
connector. That would tell me if the control unit signal
is flake if the swap alters the behaviour from side to side.
Well the connector is specifically designed to disable anyone from
casually or even forcefully
connecting backward. The little plastic tabs scream, touch me and
I'll snap off so I won't rewire it.
Tomorrow I'll visit radio shack and gets some alligator clips and
wire and cross connect things
and see what happens.
That and run the temp dial 5-7 C colder on the right and see if
anything changes.
John
1983 300TDt 358k Kilometers (mobil 1 Delvac)
1990 300TDt 154k Kilometers (mobil 1 Delvac)
1993 500SEL 168k Kilometers (mobil 1 0w40)
