unbearably obvious climate control question (1982 300sd) - PeachParts Mercedes-Benz Forum

its_snowing · #1 11-28-2006, 07:08 PM

hey all -

i have an embarrassingly obvious question. basically, if i had the owners manual that came with the car, i could answer this question. on the blower switch on the dash control, what does the bottom button do? there are two halves to the switch - the top is a white fan, the bottom is an outline of a fan. i just got this car, and am trying to sort through some of its issues (of which there arent many - a possible ball joint, slow sunroof, some bulbs burned out, and a possible electrical issue with the horn/defogger which are sometimes a little flaky). anyhow, i cant help but notice that, while the blower activates when i press the top button, the bottom half of the button doesnt seem to do anything. sometimes i hear some intermittent clicks after pressing it, and then nothing else. also, when the blower is on, the heat that comes through the vents is not particularly hot at all, even at peak driving temps (80 deg. or so).

so a) what does that bottom half of the switch do? b) how hot should the heat be? and c) here is the car:

EDIT: heres another, possible non problem. before starting the car, when all the warning lights go on, i hear the buzz, but the glow plug light is usually delayed, and then tends to come on for only brief little flicker before going off. however, i dont seem to have any problems starting the car. is it possible that a sensor somewhere is just glitching, or can this be a symptom of something else?

#2 11-28-2006, 07:31 PM

Quote:

Originally Posted by its_snowing

on the blower switch on the dash control, what does the bottom button do? there are two halves to the switch - the top is a white fan, the bottom is an outline of a fan.

how hot should the heat be? and c) here is the car

the glow plug light is usually delayed, and then tends to come on for only brief little flicker before going off. however, i dont seem to have any problems starting the car. is it possible that a sensor somewhere is just glitching, or can this be a symptom of something else?

On the blower control, the top button is high speed, the bottom button is low speed, and the middle button is automatic (controls the fan speed based on temperature).

The heat should be HOT when on maximum, just like any other car.

The GP plug light failing to light normally may be an indication of one or more burnt out glow plugs, or it may just be a problem with the indicator (or the bulb). The first thing to do is check the resistance of all the glow plugs to determine if any have failed.

its_snowing · #3 11-28-2006, 07:49 PM

hmm. so, i suppose i have a problem, in that the low setting on the blower is not working, and also the fact that the hot air is more like kind of warm air... thats a problem too. as far as i know - or as i was told - the glow plugs were replaced just before i bought it, so im assuming theyre ok.

i wonder if the blower problem could just be the switch? although, the fact that i just hear intermittent switching noises when the button is pressed could mean something.

its_snowing · #4 11-28-2006, 08:05 PM

oh wait, after further reading, im wondering if hot air doesnt only come through the floor vents, and not the dash vents. im sorry, i am still new to this.

#5 11-28-2006, 08:08 PM

It could be a few things, the "switch" is part of the climate control unit:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41YE16WT23&year=1982&make=MB&model=300-SD-002&category=All&part=Climate+Control+Unit

This unit controls the entire system, including the blower.

The blower motors can also fail, as well as the resistor that controls the lower speeds:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41YE16WT23&year=1982&make=MB&model=300-SD-002&category=R&part=Blower+Motor+Resistor

The heater valve is called a "monovalve" and is also controlled by the control unit:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41YE16WT23&year=1982&make=MB&model=300-SD-002&category=All&part=ACC+Mono+Valve&appChassis=_any

These can also fail, and they can be rebuilt (sometimes)

There is lots of info on the forum about troubleshooting these systems.

#6 11-28-2006, 08:12 PM

Quote:

Originally Posted by its_snowing

oh wait, after further reading, im wondering if hot air doesnt only come through the floor vents, and not the dash vents. im sorry, i am still new to this.

The hot air does not come through the center vents on the dash, they are only for cool air and AC. In defrost mode you should get maximum heat through the defrosters and the side vents on the dash.

toomany MBZ · #7 12-04-2006, 09:57 PM

The fan works, so it is not being "told" to come on at low speed. More than likely you have a cold solder condition in the climate control unit. that would entail removal and repair, a project, that although tedious, can be done. A rebuilt unit runs over $250, and you still have to remove and replace. Not to mention core cost. The monovale is a cheap and easy swap, just make sure you need a replacement. Remove the current one, and if the rubber part is still entact, it's fine. It is located on the firewall, remove two screws, right there it is. Do this with a cold engine, you'll save a trip to the burn unit. If you do not have hot heat, check the temp gauge to see if it pretty much stays around 80c when the heat is on. You may need a new thermostat, easy $20 fix. The slow sunroof is probaly due to - here's a high tech term - gunk. I have two MBZ that have the same affliction. I have purchased a kit to clean out the tube which houses the cable that powers the roof, that Hans built. Do-da, do-da. Anyway, this is a long, laborious, process. I am not looking forward to it, yet will attack albeit next season. To seperate the ball joint, you will need a fork available at your local auto parts store, usually, and upper body strength, not to mention a heavy hammer. I replaced an upper control arm, and tie rod, both of which came with ball joints attached, lucky for me. You will need to make sure you don't crush said joint when installing. Get back with me on that if neccessary. Check to see if you need front wheel bearing replacement, this can be a VERY expensive repair if a failure occurs at speed, I am putting my former mechanic's daughter through college as proof. The defrost is supposed to, I think, be high fan speed and full heat regardless of temp setting. The horn might be something as simple as a loose connection. Does it work at all? Sometimes? Weak? "Have fun in your garage"

JimmyL · #8 12-04-2006, 10:23 PM

Quote:

Originally Posted by toomany MBZ

The fan works, so it is not being "told" to come on at low speed. More than likely you have a cold solder condition in the climate control unit. that would entail removal and repair, a project, that although tedious, can be done. A rebuilt unit runs over $250, and you still have to remove and replace. Not to mention core cost. The monovale is a cheap and easy swap, just make sure you need a replacement. Remove the current one, and if the rubber part is still entact, it's fine. It is located on the firewall, remove two screws, right there it is. Do this with a cold engine, you'll save a trip to the burn unit. If you do not have hot heat, check the temp gauge to see if it pretty much stays around 80c when the heat is on. You may need a new thermostat, easy $20 fix. The slow sunroof is probaly due to - here's a high tech term - gunk. I have two MBZ that have the same affliction. I have purchased a kit to clean out the tube which houses the cable that powers the roof, that Hans built. Do-da, do-da. Anyway, this is a long, laborious, process. I am not looking forward to it, yet will attack albeit next season. To seperate the ball joint, you will need a fork available at your local auto parts store, usually, and upper body strength, not to mention a heavy hammer. I replaced an upper control arm, and tie rod, both of which came with ball joints attached, lucky for me. You will need to make sure you don't crush said joint when installing. Get back with me on that if neccessary. Check to see if you need front wheel bearing replacement, this can be a VERY expensive repair if a failure occurs at speed, I am putting my former mechanic's daughter through college as proof. The defrost is supposed to, I think, be high fan speed and full heat regardless of temp setting. The horn might be something as simple as a loose connection. Does it work at all? Sometimes? Weak? "Have fun in your garage"

Why did the Franklin Gothic Medium font catch your fancy???? Different, but harder to read......

Its_snowing, I love the color of your SD. Not real common, which I like. What is your interior color? Keep those pics coming.
The guys above, even the funky font, have you headed in the right direction. Cold solder joints on the CCU's seem to cause us fits. My blower chooses when it wants to work when I have it on eco mode.....

Shorebilly · #9 12-05-2006, 07:46 AM

Try pressing the little bar between the switch halves....automatic......then drive your car and see what happens......when fan is in "Auto" mode it changes speed as the Klima Kontrol dictates......

I'm not sure which model Klima Control is in your vehicle......BUT.....MB recommends that the system be operated in the EC mode (economy) the air condition compressor will not run in this mode......I say recommends, more like recommends over the 0 mode which is off.....

When driving the vehicle.....rotate the temperature wheel from red thru white to blue, and back......slowly, a little at a time.....there is a sensor that samples inside air temperature and will adjust the fan speed as necessary (also the "monovalve").......this should tell you if the Klima is working....

On my car '85 300D...the air sensor takes air fron the center of the dash, there is a little grill close to 1" square.......I dunno about the "S Class" vehicles......someone else here, maybe "Hatteras Guy" he has a buncha "S Klasse" carz......should be able to help....

SB

SD Blue · #10 12-05-2006, 10:31 AM

Quote:

Originally Posted by Shorebilly

.........On my car '85 300D...the air sensor takes air fron the center of the dash, there is a little grill close to 1" square.......I dunno about the "S Class" vehicles......SB

On the W126 the sensor is mounted in the headliner with the port just over the mirror.

its_snowing · #11 12-05-2006, 11:25 AM

jimmyL, the seats and floor carpeting are dark brown, and the roof panels are that sort of palomino color . i havent seen another car with this same exact color scheme yet. anyhow, i am definitely going to go check on the diaphragm in the monovalve, as it sounds like a likely culprit. on the other hand, my heat does work, and does warm the car up from the lower vents, its just that its on the warmer side of "hot."

the other REALLY annoying issue with the ccu is that the buttons dont stick in very well - you have to really fiddle with them to get them to stay depressed, which im told may be some sort of vacuum problem. i was unable to have this fan issue (no low setting) diagnosed, without fisxing the ccu unit, which i opted against. what i really want to try to get a hold on, now, are those non-sticking buttons. i can live with the blower only on high. my real question is - will the a/c work in the summer? i really cant tell if its doing anything, whatwith all teh cold around here. im presuming that its non-functional.

toomany MBZ · #12 12-05-2006, 07:29 PM

The buttons I think are mechanical, when one is stuck down, nothing else will depress. Sounds like a removal and cleaning is in your future. JimmyL, and everyone else, sorry about the font flop, it is difficult to read, will not use it again, I promise.