air con/fan queiry

[turbopete]

got home from a trip out today. temp guege reading about 90. air con on. only 1 of the fans at the front of the radiator was running. is this correct below 100? the car has a viscous belt driven fan at the rear of the radiator, 2 electric ones at the front.

 

[mikestrivens]

The aircon fans are pressure related not temperature related. I could be wrong but I think both should activate at the same time. Someone more knowledgeable will be along shortly with the definitive answer.

 

[turbopete]

thanks. i wondered if 1 was for aircon and the 2nd was an auxillary cooling fan? maybe just another job to add to my list!

 

[Number_Cruncher]

The second one is driven by a belt from the first.

 

[turbopete]

so it could just be a broken belt? at first glance it appears they have a motor each but i could be wrong on this fact. are the belts available separately, does anyone know?

 

[bigasotonuk]

Hi,
The 2 fans in front of the radiator are switched on/off by refrigerant gas pressure via pressure switches in the refrigerant line. Both fans should operate together, early MB's with twin fans did have a belt driving the second fan from the first as number cruncher says, but i believe yours will be the same as mine and the individual fans have their own motor.

 

[turbopete]

well there was onlt the one on the passenger side working. maybe that explains why the aircon isnt as instantly cold as dads 203 is. mine seems to take a few mins before it gets going properly. that could be a job for another day though

 

[television]

Sorry to stir this thread up,, there are 3 versions of the fans, there is the single fan type where the fan turns on at 104c, the second version uses a double fan belt driven as said, it also comes on at 104c, the third version has 2 stage fans, the first comes on at 104c and the second at around 110c I believe

 

[turbopete]

glad your back Malcolm. think i will have to get it hot with the a/c off to see if the fan was for the a/c or cos of temp. ive never seen 100 on the guage yet! i wish id saved my big brain teaser for you now instead of posting it 2 or 3 days ago! ive got parts prices, just cant decide what to try first!

 

[bigasotonuk]

Hi,
Your car car has a water pump fan for engine cooling, as refrigerant pressure increases with temp. there is a slight possibility of the 2 fans starting as the ambient temp. around the engine increases as the engine warms up, and warms up the refrigerant lines.
When I had my system was recharged, and with the charging gauges still connected he checked the fans were coming on/off as they should this he demonstrated to me and I watched as the gauges hit a certain pressure the fans come on the refrigerant gas pressure then reduced slowly and as soon as it hit the lower level the fans cut out, this was constant and I witnessed this approx. half a dozen times, and it was the same everytime.
IIRC my fans have run even when the engine was,nt up to temp. thus eliminating engine cooling theory.
Please bear in mind my car is a C class AMG with electronic single zone climate control, though a lot of MB systems are generic.

 

[bigasotonuk]

Hi,
After studying some A/C wiring diagrams I think I have sussed out why me and Malcolms views on what turns the twin fans on/off in front of the radiator are conflicting.
Though the operation of the fans is primarily for the A/C system, there is a link between the engine ECU and the A/C control unit, so this is possibly a temp trigger feed so the fans can be called into action if the viscous unit can,t cope with the engine temp.

 

[turbopete]

tried again this morning. car running at 80, a/c off no electric fans running. switched a/c on, blower started blowing colder, went to front of car an still no electric fans running, so i think Malcolm could be right and its effectively an additional 2stage fan set uo that operates at higher temps to assist the engine driven fan. incidentally there was a noise that sounded like a fan with the a/c running. however i was looking at the car from the front and the 2 in view, behind the grille were not running

 

[LYNALL]

Mine has the 2 elec fans in front and one has the motor and the other is belt driven, easy to tell as on the belt driven one the fan hub doesnt stick out so far as the one with the motor in, when i removed fans to replace the condensor i noticed the belt had flipped upside down and was running on its back, was easy to rectify.



Lynall

 

[television]

One day i would like to do a write up on the differences on these fans, it is a year thing where the differences come in, and it applies to quite a few models, even the 129 has 3 different systems over the years, on most the 2 stage cooling came in in 1999

 

[turbopete]

so its possible mines an oddball on a crossover point. typical! its a 1999 pre facelift if that helps anyone

 

[television]

so its possible mines an oddball on a crossover point. typical! its a 1999 pre facelift if that helps anyone

Sorry I had to laugh out loud,,almost every post that I have to check on is in the middle of a cross over point, the 202,210 and 211 have 4 different fuse box layouts, all by date and not be the Vin series number

 

[turbopete]

well at least ive given you a laugh today. cant be all bad!

 

[bigasotonuk]

Hi,
I still maintain that these fans are primarily for the A/C. The fans may not be running as the refrigerant gas have not reached the operating pressure for the fans.
If you have a digital display you can monitor the gas pressure, by hidden menus in the display.
If the car was allowed to idle with the A/C on, with low refrigerant i would,nt expect the fans to kick in.
202's, 208's and 210's essentially share the same mechanicals, suspension set up, wiring etc. your car will or should operate the same as mine. If a 202, 210, 208 came without A/C fitted the twin fans are not fitted, hence they are not nessacary for engine cooling.

 

[turbopete]

the only digital display i have is the one where the mileage and outside temp is displayed, more or less identical in appearance to the ones in my w202's, but they didnt have aircon, hence the uncertainty. this is the first car ive owned with A/C

 

[television]

Hi,
I still maintain that these fans are primarily for the A/C. The fans may not be running as the refrigerant gas have not reached the operating pressure for the fans.
.

You are right Andy, they are mainly for the Aircon, running my 129 with the 2 stage fans, in the summer with the air con on and the roof down, they would run for 5 nins after turning off the engine