Fan Relay question

[trueog]

Hey guys, I'm starting to have another problem with my C220. In the relay box, I've noticed one of the relays, which I beleive is for the fan....and contains a fuse, it keeps blowing the fuse. I was wondering if anyone else has experianced this problem also and what generally causes it? I've changed the fuse in the relay now for the third time, and i'm starting to wonder if my relay has toasted out. Anyone know how to test to relay, or any idea's what's happnening? thanks

[stevebfl]

Really, really, unlikely that the fuse would blow due to a defective relay. The relay only is a fused connection on the circuit in question. Blaming the relay would be similar to blaming the fuse box for the reason the a fuse would blow. Not unheard of, but almost.

The fuse blows because the circuit uses more current than the fuse is rated for. This means that the device that the fuse powers is using too much current or the circuit is shorted somehow.

[Arthur Dalton]

Which fan and what amp fuse????????

[trueog]

Its the Aux.Fan relay I believe. Its in the relay box under the fuses which are under the hood. Its a blue relay, which when searched for by mercedes is superceded by the green relay which is also used as a fuel pump relay in the trunck. This is what I was told over the phone. The blue relay under the hood keeps blowing its fuse, and the fuse is a blue 15A fuse also. Has anyone else had similar probs? Thanks guys.

[Arthur Dalton]

There are two aux fan relays
A blue and a green .
One is for low fan [ a/c activated] and the other is high fan [ coolant temp activated]
Benz allows uping the 15A to a 25 A.

Also be sure someone has not switched the rekays . as they fit either base.................

[trueog]

Hey buddy, thanks for the response. Yeah in my relay box there is a green relay and the blue one which is the one blowing the fuses. Would you think its a defective relay? or defects causing it to blow out the fuse? since the fuse has blown 3 times, I'm just worried that the relay might be toast?? Is the blue relay for the low fan or high fan? Also another thing is, my car is starting to lose coolant and needs topping up around every 10 days. There's no leaks that I seem to see, and there's never coolant hanging around the engine or the ground. After a fast drive on the freeway for 10 minutes, and stopping at a drive thru....I can smell boiling coolant...like vapours. Do you think it might be linked to a defective relay?

Also, so I should chance the 15A fuse to a 25A on the blue relay?

Thanks bro

Originally Posted by Arthur Dalton

There are two aux fan relays
A blue and a green .
One is for low fan [ a/c activated] and the other is high fan [ coolant temp activated]
Benz allows uping the 15A to a 25 A.

Also be sure someone has not switched the rekays . as they fit either base.................

[jlomon]

Arthur was kind enough to walk me through this whole relay thing last summer on my C280. The blue is the low speed relay and is the one that can be changed from 15 to 25. This is only related to your air con, so your high speed fan setting still works when the coolant temperature reaches 100-105 (I don't remember exactly what temp).

[Arthur Dalton]

You are assuming a bad relay, but I doubt it.. The relay is simply a switch for circuit power feed.
Take the fuse out of the relay and replace it with a couple of spade connectors and then use an amp meter across those for a circuit draw reading.
If it is high,the first suspect would be the pre-resistor behind the headlamp .

[trueog]

Hey thanks for the advice arthur. But what you just said is beyond my understanding..lol. Also the jlomon and you're relay talk and walk through, is that thread still alive? If you could share it with me, that would be nice.

Thanks