W 202 Auxilliary Fans Low Speed Not Workin

[thevtechater]

my low speed auxiliary fan is not workin guys, my car is a 1994 s200 w202. can anyone help me to rectify the situation?

[vince]

Check the fuses on top of the low and high speed relays. They are inside the fuse box in the engine compartment. After pulling off the fuse access cover you will have to remove the six screws that hold the main fuse box cover to get the top off. There are two relays, one for low speed and one for high speed - one blue and one green if I remember correctly. I don't remember which one is for low speed.

[Arthur Dalton]

Jumper the 2 pigtail wires at the pressure switch located at the a/c reciever/drier with key ON . That will verify low fan circuit
[ fuses/relay/motor/resistor/etc ]. If Yes, then you have a low refrigerant conditionor or a bad pressure switch..most like low refrig.
If NO, then look at relay fuse and resistor behind headlamp as next possibles.

[stevebfl]

My approach is always to consult the wiring diagram. It would seem that for the 1994 year the fuses are no longer on the relays and the pressure switch is no longer a switch but a variable output sensor. This output is evaluated by the push button controller to switch the stage 1 relay.

[Arthur Dalton]

The parts section still shows 94/95 W202 chassis still uses the 2 seperate/ fused relays. They do not , however, show a 202 /C200, only the C220. [ must be non-USA version??]
I think that S200 you have is just a typo..
So, I agree , a schematic for a 202/C200 would make it definate. [ or just look and see if there is a pigtailed pressure sw at reciever/drier....

[stevebfl]

sourced for a 1994 202 actually if one blows up the drawing there are fuses shown in the relays

[Arthur Dalton]

Yes..here they are
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2AO123CS42CM0UGEUC&year=1994&make=MB&model=C-220-001&category=P&part=Auxiliary+Fan+Relay

Almost all 94 I have seen all use the fused sperated relays..the 93 had a fused high fan , but not on the low. My 124 chassis shows 93/94 as that production change, but not ness. on the 202.

But, SB.... I believe you to be correct on the primary/sensor side of the fan circuit b/c the parts does not show a pigtail pressure sw for 202 like they do for 124. They show the variable sensor you mention and that would control all funtion inputs..[ meaning pigtail is no longer used on that chassis]

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2AO123CS42CM0VQHTF&year=1994&make=MB&model=C-220-001&category=R&part=A%2FC+Pressure+Switch

So, the secondary/load side uses the fused relays and R15 dropping resistor just as the 124 of 94/95 , but I do not think the sensor is pigtail pressure, as you mentioned . [ but only on the 202/C class]
Does your schematic show that sw. ?? [ i do not have a 202 schematic]

A note to the poster..if you find the original 15A fuse on top of the low fan relay to be the cause of your complaint, [ which is common], be aware that Benz has allowed a change to 25A on that circuit..evidently they had found the 15A to be slightly under-rated for low fan. You may want to try a 20A first. High is still the 30A.

[thevtechater]

the fuse and the relay are fine, i've had them checked by a mechanic.

i've been going trhu the threads here in the forum and i've come to learn that in the 124 chassis, the low speed auxiliary fan is triggered by two variables. first, the water temperature and second, the pressure level on the hig-pressure-side of the climate control system.

Now what i need to know is, does the aux fan system in my 202 chassis works the same way?

Most of the shops here in my town said that the control unit for the aux fan (some say, some kind of a potentiometer?) must have gone wrong and a new one will cost almost 500 dollars (for the sake of comparison, i'm informing you that the minimum labor wage in Indonesia as we speak is around 55 dollars -month that is-).

If the cooling system on the 202 works the same way as they are in the 124 then maybe there's no problem in my control unit.

Also, it will be very helpful if anyone could tell me where this aux-fan 'control unit' is located on my 202?

Thanks for reading this guys.

[thevtechater]

youre right arthur, its a typo, sorry,

[thevtechater]

and steve, thx for the schematics, i'll print them and bring 'em to my indie

[thevtechater]

and one more thing guys, it's embarassing to ask but, where's my dryer located?

[Arthur Dalton]

The problem here is in the US we do not have the 202 /C200, so we are using info on 202/C220 in hopes that the systems are the same...
So, I would check a few comparisons and that may narrow it down.

First, the drier is a small tank that the refrigerant lines go to near the front condenser [ near radiator] That is where these switches are located [ on the drier]

If you have this sw

http://catalog.worldpac.com/mercedesshop/sophio/image.jsp?title=A/C%20Pressure%20Switch&url=http%3A//img.eautopartscatalog.com/live/R105475741ACM.JPG

you have the variable sw that SB is talking about and that feeds the Control panel the info for the fan.

And if you have the pigtail sw , then it controls low fan and can be jumpered to check the fan circuit [ like the 124s]
Here is that one

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2AO123CS42CN0N6R80&year=1994&make=MB&model=E-320-001&category=R&part=A%2FC+Temp.+Switch

See what you have on the drier and that will tell which system you have.

Also, I noticed that you mentioned in a post that low fans circuits are controlled by /ac and coolant temp..The coolant temp sensor is the blu 2 wire one and that is for HIGH fan..it has nothing to do with the low fan and is a completely different circuit and relay. [ just so you do not confuse the 2]
Low fan is for airflow assistance to the condenser when the a/c highside pressures or temp get into a danger zone..but, if the a/c system does not have the proper refrigerant level, you will not see a low fan b/c the system never gets to that danger zone ...it is not capable to get there b/c it does not have that high pressure capacity if the refrig is level is low..that is what makes low fan diagnosis a little tricky and why gauges to monitor high side pressures are used.
See what you have down there . If you have the pigtail setup, just jumper and see if fan comes on..if no pigtail, that test does not apply.
I would also do one quick check that is common on No low fan complaints.
Behind the headlamp [ left] is the Resistor that drops the voltage to accomplish Low fan.. It is common to see the wires from the relay going into this Resistor burn off or make a poor connection b/c of failure from heat fatique..[it is a ceramic resistor and runs hot/dissipates heat ]
A quick check there may save you a lot of trouble..

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2AO123CS42CN0OD3FJ&year=1994&make=MB&model=C-220-001&category=G&part=Aux.+Fan+Resistor

If you look at that schematic SB posted , that part will be R15...that is needed for LOW fan and if wires are bad here , that is your problem. It is not used in the HIGH fan circuit.

[stevebfl]

The schematic I posted is also for the system that uses a pushbutton display. You could easily have the three knob manual system. The system in the drawing has the fan relays turned on by N22 which is the AC pushbutton controller on the dash. I'm not sure about the other system.

[thevtechater]

okay, thx so much for the info, i'll check it as soon as i'm home today.
and steve, yes, i have a three button knob.

[thevtechater]

Arthur, Steve, i have found both the switch and the resistor you and SB talked about. the resistor on my 202 is located infront of the condenser, around the middle of the grille and the swith is located on top of the dryer which is situated behind the left (passenger side on a right hand drive car) headlamp.

--my engine code is M111 i think its the same as the C220, since my friend's c230 Kompressor also has the same engine designation. the only difference is that mine uses a manifold pressure sensor rather than a hot-wire MAF.--

what do i need to do next?
How can i check the condition of the switch and the resistor?
i havent go to my mechanic yet but as far as i can see, the cables that run into the big resistor are fine , nothing burnt or broken.

one other thing, i think the efficiency of my radiator is dropping (either that or the global warming has really effecting the climate of my town) , basically, the merc runs hotter than it normally does, can you give me an info on how to properly flush the radiator, and then bleed the system out of trapped air afterwards in the 202 chassis?

I really appreciate the effort that you guys have put in answering this thread, i imagine u guys must be very busy yet you still squeeze time to help me out, really do appreciate it, thx again guys.

ps: if you guys wouldn't mind to give me your postal address, i would gladly send you some rather exotic souvenir from Indonesia.