auxialiary fan question

[satrat]

Auxiliary fans were not coming on and whenever temp indication went up, I used to turn the heater on and this trick worked. Then I read from the forum that sometimes you can fix the relay by "tapping" on it. Believe it or not, I am one step closer.

Refer to the graphic for the relays. I "tapped" the green relay #0015429619 and tested for the aux fans. When the temp reached above 100, aux fans did not work. I turned the engine off and restarted and wandabaah, both fans turned on for few seconds, I noticed temp coming down. I let the temp go up again and aux fans did not work. Once again, I turned the engine off and restarted, and no surprise, aux fans came on. I think that I am one step closer to solving this problem.

This test reveals that fan motors are working but something is not working right.

Would someone please inform me what this stage one and stage two mean for our cars. Also what do I need to do that the fans automatically start when they need to be started.

[liquidusculade]

have you replaced the relay yet?

[satrat]

no, i have not
i like to know if relay is the culprit.

[jlomon]

The auxiliary fan system uses two electric fans working together. These fans operate at two preset speeds (stages) and are triggered to operate under two different conditions. Each stage has its own relay to control operation.

The green relay (stage 2) is connected to the air conditioning system - they turn the fans on at the high speed setting whenever you turn on the a/c. The blue relay is the one you are interested in - it controls the stage 1 (low speed) setting that should turn the fans on whenever your engine coolant temp reached ~ 100C. There is a 15 amp fuse in that relay that is prone to failure. Pull the fuse and have a look before you go replacing relays.

Edit - if your fuse is indeed broken, you may want to consider upgrading it to a 25 amp fuse as per post 43 in this thread here - http://www.benzworld.org/forums/w202...nfusion-5.html

[satrat]

fuse upgrade!!!! wow, that is news to me and what a cost-effective option to rule out the potential problem. I will change the fuse to 25 today and will update

Thanks jlomon

[satrat]

wallah!!!!
it worked, cost was $3.23 AAAAND aux fan automatically comes on at 105 degrees

Thanks again

[Fusion.C280]

105 seems a lot to me, maybe you should replace your thermostat.
I think the fans should kick in a bit under 100°.

[satrat]

Thermostat Specifications: Start Of Opening 85 - 89°C, Maximum Opening 102°C
I will change thermostat with 110 200 05 15 today and update
Yours c280 is exactly same as mine, how is your temperature gauge functioning?

[jlomon]

AFAIK the fans should come on when the thermostat reaches that maximum open point at 102C. The needle on your temperature gauge is not precise enough for you to be able to see the difference between 102 and 105. I wouldn't worry about that too much, honestly.

[Metafly]

Mine kicks on at about 87, thanks to a very cool, cool harness Found here (1/3 way down page):http://www.k6jrf.com/MB_S500.html