At What Temperature electric fan designed to cut in?

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W L Ow

Active Member
Joined
Feb 16, 2005
Messages
87
Location
Kuala Lumpur, Malaysia
Car
C200-202(A) 1997
My 1997 202 with air conditioner and a electric cooling fan had engine over heating problem recently. The water pump was replaced with a new one last week. Now with the air conditioner off and idling starting from a cold engine, the electric fan does not cut in until the temperature meter reads above 95 deg C. The fan seems to run at low speed when it cuts in. Also tried switching on the air conditioner idling with a cold engine. The fan cuts in immediately. The car now runs at about 95 deg C as compared with slightly above 80 deg C before. The fan and the fan control units were replaced about 60K KM ago.

Is the fan cutting in at 95 deg C normal? Is the electric fan or the controller on the way out? Is the themostat the culprit?

Thanks in advance
 
You should also have an engine cooling fan mounted behind the radiator. It probably has a viscous clutch fan which may not be working. the electrical fan/fans in front of the radiator are for the airconditioning only.
edit :- how many fans have you got,what type, and where are they? just in case I am speaking rubbish:eek:
 
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Standard reply for this, Engine visco and electro fans cut in at 85c. electric fans on the rads cut in at 100c.

Malcolm
 
grober said:
You should also have an engine cooling fan mounted behind the radiator. It probably has a viscous clutch fan which may not be working. the electrical fan/fans in front of the radiator are for the airconditioning only.
edit :- how many fans have you got,what type, and where are they? just in case I am speaking rubbish:eek:

As you know I am doing the 24V conversion and I had a viscous fan on my old 12v engine, but 2 electric fans on the new 24V lump which had aircon, I am going to use the electric fans in the conversion but what type is better??
 
As you know I am doing the 24V conversion and I had a viscous fan on my old 12v engine, but 2 electric fans on the new 24V lump which had aircon, I am going to use the electric fans in the conversion but what type is better??

My guess and its only a guess is that the dual electric fans would give better temperature control than the viscous fan. The viscous fan would give cruder control but probably more robust in the long term. They do go wrong tho or get cruded up. remember to always store the viscous coupling in a vertical position if its off the car.
 
The car only has one factory fitted electric fan. There is no viscous fan. The air-con is also factory fitted. As you all know, Malaysia where I am located has very hot climate all year round. Since the fan and air-con are all factory fitted locally in the assembly line, I believe the fan is designed to be sufficient to cool the air-con and the engine not withstanding the hot climate.

The entire anti-freeze (for rust prevention in our case) coolant was replaced together with the pump. No air lock

Although the car now cruises at about 95 deg C. I noticed yesterday that it may drop down to below 80 cruising down hill with the air-con switched on. I guess the high cruising temperature is due to the cooling fan not blowing hard enough unless assisted by the slope. I guess I have to replace the electric fan or/and the fan control unit. Any advice before I waste my money and effort on either one or both of them if they are not the culprit?

If the thermostat is designed to open at 80+ deg C, I suspect that the themostat is also not closing properly causing temp to drop below 80. Is there any harm in not replacing the themstat since it does not cause overheating?

Thanks in advance.
 
blocked rad or faulty pressure cap.

sounds as if your cooling system has been "traumatised" by the overheating incident. Replacing the thermostat would do no harm and eliminate it as a source of your problem. Make sure you get the one recommended for your geographical area. The symptoms you describe
Although the car now cruises at about 95 deg C. I noticed yesterday that it may drop down to below 80 cruising down hill with the air-con switched on. I guess the high cruising temperature is due to the cooling fan not blowing hard enough unless assisted by the slope.
are typical of a partially choked radiator. Sometimes after a "overheating incident" or a coolant drain sediment dries into the radiator passages reducing the effective cooling area. Driving along the highway should provide enough engine cooling via the flow of air thro the radiator as the car drives along without the help of the fan. The other possibility is a failure to pressurise the system. This is normally due to a defective pressure cap. What EXACTLY caused the first overheating??
 
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Hi Graeme,

The earlier overheating was due to coolant leaking between the casing and the pully of the water pump. The rad cap was replaced together with the water pump.

What is the normal life span of a electric fan motor? You may be right about the radiator clocking up but I guess it is cheaper to deal with the electric fan motor first.

Cheers
 
W L Ow said:
Hi Graeme,

The earlier overheating was due to coolant leaking between the casing and the pully of the water pump. The rad cap was replaced together with the water pump.

What is the normal life span of a electric fan motor? You may be right about the radiator clocking up but I guess it is cheaper to deal with the electric fan motor first.

Cheers

If its on the original fan then its 9 years old. It has perhaps had quite a hard life in your climate! You could try rotating/rocking the fan shaft by hand to check for binding or bearing/bush wear.
Your symptoms on the open road do point to a choked radiator as the more likely cause of your hot running however IMHO
 
W L Ow,

Although the car now cruises at about 95 deg C. I noticed yesterday that it may drop down to below 80 cruising down hill with the air-con switched on.
This doesn't seem to be right. Once the engine has warmed up, it should never drop below 80C (especially in Malaysia). I think your thermostat is not closing properly and letting too much coolant flow causing temps below 80C when the engine is at low power. Also I think your thermostat is not opening fully and restricting flow allowing the temp to climb to 95C+ when your engine is at higher power.

I think your thermostat is basically non-functional. The good news is that thermostats are cheap and very easy to change (a small loss of coolant will need to be replaced and the system burped of air voids).

Good luck and let us know the outcome.
 
I suspect the thermostat has been removed in one of the car's earlier trip to the garage because I found out today that the upper radiator hose exiting from the thermostat became hot immediately after the engine is started from cold. I shall open it up this week end. If the thermostat is really not there, I shall install a new one. But that will not solve the high cruising temperature problem which I think has also affacted the air-con cooling capacity. Is there an effective way to clear the blockage in the radiator?

Thank you in advance
 
If the thermostat is missing then some of the coolant can bypass the radiator altogether and this might explain the reduced cooling efficiency!! I would try a new thermostat first and see what happens. You can try "backflushing" the radiator by reversing the normal fluid flow direction. Remove the radiator turn it upside down and with a water hose introduce water into the lower (outlet) connector and give it a thorough wash out. this sometimes works but the best solution is to replace the entire radiator.

In this case tho try replacing the thermostat first before anything else.

edit:- the thermostat for my w124 car with the 220 version of your engine came as a complete housing/thermostat unit part no A 111 200 09 15 opening temp 87c dont know if this the same for a C class 200 or the 87c temp is suitable for Malaysia
 
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W L Ow
I am from Klang.
You should buy your parts from Kerasjaya in Taman Maluri.
The outlet is run by one Ah Kow and family.
Very reasonably priced original MB parts.
I have been buying parts from them for the 20 years or so.
Shan.
 
fan control relays have been modifired to make them kick in at a lower temp and also they are waterproof ???????? umm a good way to sell more relays at £105 in the uk
 
Hi Shan,Welcome to the club. Do you have the address or phone number of the part dealer at Taman Maluri? I normally get mine from Swan Huat at SEA Park PJ.

Thanks Silverarrow, It may be good to lower the radiator temp a little in my location so that the air-con works better. But lowering the engine temp may increase fuel consumption and pollution.

Thanks for the idea anyway.

Cheers
 
As suggested, I replaced the thermostat. The thermostat rating is 71 deg C much lower than 80 + used in colder locations. It only cost the equivalent of 10 sterling pound here. The cruising temperature did not come down.

Tried replacing the electric cooling fan but the local part dealer does not have stock. any way it costs equivalent of more than 100 sterling pound. Opened up the old electric fan (see picture attached) and did the followings:

Clean up the gaps between the copper elements of the commutator which is filled with graphite and copper powder wound off from the carbon contacts.

Blow clean the interior of the motor with compress air.

Greased and oil the end of the rotor shaft

The electric fan now run faster and the temperature is slighly above 80 deg C most of the time.

On removing the fan housing, discovered a plug which is not plug into anything (see picture). Does anyone know what the plug is for? It could have been unplugged by the garage when the air con compressor was replaced recently.

Thanks for all the suggestions

Cheers
 
Here are the pictures I have overlooked.
 

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Sorry cant shed any light on the mystery plug.:confused:
 

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