C250TD aircon no fans

[matlockmark]

As this is my first post to this forum I'd like to say thanks to those who contribute to it - I have found it very helpful and entertaining.

Currently I am investigating a problem with the aircon on my 1998 C250TD (W202). The aircon works slightly, but does not give the icy blast that I would expect. In checking this out I noticed that the two electric fans in front of the condenser never ever seem to spin. From previous posts on this forum I believe that these fans cut in when the pressure in the aircon system gets too high or when the engine temperature rises too high.

That said, would I expect these to operate under normal driving conditions? I've opened the bonnet on a hot (30 deg C) day in stop-start traffic when the aircon has been on, but still no action from them. Could this possibly be the cause of the problem?

I would be very grateful for any help

Thanks

 

[DieselE]

As this is my first post to this forum I'd like to say thanks to those who contribute to it - I have found it very helpful and entertaining.

Currently I am investigating a problem with the aircon on my 1998 C250TD (W202). The aircon works slightly, but does not give the icy blast that I would expect. In checking this out I noticed that the two electric fans in front of the condenser never ever seem to spin. From previous posts on this forum I believe that these fans cut in when the pressure in the aircon system gets too high or when the engine temperature rises too high.

That said, would I expect these to operate under normal driving conditions? I've opened the bonnet on a hot (30 deg C) day in stop-start traffic when the aircon has been on, but still no action from them. Could this possibly be the cause of the problem?

I would be very grateful for any help

Thanks

If the fault was with the fans, I would expect the air con to run normally for a while then trip out. If it's running but not as cold as you would expect, my first thought would be lack of gas. In either case, I don't think this is something you're likely to be able to fix yourself.

 

[matlockmark]

That's a good point, although you have jogged my memory. A couple of weeks ago on a long journey, as the outside temperture got hotter the aircon seemed to get even less effective. Perhaps this could have been the lack of fan power, but it could be just that the aircon is not working very well. Since then my journeys have been only 30 mins long so I guess this wouldn't happen.

As you suggest, I think the next step is a visit to the local aircon specialist.

 

[tamrsoft]

For aircon to work efficienctly you must have reasonable air flow passing through condensing radiator in order to cool the compressed refrigerant (which is already hot from heat extracted from the cabin). This would normally happen when the car is moving forward at a reasonable speed, when the car is stationary or very slow moving, the fan should supplement this air flow. On my car, the fan always cuts in when the aircon is switched on irrespective of road speed. Sounds like you need a specialist to check this out.

 

[paulmb]

how many fans have you got at the front...........if you have two then one is for the a/c....i may b wrong and if so, someone correct me.........

i had a similar problem..........

best way to check is to run 12v direct to the fans and see if they spin...

you will need to get it hooked upto the diagnostics....mine turned out to be the coolant pressure switch, which is located on the side of the receiver/dryer unit....

 

[silverarrow]

check your fan control relay under the lt wing
known fault i am not 100 % if the 250 has the same as a petrol
but i have had 2 fail one on a c200 and one on a c220 cdi
have you had high engine temp ie above 85/90 ??? even in heavy traffic

 

[Dieselman]

If the aircon isn't outputting cold air from the vents when on recirc then it sounds like the gas pressure may be low.

The fans will only run if the coolant temperature rises, the aircon condensor temperature rises and the system pressure rises.

There may be nothing wrong, MB aircon is not really cold.

Park the car up and place a thremometer into the dash vents, turn the aircon on and the system to recirc. Run the engine for 30 mins, the air should come out of the vents at about 6 degrees.

 

[matlockmark]

Further findings

Thanks for all the replies - there are certainly plenty of things to consider.

A local aircon expert came round to investigate the problem. We did the thermometers in the dash vents test and found that the air was hardly being cooled at all. I had thought that the aircon was working better than this, but I was probably being fooled by the windchill caused by the air flow with the blower on full (helped by the fact that I recently changed the pollen filter).

He found that there was plenty of gas in the system, but that it was hardly being circulated at all - there was no change in the readings on his high and low-side pressure gauges with the compressor on or off. The compressor does seem to be turning when the electromagnetic clutch is engaged, but it is making a nasty sort of whirring sound. I hadn't noticed this before, but now I have it seems to be getting louder and louder.

The aircon chap thinks that either there is a blockage in the system (rare, as an effective compressor would probably clear this), or there is a fault with the electromagnetic clutch (it is able to turn the compressor, but with insufficient speed or power) or a fault with the compressor itself.

Anyway, the upshot is that I booking the car in to get him to fully investigate and fix the problem. I will post the result when this is complete.

Thanks again for your suggestions

 

[mstar01]

hi guys a dumb question but am i right in saying that the C250 TD 1998 sport, doesn't have a specific "AC" button like other makes? or does it just have bog standard cold air dialing controls like cars without AC

 

[Glenn Smith]

The C class has either semi or fully automatic system, the semi has the temp wheels and the aircon always switches on unless you press the economy switch the sytem then still controls temperature automaticaly, but with out the cooling. Also your aircon chap doesn't know too much, a blockage would cause high, high side readings and low, low side readings and a noisy compresssor the most likely place for a blockage is in the expansion valve, fitted to the evaporator. Low gas charge wuold cause low readings on both sides, low speed compressor on the 250td will cuase the compressor to switch off. I would say you're either low on charge or the compressor is faulty, outlet air temp is dependant on ambient to a certain extent, expect 3-4degrees c at 20 deg ambient, doors closed on recirc, fast idle mid way fan speed.

 

[matlockmark]

I would say you're either low on charge or the compressor is faulty

You are right - the compressor was faulty. It has now been replaced and the aircon is now working better than it has ever worked before. Even the two front fans now spin

Unfortunately a few hours after the compressor was replaced the heater blower motor packed up

However after stretching the brush springs slightly it now works reliably - just as well during the current heatwave

Only the rust to sort out now to make the car perfect....

 

[silverarrow]

get your bushes from a washing machine repair man at about a £5

 

[reflexboy]

There may be nothing wrong, MB aircon is not really cold.

.

Mine is like ice-Lurvely