Aux Fan infront of Radiator
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Joined: Apr 2004
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From: Sydney, AU
1999 CLK 320 (Fathers); 2005 Jeep Wrangler Renegade (My Beast)
Aux Fan infront of Radiator
Hi there,
im continually having a problem with my car overheating... i.e. hitting 120C and above!!!!!
i dont think my aux fan is kicking in, how can i make it run even at a cold temp??
im continually having a problem with my car overheating... i.e. hitting 120C and above!!!!!
i dont think my aux fan is kicking in, how can i make it run even at a cold temp??
MBWorld Fanatic!
Joined: Aug 2003
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From: Vancouver, B.C.
2002 E55 AMG
Stop the car if the temp get's high and wait until you hear a click and a fan spinning. I don't know all the technical details. Oh and BTW, that fan makes a hideous noise when you rev the engine! 
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Joined: Feb 2002
Posts: 81
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From: Chicago
90 300e and B5 S4
I had the same problem on my 1990 300e. THe problem was both fan motors were broken. I don't know what caused it(maybe Chicago winters).
One way to test the fans is to disconnect the thermal switch and see/hear if the front fans kick on. Also check (with the engine cooled down) to see if the fans spin freely.
One way to test the fans is to disconnect the thermal switch and see/hear if the front fans kick on. Also check (with the engine cooled down) to see if the fans spin freely.
Newbie
Joined: Jul 2003
Posts: 24
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From: Norfolk VA
1987 300E
Ahhh, '87 300E... I can help now, since I just recently solved overheating problems on mine.
The thermal switch is on the air filter side of the head near the center of the engine next to the valve cover. There will be 3 wires. The two vertical sleeved posts are to the switch. Just jump them (to bypass the switch) with the engine running and the aux fax should run. That will tell you if it's the switch. If not you need to troubleshoot further (likely fan motor or wiring). My switch was bad. Cheap and easy to replace.
Also my viscous clutch was shot. With a cold engine there should be considerable resistance to turning with the engine off. It should couple on startup (it'll be louder) then loosen after startup. Look for oil leakage there. If the seal goes, so goes the fluid and it won't work right. If it's sitting idling where the engine starts getting hot you should also hear it couple. On mine I (very carefully!!) inserted a stick with it running and engine hot and was easily able to stop it. That showed it was bad.
After replacing the switch and clutch it stays cool now.
Also you should check the bearing behind the clutch & fan. It is known not to last long.
Good luck!
The thermal switch is on the air filter side of the head near the center of the engine next to the valve cover. There will be 3 wires. The two vertical sleeved posts are to the switch. Just jump them (to bypass the switch) with the engine running and the aux fax should run. That will tell you if it's the switch. If not you need to troubleshoot further (likely fan motor or wiring). My switch was bad. Cheap and easy to replace.
Also my viscous clutch was shot. With a cold engine there should be considerable resistance to turning with the engine off. It should couple on startup (it'll be louder) then loosen after startup. Look for oil leakage there. If the seal goes, so goes the fluid and it won't work right. If it's sitting idling where the engine starts getting hot you should also hear it couple. On mine I (very carefully!!) inserted a stick with it running and engine hot and was easily able to stop it. That showed it was bad.
After replacing the switch and clutch it stays cool now.
Also you should check the bearing behind the clutch & fan. It is known not to last long.
Good luck!
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MBWorld Fanatic!
Joined: Aug 2002
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From: Germany
'00 S320 W220, '98 A160 W168/ sold in 2005 '86 260 E W124 '90 260E W124
Re: Aux Fan infront of Radiator
Originally posted by spida
Hi there,
im continually having a problem with my car overheating... i.e. hitting 120C and above!!!!!
i dont think my aux fan is kicking in, how can i make it run even at a cold temp??
Hi there,
im continually having a problem with my car overheating... i.e. hitting 120C and above!!!!!
i dont think my aux fan is kicking in, how can i make it run even at a cold temp??
Newbie
Joined: Jul 2003
Posts: 24
Likes: 0
From: Norfolk VA
1987 300E
The electric fan is a two speed and had two controls to activate.
1. The water temp switch on the head that I previously mentioned will activate the fan on high speed when water temp hits approximately 107 deg. C.
2. When A/C pressure hits 16 bar the fan will activate on low speed.
This is per the factory CD specs, not an opinion.
1. The water temp switch on the head that I previously mentioned will activate the fan on high speed when water temp hits approximately 107 deg. C.
2. When A/C pressure hits 16 bar the fan will activate on low speed.
This is per the factory CD specs, not an opinion.
MBWorld Fanatic!
Joined: Aug 2002
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From: Germany
'00 S320 W220, '98 A160 W168/ sold in 2005 '86 260 E W124 '90 260E W124
JoeR, your are right, but I dont know excactly the year MB switched to a "two fan in parallel design" which only are activated by the pressure switch on top of the dryer. It is in the 90' models, but as I said dont when it started.
Newbie
Joined: Dec 2003
Posts: 10
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From: Birmingham AL
1990 300E
My 1990 300E has the two aux fans.. Having some trouble with them. In the past (and I'm just basing this on memory) the left side fan came on when ever the A/C was turned on and the right fan would cycle on and off. I guess the right fan is controled by the head temp switch. One question I have, where are the relay(s) for these fans located?
MBWorld Fanatic!
Joined: Aug 2002
Posts: 1,005
Likes: 33
From: Germany
'00 S320 W220, '98 A160 W168/ sold in 2005 '86 260 E W124 '90 260E W124
Originally posted by BamaMB
My 1990 300E has the two aux fans.. Having some trouble with them. In the past (and I'm just basing this on memory) the left side fan came on when ever the A/C was turned on and the right fan would cycle on and off. I guess the right fan is controled by the head temp switch. One question I have, where are the relay(s) for these fans located?
My 1990 300E has the two aux fans.. Having some trouble with them. In the past (and I'm just basing this on memory) the left side fan came on when ever the A/C was turned on and the right fan would cycle on and off. I guess the right fan is controled by the head temp switch. One question I have, where are the relay(s) for these fans located?
